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Toolora Blog
Tool deep-dives, workflow notes, longform SEO posts. Roughly weekly, English and Chinese authored separately.
Base64 in Practice: Image Data URIs, JWT Decoding, and localStorage Compression
Three real frontend scenarios where Base64 actually matters — embedding images as data URIs, manually decoding JWT payloads, and storing compressed binary data in localStorage. Code you can run right now.
Read moreHealth & Wellness 33
- · Li Lei
The Wilks Score Explained: Comparing Powerlifting Strength Across Bodyweights
How the Wilks score ranks powerlifters fairly across bodyweights, why raw totals favor heavier lifters, and how the coefficient normalizes a total.
#powerlifting#wilks score#strength trainingRead more - · Li Lei
How a Weight Loss Tracker Reads the Trend Beneath Your Daily Scale Noise
A weight loss tracker turns noisy daily weigh-ins into a clear trend. Learn why the moving average matters, what a safe rate looks like, and the calorie math behind it.
#weight loss#calorie deficit#healthRead more - · Li Lei
How Much Water Should You Drink? A Water Intake Guide by Body Weight
Work out your real daily water intake by body weight and activity, why the 8-glasses rule is a myth, and how to adjust for heat and exercise.
#hydration#water intake#healthRead more - · Li Lei
Waist-to-Hip Ratio: The One Number That Reads Where Your Fat Lives
A plain guide to waist-to-hip ratio: how to measure it, the WHO risk thresholds by sex, why it beats BMI for fat distribution, and apple vs pear shape.
#health#body-composition#calculatorsRead more - · Li Lei
The Waist-to-Height Ratio: One Number That Beats BMI for Belly Fat
Your waist-to-height ratio is waist divided by height. Keep your waist under half your height, learn why WHtR spots central fat BMI misses, and the thresholds.
#health#waist-to-height-ratio#body-compositionRead more - · Li Lei
VO2 Max Explained: How to Estimate It From a 12-Minute Run and What Your Number Means
Estimate VO2 max from a Cooper 12-minute run or your resting heart rate, read it by age and sex, and learn the training that actually moves the number.
#fitness#vo2-max#runningRead more - · Li Lei
TDEE Explained: Turn Your Daily Burn Into a Calorie Target
How TDEE works — BMR times an activity factor — and how to use it to set safe calorie targets for cutting, maintaining, or a lean bulk.
#tdee#calorie deficit#nutritionRead more - · Li Lei
Steps to Distance: How to Turn a Step Count Into Real Miles and Km
Convert steps to distance with one formula, estimate your stride from height, learn what 10,000 steps really cover, and calibrate your own stride in two minutes.
#steps to distance#steps to miles#stride lengthRead more - · Li Lei
How Many Stair Climbing Calories You Actually Burn (And Why Stairs Beat Flat Walking)
A clear, honest guide to stair climbing calories — the MET-based formula, a worked 70 kg example, and how weight and pace change the number you burn.
#fitness#calories#stair climbingRead more - · Li Lei
Sleep Debt Is Real: How the Hours Add Up and Why One Weekend Won't Clear It
Sleep debt is the gap between the sleep you need and the sleep you get, accumulated night by night. Here's how to measure it and build a recovery plan that works.
#sleep#health#productivityRead more - · Li Lei
Sleep Cycle Calculator: Find a Bedtime That Wakes You Between Cycles
How to time sleep around 90-minute cycles so your alarm rings between cycles instead of mid-deep-sleep. Count back from your wake time and add a fall-asleep buffer.
#sleep#sleep cycle#bedtimeRead more - · Li Lei
How to Budget Your Daily Screen Time Before a Year Quietly Disappears
Budget daily screen time, see how hours per app add up over a week and a year, set honest limits, and learn what those hours could have bought you instead.
#screen time#digital wellbeing#habitsRead more - · Li Lei
How a Running Pace Calculator Turns a Goal Time Into a Number on Your Watch
Pace, time, and distance are three sides of one equation. Learn how to set a goal race pace, convert min/km to min/mile, and read your splits with confidence.
#running#pace#marathonRead more - · Li Lei
Protein Intake by Body Weight: How Many Grams You Actually Need Per Day
Work out your daily protein intake from body weight and goal. Why active people aim for 1.6-2.2 g/kg, not the 0.8 g/kg RDA, and how to split it across meals.
#protein intake#nutrition#muscle gainRead more - · Li Lei
How Much Pregnancy Weight Gain Is Healthy? The IOM Ranges by BMI
Healthy pregnancy weight gain depends on your pre-pregnancy BMI. A plain-English look at the IOM ranges, trimester pacing, and twins versus a singleton.
#pregnancy#weight gain#healthRead more - · Li Lei
Lean Body Mass, Explained: Boer, James, and Why That Number Drives Your Protein and Your Dose
What lean body mass actually measures, how the Boer and James formulas estimate it, and why LBM, not total weight, sets protein targets and clinical dosing.
#lean body mass#fitness#healthRead more - · Li Lei
Intermittent Fasting Schedules Explained: 16:8, 18:6, and OMAD
A plain guide to intermittent fasting schedules — how 16:8, 18:6, and OMAD windows work, what happens by fasting stage, and how to ease in safely.
#intermittent fasting#16:8#omadRead more - · Li Lei
Ideal Weight Formulas Explained: Devine, Robinson, and Hamwi
How the Devine, Robinson, and Hamwi ideal weight formulas turn height and sex into a number, and why frame size and muscle make them rough guides.
#ideal weight#health#calculatorRead more - · Li Lei
How Training Heart Rate Zones Actually Work (and the Fat-Burn Myth)
A plain guide to the five heart rate zones, the 220 minus age max-HR estimate, what each zone trains, and why the fat-burning zone is half a myth.
#fitness#running#heart rateRead more - · Li Lei
FFMI Explained: Why Fat-Free Mass Index Beats BMI for Lifters
A practical guide to the Fat-Free Mass Index (FFMI) for lifters: how to compute it from weight, body fat and height, the natural ceiling near 25, and normalized FFMI.
#ffmi#fat-free mass index#bodybuildingRead more - · Li Lei
How to Estimate Calories Burned by Activity Using MET Values
Estimate calories burned from any workout using MET values, your weight, and duration. The textbook formula, a worked example, and how to compare exercises fairly.
#fitness#calories#calculatorsRead more - · 李雷
How a Calorie Calculator Turns BMR and TDEE Into a Daily Target
Learn how a calorie calculator works: estimate BMR with Mifflin-St Jeor, apply TDEE activity multipliers, set a deficit or surplus, and split your daily macros.
#calorie#nutrition#fitnessRead more - · Li Lei
How Long Caffeine Really Stays in Your Body: A Half-Life Guide
Caffeine has a half-life of about 5 hours, so an afternoon coffee lingers until bedtime. Learn to estimate residual caffeine, set safe limits, and time your last cup.
#caffeine#sleep#healthRead more - · Li Lei
How to Estimate Body Fat Percentage From a Tape Measure
Estimate body fat percentage with the US Navy tape method versus BMI-based formulas — what the number means, healthy ranges by sex, and a worked example.
#body fat#body composition#fitnessRead more - · 李雷
BMI Calculator Guide: The Formula, WHO Thresholds, and Where BMI Breaks Down
How a BMI calculator works: the metric and imperial formula, the WHO category thresholds, why Asian-Pacific cutoffs are lower, and the muscle-mass cases where BMI quietly lies.
#bmi#health#calculatorRead more - · Li Lei
How to Read a Blood Pressure Category: Systolic, Diastolic, and the AHA Bands
Learn what your blood pressure numbers mean. How systolic and diastolic map to the AHA categories, why the higher number wins, and a 135/85 worked example.
#blood pressure#health#hypertensionRead more - · Li Lei
Estimating Blood Alcohol Content: How the Widmark BAC Formula Works
How a blood alcohol content estimate is built from the Widmark formula, why body weight, sex, and time matter, what 0.08 means, and why it is never a fit-to-drive verdict.
#bac#blood alcohol content#widmark formulaRead more - · Li Lei
A1C to Estimated Average Glucose: How the Conversion Works
How A1C converts to estimated average glucose (eAG), what A1C measures, the formula, ADA thresholds, and a worked 7% example. Informational, not medical advice.
#a1c#estimated-average-glucose#blood-glucoseRead more - · Toolora
How to Use a Safe Period Calculator Without Mistaking It for Birth Control
A practical guide to reading safe period calculator results, with a real date example, fertility window math, and clear limits for contraception and irregular cycles.
#health#calculator#fertilityRead more - · Lei Li
Lower Back Pain Acupressure: BL40, BL23, and the Classical 「腰背委中求」 Rule
Using the Chinese Acupoint Locator to find the four-point self-acupressure pattern for non-specific low back pain — BL40 Weizhong, BL23 Shenshu, GV3 Yaoyangguan, BL25 Dachangshu. With the WHO 2008 codes, a real lookup output, and a first-person field test after a six-hour drive.
#tcm#acupressure#lower-back-painRead more - · Lei Li
Finding LI4 in Three Seconds: Using a Chinese Acupoint Locator the Way a TCM Student Actually Looks Things Up
A practical walkthrough of looking up Chinese acupoints by symptom — the headache five, the back-pain pair, and what 脐下 3 寸 really means. With the WHO 2008 numbers, the safety line, and why LLM-generated TCM data is the wrong answer.
#tcm#acupressure#referenceRead more - · Lei Li
Building a Two-Minute Eye-Strain Routine with the Chinese Acupoint Locator
Five acupressure points I press twice a day during long screen sessions, looked up by symptom in the Chinese Acupoint Locator. With the WHO 2008 codes, the classical locations, and the blink-rate evidence behind why this matters.
#tcm#acupressure#eye-strainRead more - · Lei Li
16:8 vs OMAD: An Intermittent Fasting Beginner Guide (with the Actual Science)
What the 2018 Anton review and the Sutton early-time-restricted-eating trial actually show, plus a practical comparison of 16:8 and OMAD — who each is for, who shouldn't try them, and the four mistakes beginners make.
#health#fasting#tutorialRead more
Math & Puzzles 55
- · Li Lei
Weighted Average Explained: When a Plain Mean Lies to You
A weighted average counts some numbers more than others. Learn the formula, see a worked grades example, and know when a simple mean misleads you.
#weighted average#statistics#mathRead more - · Li Lei
Sin, Cos, Tan Without the Panic: A Trigonometry Calculator Guide
A practical walk through sin, cos, tan and their inverses, SOH-CAH-TOA, degrees vs radians, and solving right triangles, including a worked angle-of-elevation height problem.
#trigonometry#sin cos tan#right triangleRead more - · Li Lei
How to Solve Any Triangle: A Practical Triangle Calculator Guide
Solve a triangle from given sides and angles using the law of sines, law of cosines, and area formulas — with a worked example and real layout uses.
#geometry#trigonometry#mathRead more - · Li Lei
Sphere Volume and Surface Area: The Two Formulas and Where They Come From
How to find the volume and surface area of a sphere from radius or diameter, what the formulas mean, a worked example, and real uses from tanks to planets.
#geometry#math#calculatorRead more - · Li Lei
Special Numbers Explained: A Number Checker for Primes, Perfects and Palindromes
Learn what makes a number prime, perfect, palindrome, Armstrong, Fibonacci or triangular, then test any integer against all of these properties at once.
#number theory#math#educationRead more - · 李雷
How to Find the Slope Between Two Points (Plus Angle, Distance, and Line Equation)
A practical guide to the slope formula: turn two points into slope, angle of inclination, distance, midpoint, and the y = mx + b line equation, with a worked example.
#slope#geometry#mathRead more - · Li Lei
How to Simplify Fraction Values to Lowest Terms
Reduce any fraction to lowest terms by dividing by the GCD, convert improper fractions to mixed numbers, and learn why simplest form matters.
#fractions#math#lowest termsRead more - · Li Lei
Scientific Notation Explained: From Standard Form to a × 10ⁿ
How to convert between standard form and scientific notation, count the exponent by moving the decimal, handle huge and tiny numbers, and read E-notation in code.
#scientific notation#standard form#significant figuresRead more - · 李雷
How to Use a Scientific Calculator Without Getting the Wrong Answer
A practical scientific calculator guide covering trig, log, exponent, and factorial functions, operator precedence, degrees versus radians, and the memory keys most people misread.
#calculator#math#trigonometryRead more - · 李雷
Ratio Math Made Simple: Simplify, Solve, Scale and Split
Learn to simplify a ratio, solve a:b = c:x for the unknown, scale recipes or drawings up and down, and split a total by a ratio — with worked examples you can check by hand.
#ratio#proportion#mathRead more - · Li Lei
How to Solve Any Quadratic Equation: The Formula, the Discriminant, and the Parabola
A practical guide to solving quadratic equations: the quadratic formula, what the discriminant b²−4ac tells you, factoring vs formula, and reading the parabola vertex.
#math#algebra#quadratic equationRead more - · Li Lei
How to Find the Missing Side of a Right Triangle with the Pythagorean Theorem
Use a² + b² = c² to find the hypotenuse or a missing leg of a right triangle, with worked examples and real jobs like squaring a deck or sizing a screen.
#pythagorean theorem#right triangle#geometryRead more - · Li Lei
How a Prime Number Calculator Tests Primality and Lists Primes
How to check if a number is prime with trial division up to the square root, list primes with the sieve of Eratosthenes, and why primes anchor cryptography.
#prime numbers#number theory#cryptographyRead more - · Li Lei
Prime Factorization Explained: Factor Trees, Trial Division, and Why It Matters
A plain-English guide to prime factorization: the factor tree, trial division, the fundamental theorem of arithmetic, and how factors drive GCD, LCM, and fractions.
#math#number theory#prime factorizationRead more - · Li Lei
Converting Between Polar and Rectangular Coordinates Without the Sign Errors
A practical guide to converting between polar and rectangular coordinates with x=r cosθ, y=r sinθ, r=√(x²+y²), and atan2 for correct quadrants.
#math#coordinates#trigonometryRead more - · 李雷
How to Solve the 3 Percentage Questions That Trip Everyone Up
A clear guide to the three everyday percentage questions, plus why percentage change and percentage points are not the same number and where people go wrong.
#percentage#math#calculatorRead more - · Li Lei
How to Convert a Percent to a Fraction (and Back Again)
A plain-English guide to converting a percent to a fraction: put it over 100 and simplify, clear decimal percents, handle repeating ones, and read the triangle.
#math#fractions#percentagesRead more - · Li Lei
Pascal's Triangle Explained: How Every Number Adds Up to a Binomial Coefficient
How Pascal's triangle works, why each entry is the sum of the two above it, and how its rows give you binomial coefficients, powers of 2, and Fibonacci.
#math#combinatorics#binomial-theoremRead more - · Li Lei
The Multinomial Coefficient, Explained: Counting Ways to Split n Into Groups
How the multinomial coefficient n! / (k1! k2! ... km!) counts arrangements and group splits, with the MISSISSIPPI example and how it generalizes the binomial.
#combinatorics#multinomial coefficient#countingRead more - · Li Lei
Modulo, Explained: What the Remainder Really Means
A plain-English guide to the modulo operation: the remainder after division, where it shows up in code, and the negative-number sign trap that bites every programmer once.
#math#programming#moduloRead more - · Li Lei
Matrix Calculator: Add, Multiply, Transpose, and Invert Without the Arithmetic Headache
A practical guide to matrix operations — addition, multiplication, transpose, determinant, and inverse — why multiplication needs matching dimensions and isn't commutative.
#linear-algebra#matrix#mathRead more - · Li Lei
The Math Formulas Students Look Up Most: A Study Reference
A grouped study reference of the math formulas students look up most — areas, volumes, the quadratic formula, the Pythagorean theorem, slope, distance, and basic trig.
#math#study#formulasRead more - · Li Lei
Logarithm Explained: ln, log₁₀, log₂, and the Change-of-Base Formula
A plain-English guide to logarithms — the inverse of exponentiation, common and natural log, arbitrary bases, change of base, and where logs show up in pH, decibels, and code.
#math#logarithm#calculatorRead more - · Li Lei
The Geometric Sequence, Explained: nth Term, Sums, and the Infinite Series
How a geometric sequence works: the common ratio, the nth-term and sum formulas, when an infinite series converges, and where doubling and half-life math show up.
#math#geometric-sequence#sequencesRead more - · Li Lei
GCD and LCM, Explained: Euclidean Steps, Fractions, and Scheduling
A practical guide to computing GCD and LCM by hand and online: the Euclidean algorithm, the LCM = a×b/GCD shortcut, fraction reduction, and overlap scheduling.
#math#gcd#lcmRead more - · Li Lei
How to Find the Frustum Volume of Any Bucket, Lampshade or Hopper
The frustum volume formula explained in plain terms, with a worked bucket example and the real reason buckets, cups and hoppers are shaped this way.
#geometry#volume#frustumRead more - · 李雷
How to Add, Reduce, and Convert Fractions (With Worked Examples)
A practical guide to fraction arithmetic: add and subtract with common denominators, multiply and divide, reduce to lowest terms, handle mixed numbers, and convert to exact decimals.
#fractions#math#calculatorRead more - · Li Lei
Understanding the Fibonacci Sequence: From Two Seeds to the Golden Ratio
How the Fibonacci sequence works, why each term sums the previous two, how it reaches the golden ratio, and where it shows up in nature and code.
#fibonacci#sequences#golden-ratioRead more - · Li Lei
What a Factorial Is, Why n! Grows So Fast, and Where It Shows Up
A plain-English guide to the factorial: what n! means, why it explodes past 10!, its role in permutations, combinations, and probability, and why 0! = 1.
#math#factorial#combinatoricsRead more - · Li Lei
The Double Factorial Explained: What n!! Means and Where It Shows Up
A plain-English guide to the double factorial n!!, how it skips every other term, why it differs from n!, and where it earns its keep in math and physics.
#double-factorial#factorial#combinatoricsRead more - · Li Lei
How to Find All the Divisors of a Number (Count, Sum, and Factor Pairs)
Learn to list every factor of a number, count and sum its divisors, and tie it back to prime factorization, perfect numbers, and primes — with a worked example for 36.
#math#divisors#factorsRead more - · Li Lei
A Step-by-Step Derivative Calculator That Shows the Calculus, Not Just the Answer
Learn the power, product, and chain rules by watching a derivative calculator unfold every step. Worked examples, common slips, and how to read f'(x).
#calculus#derivatives#mathRead more - · Li Lei
Derangement Numbers Explained: Why !n Hovers Near 1/e
How derangements count permutations with no element in its original place — the recurrence, the hat-check problem, why !n/n! approaches 1/e, and Secret Santa odds.
#combinatorics#probability#permutationsRead more - · 李雷
How to Convert a Decimal to Fraction (Including Repeating Decimals)
Learn how to convert any decimal to fraction by hand: terminating decimals over powers of ten, repeating decimals with the let-x-equal trick, reducing with the GCD, plus real worksheet and measurement examples.
#math#fractions#decimalsRead more - · Li Lei
Cylinder Volume Made Simple: Tanks, Pipes and Containers from Radius and Height
How to compute cylinder volume and surface area with V=πr²h, size tanks and pipes, turn base area times height into litres or gallons, with a worked example.
#cylinder#volume#geometryRead more - · Li Lei
Coordinate Distance Made Simple: Finding the Distance Between Two Points
How to measure distance between two points, from the flat Euclidean formula to the Haversine great-circle method for latitude and longitude on a real, curved Earth.
#geometry#geospatial#mathRead more - · Li Lei
The Continued Fraction, Explained: How [a0;a1,a2,...] Finds the Best Fraction for Any Number
How a continued fraction expands any number into [a0;a1,a2,...], why its convergents give the best rational approximations, and where 22/7 for pi comes from.
#continued fractions#rational approximation#number theoryRead more - · Li Lei
Cone Volume and Surface Area, Worked Out Without the Guesswork
How to find the volume, slant height, and surface area of a cone, with the three formulas, a clean worked example, and real uses from funnels to traffic cones.
#cone#geometry#volumeRead more - · Li Lei
Complex Numbers Made Practical: Arithmetic, Modulus, and the Polar Form
A working guide to complex number arithmetic — add and multiply a + bi, find modulus and argument, switch to polar form, and see where engineers use it.
#complex numbers#math#polar formRead more - · Li Lei
Completing the Square, Step by Step: From ax² + bx + c to Vertex Form
Learn completing the square the way it actually works: factor a out, halve the middle coefficient, fold the perfect square, and read the vertex off a(x − h)² + k.
#algebra#quadratics#completing-the-squareRead more - · Li Lei
Combinations vs Permutations: When Order Matters and How to Count It
A plain-English guide to combinations vs permutations, the nPr and nCr formulas, and worked lottery, password, and committee examples you can recompute yourself.
#math#combinatorics#permutationsRead more - · Li Lei
How a Circle Calculator Turns One Number Into Four
A practical guide to solving any circle from a single measurement: radius, diameter, circumference, and area, with the formulas, a worked example, and real uses.
#geometry#math#calculatorRead more - · Li Lei
The Birthday Paradox: Why 23 People Means a 50% Shared Birthday
Why 23 people give a 50% chance of two sharing a birthday — the counterintuitive math behind the birthday paradox, with worked examples and hash collisions.
#birthday paradox#probability#mathRead more - · Li Lei
The Arithmetic Sequence Formula, Worked Out: nth Term, Sum, and Common Difference
Find the nth term, the sum of the first n terms, and the common difference of any arithmetic sequence with worked examples and the formulas behind them.
#arithmetic sequence#math#sequencesRead more - · Li Lei
Annulus Area Made Simple: Find the Ring Area Between Two Circles
The area of an annulus is the outer circle minus the inner one, A = π(R² − r²). A practical guide for washers, pipes, tracks, and garden rings, with a worked example.
#geometry#calculator#mathRead more - · Li Lei
Degrees, Radians, Gradians and Turns: How to Convert Any Angle
A plain guide to angle units: degrees, radians, gradians and turns, the exact conversion factors, and which unit math, code and surveying each expect.
#math#angles#degreesRead more - · Lei Li
Designing a 24-Point Worksheet in 10 Minutes With a Solver
Picking 30 hands for a fourth-grade 24-point worksheet by hand takes 45 minutes and produces a mess. A browser solver sorts hands by solution count and difficulty, dropping the loop to 10 minutes. Here is the workflow.
#math#puzzle#educationRead more - · Lei Li
Why Some 24-Point Hands Have 28 Solutions and Others Have Just One
Solution density varies wildly across 24-point hands. One hand returns 28 distinct expressions; another returns one. Here is the combinatorics behind it, two worked hands, and what dense vs sparse hands mean for practice.
#math#puzzle#mental-arithmeticRead more - · Lei Li
When the 24-Point Solver Returns Multiple Answers, Pick This One
A 24-point hand can have one solution or eight. The solver shows them all in 50 ms — but a parent or teacher needs exactly one to put on the whiteboard. Three filters that pick the survivor.
#math#education#24-pointRead more - · Lei Li
The Fraction Test: Why a 24-Point Solver Beats You on Certain Hands
Some 24-point hands have no integer-only solution path. A solver finds them anyway. Here is which hands those are, why brains skip them, and how to train the gap closed.
#math#puzzle#educationRead more - · Lei Li
24-Point Solver: Every Way to Make 24, Found in 50 ms
The 24-point puzzle has a 7,680-branch search space and about 39 unsolvable hands. A browser solver walks the whole tree before you finish reading this sentence — here is what it is useful for, and what it is not.
#math#puzzle#educationRead more - · Lei Li
The 24-Point Solver Is a Better Coding-Interview Warm-up Than LeetCode Easy
Five minutes of 24-point hands before a coding interview wakes the same working-memory circuit that algorithm tracing uses — without burning a problem you might want to see again. Here is the routine, the data, and the three hands that stopped me cold last week.
#puzzle#interview-prep#mental-arithmeticRead more - · Lei Li
Why I Use the 24-Point Solver as a Family Game Referee, Not a Cheat Sheet
Five months of Sunday-night 24 games taught me the most useful job a 24-point solver does is not finding answers — it is settling disputes. Here is the workflow, the real hands, and the one verdict worth more than all the solutions combined.
#math#puzzle#educationRead more - · Lei Li
From 92 Seconds to 11: My 30-Day Drill Log With the 24-Point Solver
I logged 600 hands of the 24 game over 30 days with a browser solver as my answer key. Median solve time dropped from 92 seconds to 11. Here is the drill, the data, and the four mistakes that cost me the first two weeks.
#math#puzzle#mental-arithmeticRead more - · Lei Li
Four 24-Game Patterns That Cover Most Hands (and the One That Doesn't)
Six weeks of nightly 24-game practice taught me four patterns that crack the majority of hands inside ten seconds. Here are the templates, real examples, and the one hand-family where no pattern helps.
#math#puzzle#mental-arithmeticRead more
Developer & DevOps 175
- · Li Lei
Shell Quoting Mistakes That Break Deploy Scripts: Spaces, Dollars, Newlines, JSON, and SSH
Five quoting failures that keep breaking real deploy scripts — spaced filenames, $ expansion through SSH, JSON bodies in curl, newlines in variables — with actual broken output and the safe copy-paste fix for each.
#shell#bash#deploymentRead more -
How to Encode JSON Strings for APIs: curl, fetch, and the Characters That Break Payloads
A hands-on guide to encoding JSON strings correctly for REST API calls — which characters to escape, real curl and fetch examples, and how to fix the parser errors your server throws.
#json#api#encodingRead more - · Li Lei
DNS Cutover Checklist for Web App Deploys: TTL Prep, dig Checks, and Zero-Downtime Flips
A step-by-step DNS cutover checklist for moving a web app: when to drop TTLs, choosing between A, AAAA, CNAME and ALIAS, verifying with dig, and rolling back fast.
#dns#deployment#devopsRead more - · Lei Li
Base64 Encoding Explained for Developers: UTF-8 Bytes, Padding Rules, and the Decode Errors They Cause
How Base64 actually maps bytes to characters, why btoa() corrupts UTF-8 text, what 'Incorrect padding' really means in Python, and how to fix the four decode errors developers hit most.
#encoding#base64#utf-8Read more - · Lei Li
Converting Kubernetes Manifests and Helm values.yaml to JSON: A Practical CI/CD Workflow
When jq, JSONPath, or policy engines need JSON input, your Kubernetes YAML must be converted first. This guide covers real CI/CD examples, batch conversion patterns, and an honest comparison with yq.
#yaml#json#kubernetesRead more - · Li Lei
YAML vs JSON: Syntax Differences, When to Choose Each, and How to Convert
A developer's guide to the concrete syntax differences between YAML and JSON — where they bite you, when to pick each, and how to convert cleanly in both directions.
#yaml#json#configRead more - · Li Lei
XML to JSON Conversion: Patterns, Gotchas, and Best Practices for Developers
A deep dive into real-world XML to JSON conversion patterns: how to handle attributes, mixed content, repeated elements, and the array ambiguity that breaks most naive converters.
#xml#json#data conversionRead more - · Lei Li
URL Encoding vs Base64: How to Tell Them Apart and When to Use Each
A developer's guide to URL encoding and Base64 encoding — what each one does, how to recognize them on sight, real input/output examples, and a quick debugging checklist for HTTP requests.
#encoding#developer#webRead more -
Unicode Code Points Explained: U+ Notation, UTF-8, UTF-16, and Emoji Clusters for Developers
A practical developer guide to Unicode code points — how U+ notation works, how UTF-8 and UTF-16 encode the same characters differently, and why emoji clusters break your string length checks.
#unicode#utf-8#utf-16Read more - · Lei Li
JSON, YAML, and TOML Conversion Guide: What Changes, What Breaks, and Why
A practical guide to converting config files between JSON, YAML, and TOML — real before-and-after examples, the gotchas that silently break conversions, and which format to start with.
#json#yaml#tomlRead more -
JSON String Escaping Rules: What Your API Parser Rejects and Why
A debugging-first guide to JSON string escaping — which characters must be escaped per RFC 8259, how to read the error your parser throws, and real payload examples that show the fix.
#json#escaping#apiRead more -
CSV Deep Dive: Delimiter Detection, Type Inference Traps, and Null Value Conventions
Why semicolons, tabs, and pipes break comma-assuming parsers; how Excel silently destroys dates and phone numbers; and how null conventions vary across exporters — with real input/output examples.
#csv#data#parsingRead more - · Lei Li
Unicode Normalization in JavaScript: Why === Lies and How .normalize() Fixes It
NFC, NFD, NFKC, NFKD — four normalization forms that explain why JavaScript's strict equality fails on visually identical strings with accents and emoji. Practical code examples, emoji edge cases, and when to use each form.
#unicode#javascript#NFCRead more - · Li Lei
JSON vs YAML vs TOML: Pros, Cons, and When to Use Each
A structured breakdown of JSON, YAML, and TOML pros and cons with side-by-side syntax examples, parse speed numbers, and clear guidance on which config format to pick.
#json#yaml#tomlRead more -
HEX, RGB, and HSL in CSS: Which Format to Use and When
A practical breakdown of CSS color formats — HEX, RGB, HSL, and oklch — with real converter examples showing exactly what each format produces and when each one earns its place in your stylesheet.
#css#color#hexRead more -
JSON, YAML, and TOML Compared: Choosing the Right Config Format for Your Project
A practical comparison of JSON, YAML, and TOML for configuration and data files — syntax, readability, tooling support, and when to pick each one.
#json#yaml#tomlRead more -
JSON String Escaping: Special Characters, Unicode Escapes, and the Edge Cases That Bite Developers
A practical reference for JSON string escaping — which characters must be escaped, how Unicode escapes work, and the subtle bugs that trip up even experienced developers.
#json#escaping#unicodeRead more - · Li Lei
Regular Expressions Cheat Sheet: Email, URL, and Date Patterns Every Developer Reaches For
Three production-ready regex patterns — email, URL, and ISO date — with exact JavaScript examples, edge-case tables, and performance notes.
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Regex Cheat Sheet: 6 Essential Patterns Every Developer Should Bookmark (Email, URL, Phone, Date, IP, Slug)
Production-ready regex patterns for email, URL, phone, date, IP address, and URL slug validation — with real input/output examples and the edge cases each one catches.
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Python Regex Tutorial: re Module, Compiled Patterns, Named Groups, and Real-World Scraping
A practical Python regex guide covering the re module, compiled patterns, named groups, and real scraping examples — with benchmarks and copy-paste code.
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JavaScript Regular Expressions: Flags, Named Capture Groups, Lookahead, and String Replace
A practical guide to JavaScript RegExp — covering all 8 flags, named capture groups, lookahead/lookbehind assertions, and how .replace() works with capture group references.
#javascript#regex#named-capture-groupsRead more -
CSV Format Guide: Quoting Rules, Encoding Pitfalls, and Parser Edge Cases
A practical deep-dive into CSV quoting rules, BOM issues, line-ending differences, and the edge cases that break most parsers — with real input/output examples.
#csv#data#encodingRead more - · Lei Li
Why Your Search Breaks on é, ü, and ñ: A Practical Guide to Unicode Normalization Forms
NFC, NFD, NFKC, NFKD — four letters that explain why two strings that look identical fail a strict equality check. Here is what each form actually does, when to use it, and how to test your text before it reaches production.
#unicode#text-processing#developerRead more -
25 Regex Patterns Every Developer Should Know (Copy-Paste Snippets)
A practical guide to 25 real-world regex patterns for validation, extraction, and log parsing — with exact input/output examples you can run today.
#regex#developer-tools#programmingRead more - · Lei Li
JSON vs YAML vs TOML: Syntax Traps and Tooling Support Every Developer Should Know
A developer's field guide to JSON, YAML, and TOML configuration file formats — the surprising syntax gotchas, IDE and schema tooling gaps, and hard-won rules for picking the right format.
#json#yaml#tomlRead more - · Lei Li
JSON vs YAML vs TOML: Choosing the Right Config Format for Your Project
A practical guide to JSON vs YAML vs TOML for backend and frontend config files — real benchmarks, format examples, and a decision matrix to pick the right one fast.
#json#yaml#tomlRead more -
JSON.stringify Edge Cases That Will Catch You Off Guard: Circular References, BigInt, Unicode, and Undefined
A practical breakdown of the four JSON.stringify behaviors that trip up even experienced JavaScript developers — with real examples and fixes for each.
#javascript#json#debuggingRead more -
How to Sort Lines of Text Alphabetically, Numerically, and by Length: CLI, JavaScript, and Online
Three practical methods for sorting text lines — the Unix sort command, JavaScript Array.sort, and a browser-based tool — with real examples and benchmarks.
#text#developer-tools#cliRead more - · Lei Li
SHA-256 vs MD5 vs SHA-1: Which Hash Function to Use in 2026
A concrete decision guide to SHA-256, MD5, and SHA-1 in 2026 — covering the SHAttered attack, Git's hash transition, speed benchmarks, and exactly when each algorithm is still acceptable.
#security#cryptography#developerRead more -
CSS Filter Functions Explained: blur, brightness, contrast, hue-rotate, and drop-shadow with Real Examples
A practical guide to CSS filter functions — how blur, brightness, contrast, hue-rotate, and drop-shadow work, how to chain them, and the GPU performance numbers you need to know.
#css#filter#blurRead more -
CSS box-shadow Layering: Multi-Layer Effects, Performance Trade-offs, and Copy-Paste Code
How to layer CSS box-shadow declarations for depth, glow, and outline effects — with complete syntax reference, real browser-tested examples, and performance benchmarks.
#css#box-shadow#layeringRead more -
WCAG Color Contrast Requirements Explained: AA, AAA, and the Non-Text Rule Most Teams Miss
A complete map of WCAG 2.2 contrast success criteria — SC 1.4.3 (text), SC 1.4.6 (AAA), and SC 1.4.11 (non-text UI) — with real hex examples, the five legal exemptions, and how to fix every failure type.
#accessibility#wcag#color contrastRead more - · Li Lei
kubectl Cheatsheet: Essential Kubernetes Commands for Managing Pods, Deployments, and Services
A practical kubectl cheatsheet for developers who manage pods, deployments, and services every day — with real command output, rollout patterns, and time-saving flags.
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Dockerfile Best Practices: Multi-Stage Builds, Layer Caching, and Real Image Size Cuts
How to write Dockerfiles that build fast, ship small, and don't run as root — with real before/after examples and benchmark numbers.
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Docker Compose: A Practical Guide to Multi-Service Local Dev with Networking, Volumes, and Env Vars
Learn how to wire together multi-service apps in Docker Compose — networking between containers, named volumes for persistence, and safe environment variable patterns with real working examples.
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Docker Commands Cheatsheet: Real Examples for Everyday Container Workflows
A practical Docker commands cheatsheet covering the commands developers actually run every day — with real terminal examples, debugging tips, and Compose shortcuts.
#docker#devops#containersRead more - · Lei Li
MD5, SHA-256, and SHA-512 Compared: Choosing the Right Hash Function
A practical guide to MD5, SHA-256, and SHA-512: what each algorithm guarantees, where MD5 breaks down, when to use each one, and the one situation where none of them is the right answer.
#security#cryptography#developerRead more -
JSON vs YAML vs TOML: A Practical Config Format Comparison with Real Project Examples
A hands-on comparison of JSON, YAML, and TOML configuration formats — same config written three ways, parse speed differences, and clear guidance on when each format wins.
#json#yaml#tomlRead more - · Li Lei
YAML to JSON, and Back Again: A Practical Conversion Guide
How to convert YAML to JSON and JSON to YAML without losing data — why configs use YAML, why APIs want JSON, and the type-coercion traps that bite.
#yaml#json#converterRead more - · Li Lei
How to Format YAML: A YAML Formatter for Clean Indentation and Diffs
Format YAML with consistent spaces (not tabs), sort keys for stable diffs, and validate that it parses — straight from your browser, no upload.
#yaml#formatting#devopsRead more - · Li Lei
How to Convert XML to JSON Without Losing Attributes or Arrays
A practical guide to converting XML to JSON: how attributes, text nodes, and repeated elements map, the single-vs-array ambiguity, and why it stays local.
#xml#json#converterRead more - · Li Lei
How to Convert a URL List into JSON, Markdown, CSV, SQL IN, and TypeScript
Turn a plain list of URLs into a JSON array, Markdown link list, CSV, SQL IN clause, or TypeScript union in one step, for sitemaps, redirect tables, and link docs.
#urls#converter#jsonRead more - · Li Lei
Unicode Escape Explained: Text to \uXXXX and Back
A practical guide to Unicode escape sequences — how \uXXXX works, why emoji split into surrogate pairs, where to use them in JSON, JS, CSS, and HTML, with a full round-trip example.
#unicode#encoding#javascriptRead more - · Li Lei
TSV to JSON: Paste From Excel and Get an Array of Objects
Convert tab-separated values to JSON in your browser. Paste straight from Excel or Sheets, the header row becomes keys, and each row turns into one object.
#tsv#json#converterRead more - · Li Lei
Formatting TOML and Converting It to JSON Without the Guesswork
A practical guide to formatting TOML config, converting TOML to and from JSON, and why Cargo and pyproject picked TOML over YAML for tables and arrays.
#toml#json#yamlRead more - · Li Lei
Converting Line Endings: CRLF, LF, and the Invisible Carriage Return
Why CRLF and LF line endings break shell scripts, bloat git diffs, and confuse editors, plus how to normalize newlines locally and lock the rule in with .gitattributes.
#line endings#crlf#lfRead more - · Li Lei
Box Drawing With Unicode: Build Clean Text Boxes and Frames
Draw text boxes and frames with Unicode box-drawing characters for CLI output, ASCII diagrams, code comments and READMEs. Single vs double line styles explained.
#box-drawing#text-box#asciiRead more - · Li Lei
How to Embed an SVG as a Data URI in CSS and HTML
Inline a small SVG icon as a data URI in CSS or HTML, URL-encode it instead of base64 to save bytes, and drop one HTTP request per icon.
#svg#data-uri#cssRead more - · Li Lei
How to Escape a String for JSON, SQL, Shell, and Every Other Target
Escaping a string isn't one rule. JSON, JavaScript, HTML, CSV, SQL, and regex each guard different characters. Here's how to escape text safely for each.
#string-escape#json#sqlRead more - · Li Lei
How to Convert a Social Handle List: @ Usernames to CSV, JSON, and Markdown
Turn a pasted list of @ usernames into CSV, JSON, Markdown link lists, SQL IN, or a TypeScript union for influencer CRMs and mention tracking, all in your browser.
#social-media#influencer-marketing#data-cleanupRead more - · 李雷
Reverse Text the Right Way: Five Ways to Flip a String
A practical guide to reverse text by character, word, line, or letters-in-place, plus upside-down flips — with one input run through all four modes and the Unicode trap to avoid.
#reverse text#unicode#text toolsRead more - · Li Lei
How to Visualize Regex as a Railroad Diagram (and Actually Read It)
Use a regex visualizer to draw your pattern as a railroad diagram. See groups, alternation, and quantifiers as a path you can trace instead of dense syntax.
#regex#developer-tools#debuggingRead more - · 李雷
A Practical Guide to Regular Expressions: Classes, Groups, and Flags
Learn regular expressions the way you actually use them: character classes, quantifiers, groups, anchors, capture groups, flags, plus a worked email and phone matching example you can run live.
#regex#regular-expressions#javascriptRead more - · Li Lei
How to Extract Regex Matches From Text: Pull Every Date, Code, and Field at Once
A practical guide to extracting all regex matches from text at scale, reading capture groups, and why an extractor beats a tester for harvesting data.
#regex#text-processing#developer-toolsRead more - · Li Lei
Regex Escape: Make a String Match Literally Instead of as a Pattern
Why regex escape matters: backslash-escape special characters so .*+?()[] match literally. Worked example escaping an IP, plus matching user input and filenames safely.
#regex#regex escape#developer toolsRead more - · Li Lei
A Practical Regex Cheatsheet: Reading Regular Expressions Without Fear
Learn regex building blocks — character classes, quantifiers, anchors, groups, lookahead — plus greedy vs lazy and ready patterns for emails and dates.
#regex#regular expressions#developer toolsRead more - · Li Lei
Build Regex from Examples: Give Samples, Get a Pattern That Fits
Stop writing regex blind. Paste strings that should match and ones that shouldn't, infer a pattern, generalize it safely, then verify the edges before you ship.
#regex#developer-tools#text-processingRead more - · Li Lei
Turn a Query String to JSON: Parse ?a=1&b=2 Into an Object
Parse a URL query string into JSON, decode percent-encoding, fold repeated params into arrays, and debug broken links — with a worked ?name=tom&age=20 example.
#query string#json#urlRead more - · Li Lei
Converting a Java .properties File to JSON Without Losing a Key
A practical guide to turning Java and Spring .properties files into JSON: how dotted keys nest, how escaping works, and how to migrate config safely.
#java#properties#jsonRead more - · Li Lei
Power to Weight Ratio: Why a Lighter Car Beats a Stronger One
Power to weight ratio predicts acceleration and climbing better than raw horsepower. Learn W/kg and hp/ton, with a worked car example and cycling benchmarks.
#power-to-weight-ratio#cars#cyclingRead more - · Li Lei
Convert a Phone List to CSV, JSON, and SQL IN for Bulk Sends
Turn a pasted list of phone numbers into CSV, JSON arrays, SQL IN clauses, or TypeScript unions for SMS imports and CRM uploads, all in your browser.
#phone numbers#csv#jsonRead more - · Li Lei
The Nginx Config Directives I Actually Reach For: A Practical Nginx Cheat Sheet
A working Nginx cheat sheet covering server and location blocks, reverse proxy, redirects, gzip, TLS, static files, plus how to test and reload config safely.
#nginx#devops#reverse-proxyRead more - · 李雷
Mock Data the Smart Way: Generate Realistic Test Data in JSON, CSV, and SQL
Why tests and demos need fake data, how to generate names, emails, and addresses, export to JSON, CSV, or SQL, and keep it all running locally with reproducible seeds.
#mock data#test data#jsonRead more - · Li Lei
How to Normalize MAC Addresses Into One Canonical Form
Three notations, two cases, one device. Learn why network inventories and allowlists break until you normalize MAC addresses to a single canonical form.
#networking#mac-address#data-cleanupRead more - · Li Lei
How to Generate a MAC Address for Testing and Virtual Machines
A practical guide to generating MAC addresses for labs, VMs and DHCP tests: the 48-bit layout, the OUI vendor prefix, the locally-administered and unicast bits, and colon vs hyphen formats.
#networking#mac-address#virtualizationRead more - · Li Lei
How to Clean Logs Before You Paste Them: A Practical Log Cleaner Guide
Strip timestamps, ANSI color codes, and log levels, drop noise lines, and normalize logs for diffing or sharing — all processed locally in your browser.
#logs#debugging#devopsRead more - · Li Lei
How to Convert a List to JSON Array Without Hand-Typing Brackets
Turn a line-per-item list into a clean JSON array: quote each line, join with commas, wrap in brackets. Covers string vs number arrays, dedupe and trimming empties.
#json#converter#developerRead more - · Li Lei
How to Turn a List Into a Comma Separated String (and Back)
Join a column of lines into one comma separated string for SQL IN clauses, CSV cells, and config arrays — with quoting, trimming, and a reverse split.
#text#sql#csvRead more - · Li Lei
Reading chmod Like a Sentence: A Linux Permissions and chmod Calculator Guide
Convert Linux file permissions between symbolic rwxr-xr-x and octal 755, learn the read=4 write=2 execute=1 math, special bits, and why 777 is dangerous.
#linux#chmod#file-permissionsRead more - · Li Lei
The kubectl Cheat Sheet for Running and Debugging Kubernetes Workloads
A practical kubectl cheat sheet for running and debugging Kubernetes workloads: get, describe, logs, exec, apply, scale, rollout, and context switching.
#kubectl#kubernetes#devopsRead more - · Li Lei
How to Test a JSONPath Query Without Writing a Throwaway Script
A practical guide to testing JSONPath queries — the $ root, [*] array iteration, .. recursive descent, filters, and debugging why an API response returns nothing.
#jsonpath#json#apiRead more - · Li Lei
JSONL to JSON: Convert JSON Lines (NDJSON) to a JSON Array and Back
How JSON Lines (NDJSON) works, why one object per line wins for logs, streaming, and LLM datasets, and how to wrap JSONL into a JSON array or unwrap it.
#jsonl#json-lines#ndjsonRead more - · Li Lei
JSON to YAML, and Back Again: A Practical Guide for Config Files
Convert JSON to YAML and back without losing types or readability. Indentation, quoting gotchas, why YAML wins for configs, and keeping secrets local.
#json#yaml#configRead more - · Li Lei
JSON to XML: Turning Keys Into Tags Without Breaking SOAP
A practical guide to converting JSON to XML — how keys become tags, arrays repeat elements, the single-root rule, attributes vs children, and escaping.
#json#xml#converterRead more - · Li Lei
From JSON to TypeScript Interface: Inferring Types You Can Trust
Turn a JSON sample into clean TypeScript interfaces. How type inference works, when fields become optional, how nested objects and arrays are typed, and how to type API responses.
#typescript#json#type-inferenceRead more - · Li Lei
JSON to TSV: The Clean Way to Paste Records Into a Spreadsheet
Convert a JSON array of objects to TSV so it pastes cleanly into Excel and Google Sheets. Why tabs beat commas, how keys become columns, and missing fields.
#json#tsv#spreadsheetRead more - · Li Lei
Converting JSON to TOML: Tables, Key-Values, and Cleaner Config
A practical guide to converting JSON to TOML by hand and with a tool: how nested objects become tables, how arrays of tables work, and when TOML beats YAML or JSON for config.
#json#toml#configRead more - · Li Lei
JSON to Swift Codable: Generate Structs, Optionals, and CodingKeys
Turn any JSON payload into Swift Codable structs. How type inference picks Int vs Double, when fields become Optional, and how CodingKeys maps snake_case keys.
#swift#json#codableRead more - · Li Lei
Turning a JSON Array Into SQL INSERT Statements: A Practical JSON to SQL Guide
How to convert a JSON array into clean SQL INSERT statements: keys become columns, values become VALUES, single quotes get escaped, ready for seeding and migrations.
#json#sql#databaseRead more - · Li Lei
JSON to Scala Case Classes: A Practical Field Guide
Turn JSON into Scala case classes with typed fields, nested child classes, Option for nullable keys, and decoders that work with circe and play-json.
#scala#json#case-classRead more - · Li Lei
From JSON to Rust Structs in One Paste: A serde Field Guide
Turn any JSON payload into Rust structs with serde Deserialize derives, Option for nullable fields, Vec for arrays, and nested sub-structs — no hand-typing.
#rust#serde#jsonRead more - · Li Lei
JSON to Ruby Hash: Symbol Keys, Rocket Arrows, and Rails Fixtures
Turn API JSON into an idiomatic Ruby Hash literal with symbol keys, => rocket syntax, or string keys. Worked examples for Rails fixtures and nested structures.
#ruby#json#railsRead more - · Li Lei
JSON to Query String: How to Serialize an Object into URL Params
Turn a JSON object into a clean URL query string. Learn how keys and values get encoded, how nested objects and arrays flatten, and how to build API URLs.
#json#query-string#url-encodingRead more - · Li Lei
JSON to Python Dataclass: Type Hints, Optional Fields, and Nested Classes Without the Boilerplate
Convert JSON to Python dataclass models with real type hints, Optional inference, and nested classes. A practical walkthrough plus dataclass vs Pydantic.
#python#dataclass#pydanticRead more - · Li Lei
From JSON to Pydantic Models: Runtime Validation You Can Trust
Turn any JSON payload into typed Pydantic BaseModel classes for FastAPI request bodies, nested models, and runtime validation that catches bad data.
#pydantic#python#fastapiRead more - · Li Lei
JSON to Protobuf: Generate a .proto Schema From Any Payload
Turn a JSON API response into a proto3 message: field numbers, scalar type mapping, repeated arrays, nested messages, and why protobuf is smaller and faster.
#protobuf#grpc#jsonRead more - · Li Lei
Converting JSON to a PHP Array Without a json_decode Round-Trip
How to turn JSON into a clean PHP array literal: objects become => associative arrays, indexed arrays, nested structures, and Laravel or WordPress config files.
#php#json#laravelRead more - · Li Lei
JSON to NDJSON: Convert a JSON Array to JSON Lines (and Back)
Turn a JSON array into NDJSON (JSON Lines) with one object per line for logs, streaming, Elasticsearch bulk loads, and ML datasets, then convert back.
#json#ndjson#jsonlRead more - · Li Lei
From JSON to Mongoose Schema: A Field by Field Conversion Guide
Turn a real JSON document into a typed mongoose.Schema. See how each JSON type maps to a SchemaType, how nested objects and arrays convert, and how to skip the boilerplate.
#mongoose#mongodb#nodejsRead more - · Li Lei
How to Convert a JSON to Markdown Table for READMEs and Issues
Turn a JSON array of objects into a clean Markdown table where keys become headers. Worked example, alignment separators, pipe escaping, and nested fields.
#json#markdown#developer-toolsRead more - · Li Lei
JSON to Kotlin Data Classes: A Practical Guide for Android Developers
Turn any JSON payload into clean Kotlin data classes — nullable types, nested classes, and @Serializable, Gson, or Moshi annotations done right.
#kotlin#android#jsonRead more - · Li Lei
JSON to Go Struct: Generate Typed Structs With json Tags From Any Payload
Turn any JSON payload into Go structs with json tags, exported fields, type inference, nested sub-structs, and slices — then decode it cleanly with encoding/json.
#go#golang#jsonRead more - · Li Lei
JSON to Dart Classes for Flutter: fromJson, toJson, and Null Safety Without the Boilerplate
Turn any JSON payload into Flutter-ready Dart model classes with fromJson factories, toJson, null-safe nullable types, and nested objects handled for you.
#flutter#dart#jsonRead more - · Li Lei
Generating JSON to C# Classes the Fast Way: Type Inference, Nullables, and JsonProperty Attributes
A practical guide to turning a JSON sample into clean C# classes — PascalCase properties, int vs long vs double inference, nullable handling, and JSON attributes.
#csharp#dotnet#jsonRead more - · Li Lei
How to Sort JSON Keys Alphabetically for Clean, Stable Diffs
Sort JSON keys alphabetically to kill noisy git diffs. Learn recursive key sorting, why deterministic order stabilizes snapshots, and a worked example.
#json#git#configRead more - · Li Lei
How to Infer a JSON Schema From Sample JSON
Turn real JSON payloads into a JSON Schema with inferred types, properties, and required fields. A practical guide to API contracts, validation, and nested data.
#json schema#json#apiRead more - · Li Lei
From a JSON Sample to a Typed JSON Schema in Five Seconds
Turn one real JSON object into a typed JSON Schema. See how inference assigns types, marks required fields, handles enums, and validates API payloads and configs.
#json-schema#json#api-validationRead more - · Li Lei
How to Minify JSON: Strip Whitespace Without Touching Your Data
Learn how to minify JSON safely: what whitespace gets removed, why smaller payloads help APIs and configs, and when minified beats pretty-printed.
#json#minify#developer-toolsRead more - · Li Lei
JSON Merge Done Right: Deep Merge, Array Strategies, and Config Layering
How to merge two or more JSON objects: deep merge vs shallow merge, why the later object wins on conflicts, array strategies, and clean config layering.
#json#deep merge#configRead more - · Li Lei
JSON Lines (JSONL) Explained: Format, Validate, and Find the Bad Line
A practical guide to JSON Lines (JSONL/NDJSON): why it beats a JSON array for logs and streaming, how per-line validation finds the one bad record fast.
#json#jsonl#ndjsonRead more - · 李雷
JSON Formatter Guide: Validate, Pretty-Print, and Minify Without the Headaches
A practical guide to using a JSON formatter to validate syntax, locate trailing-comma errors by line and column, choose pretty vs minified output, and keep data private.
#json#developer-tools#debuggingRead more - · Li Lei
How to Flatten JSON: Nested Objects to Dot-Path Keys (and Back)
A practical guide to flattening nested JSON into single-level dot-path keys for CSV export, env vars, and diffing — plus how to unflatten it cleanly.
#json#data-conversion#developer-toolsRead more - · Li Lei
How to Compare JSON: Find Added, Removed, and Changed Keys with a JSON Diff
A practical guide to comparing two JSON objects by key path so you spot real added, removed, and changed values instead of fake whitespace and key-order noise.
#json#debugging#apiRead more - · Li Lei
From JS Object to JSON: Quote the Keys, Drop the Trailing Comma, Get Strict JSON
Turn a JavaScript object literal into valid JSON: quote bare keys, swap single quotes for double, strip trailing commas and comments. With a worked example.
#json#javascript#developer-toolsRead more - · Li Lei
How to Minify JavaScript: A Practical Guide to the JS Minifier
Minify JavaScript to cut download size and load time. How a JS minifier strips whitespace and comments, plus minify vs uglify vs obfuscate explained.
#javascript#minify#performanceRead more - · Li Lei
Convert a Date List: Turn ISO Dates into SQL, JSON, CSV and TypeScript
Paste a column of ISO dates and convert the list into a SQL IN clause, JSON array, CSV, Markdown, or TypeScript union for queries, fixtures, and seed data.
#iso dates#sql#jsonRead more - · Li Lei
How to Normalize IPv6 Addresses to One Canonical Form (RFC 5952)
One IPv6 host can be written a dozen ways. Learn the RFC 5952 rules and use a local tool to normalize IPv6 addresses into a single canonical spelling.
#ipv6#rfc 5952#networkingRead more - · Li Lei
Convert an IPv6 List to SQL IN, JSON, CSV, and TypeScript in One Step
Turn a column of IPv6 addresses into a SQL IN clause, JSON array, CSV, or TypeScript union for log queries, configs, and allowlists without hand-quoting.
#ipv6#sql#jsonRead more - · Li Lei
How to Deduplicate IPv6 Addresses When One Host Has Many Spellings
IPv6 hosts wear many spellings, so a plain dedup keeps copies of the same address. Here is how to deduplicate IPv6 addresses correctly, with worked examples.
#ipv6#deduplication#networkingRead more - · Li Lei
How to Validate IPv4 Addresses From a Pasted IP List
Validate IPv4 addresses from a pasted list, catch out-of-range octets and malformed rows, and export a clean CSV or JSON allowlist your team can trust.
#ipv4#networking#validationRead more - · Li Lei
Convert an IPv4 Address List into SQL IN, JSON, CSV, and TypeScript Union
Turn a plain list of IPv4 addresses into a SQL IN clause, JSON array, CSV, or TypeScript union for log queries, allowlists, and firewall configs.
#ipv4#sql#log-analysisRead more - · Li Lei
How to Extract IP Addresses From Logs and Messy Text
A practical guide to pulling every valid IPv4 address out of access logs, configs, and pasted text, then deduping the list so you see the unique IPs hitting your server.
#ipv4#logs#networkingRead more - · Li Lei
INI to JSON: Turning Sections, Keys and Values into Clean Objects
A practical guide to converting INI config to JSON: how sections become nested objects, how key=value lines map to properties, type coercion, and migrating legacy config.
#ini#json#configRead more - · Li Lei
Tidying INI Config Files: A Practical Guide to the INI Formatter
How to clean up INI config files with section grouping, aligned key=value pairs, alphabetical sorting, and preserved comments, plus where INI still shows up.
#ini#config#formattingRead more - · Li Lei
Convert an HTTP Header List into JSON, CSV, and TypeScript in One Step
Turn a pasted list of HTTP headers into JSON, CSV, Markdown, SQL IN, or a TypeScript union for API clients and request configs, all parsed locally in your browser.
#http-headers#api#developer-toolsRead more - · Li Lei
How to Convert an HTML Table to JSON Without Writing a Scraper
Turn any HTML <table> into clean JSON: th cells become keys, each tr becomes an object, tags get stripped, and everything stays in your browser.
#html#json#scrapingRead more - · 李雷
How to Minify HTML: Strip Comments, Collapse Whitespace, Save 40-60% of Bytes
A practical guide to HTML minify: what to strip, how comments and whitespace inflate your markup, inline vs external assets, and the real page-speed payoff of smaller HTML.
#html#performance#web-developmentRead more - · Li Lei
gron Makes JSON Greppable: Flatten Deep JSON Into Searchable Assignment Lines
How gron rewrites JSON as one path-assignment per line so grep can find any deep value, how ungron rebuilds the JSON, and why it speeds up API debugging.
#json#gron#grepRead more - · Li Lei
The Go Idioms You Actually Reach For: A Golang Cheat Sheet
A practical Go cheat sheet for the idioms you type daily — structs, slices, maps, goroutines, channels, defer, and the if err != nil pattern, with real snippets.
#go#golang#cheatsheetRead more - · Li Lei
Glob Patterns Explained: Test * ? ** [] {} Against Real Paths
A practical guide to glob patterns — what * ? ** [] {} actually match, how they differ from regex, and how to test src/**/*.ts against real file paths.
#glob#gitignore#regexRead more - · Li Lei
How to Build a .gitignore That Actually Keeps node_modules and Secrets Out of Git
A practical guide to writing a .gitignore from language, framework, and OS templates, with glob patterns explained and a worked Node example you can copy.
#git#gitignore#developer-toolsRead more - · Li Lei
The Git Commands You Actually Reach For Daily: A Working Git Cheat Sheet
A practical guide to the Git commands you type every day, grouped by workflow, plus the few that rescue you in a panic: reset, revert, stash, reflog.
#git#git commands#version controlRead more - · Li Lei
How to Find and Replace Text in Bulk Without Fighting Your Editor
A practical guide to bulk find and replace: case-sensitive and whole-word options, regex with $1 capture groups, cleaning pasted text, all in your browser.
#find and replace#regex#text editingRead more - · Li Lei
How a FIGlet ASCII Banner Turns a Word Into Big Block Letters
A practical look at FIGlet ASCII banners: how a figlet font maps each letter to multi-line block art, where banners earn their keep, and how to pick a font.
#ascii#figlet#cliRead more - · Li Lei
How to Normalize Environment Variables and Clean Up a Messy .env File
Normalize environment variables to UPPER_SNAKE_CASE, trim values, strip surrounding quotes, and dedupe a messy .env so your config never reads the wrong key.
#environment-variables#dotenv#configurationRead more - · Li Lei
How to Validate Environment Variables and Clean a .env File in Your Browser
Validate environment variables and .env entries against the POSIX naming rule, catch illegal keys, and export a clean CSV or JSON report locally.
#environment variables#dotenv#devopsRead more - · Li Lei
Convert an Env Var List to JSON, TypeScript Union, CSV, or SQL IN
Turn a plain list of environment variable names into a JSON array, TypeScript union, CSV, Markdown, SQL IN, or one-per-line output for typed config and docs.
#environment variables#typescript#configRead more - · Li Lei
How to Extract Environment Variables from Code, Scripts, and Configs
Pull every env var reference out of your code and scripts in one pass, dedupe the names, and turn the list into a complete .env.example. Runs locally.
#environment variables#dotenv#devopsRead more - · Li Lei
How to Deduplicate Environment Variables in a Merged .env File
A duplicate key in a merged .env is a real config bug, not cosmetic. Here is how to find repeated environment variables and keep one clean copy.
#environment-variables#dotenv#devopsRead more - · Li Lei
How to Convert a .env File to JSON Without Leaking Secrets
A practical guide to turning a .env file into JSON: how KEY=value lines parse, why comments and blank lines drop, and how to feed config into JSON tools locally.
#env to json#dotenv#environment variablesRead more - · Li Lei
Secret Scanner Basics: How to Find Leaked Secrets in .env Files and Diffs
How a secret scanner finds leaked API keys, tokens, and private keys by matching known prefixes and high-entropy strings, with everything scanned locally.
#security#secrets#devopsRead more - · 李雷
Email Validator: Why Valid Syntax Doesn't Mean a Real Inbox
A practical guide to using an email validator — RFC 5321 syntax rules, why one regex can't reliably validate email, spotting common typos, and deduping bulk lists.
#email-validation#rfc-5321#data-cleaningRead more - · Li Lei
Convert an Email List into CSV, JSON, SQL IN, and TypeScript Union Output
Turn a plain list of email addresses into CSV, a JSON array, a SQL IN clause, a TypeScript union, or Markdown so you can paste them straight into a query, script, or doc.
#email#converter#sqlRead more - · Li Lei
How to Extract Email Addresses From Any Block of Text
A practical guide to pulling every email address out of logs, exports, and copied pages with regex, then deduping and cleaning the list locally.
#email#regex#data-cleaningRead more - · Li Lei
The Elasticsearch REST API: A Practical ES Cheat Sheet
A working Elasticsearch cheat sheet for the REST API — index and get docs, the query DSL match vs term, bool queries, aggregations, mappings, and cat APIs.
#elasticsearch#search#rest-apiRead more - · Li Lei
How to Validate a .env File: A Practical dotenv Validator Walkthrough
Validate a .env file the right way: catch spaces around the equals sign, unquoted values, duplicate keys, and missing required variables before they break a deploy.
#dotenv#env-file#configurationRead more - · Li Lei
How to Convert a DOI List into JSON, CSV, Markdown, SQL IN, and TypeScript Union
Turn a flat list of DOIs into a JSON array, CSV column, Markdown link list, SQL IN clause, or TypeScript union for bibliographies and reference datasets.
#doi#bibliography#reference-dataRead more - · Li Lei
The Docker Commands You Actually Type: A Working Docker Cheat Sheet
A practical Docker cheat sheet for everyday container work — run, build, ps, logs, exec, compose, prune, plus how to debug a container that keeps exiting.
#docker#containers#devopsRead more - · Li Lei
DNS Records Explained: A, AAAA, CNAME, MX, TXT and the Rest of the Zone
A practical guide to DNS record types — what A, AAAA, CNAME, MX, TXT, NS, SOA and SRV do, how to read a zone, plus TTL, propagation and common setups.
#dns#networking#devopsRead more - · 李雷
CSV to JSON: The Edge Cases That Break Naive Parsers (And How to Get It Right)
A practical guide to converting CSV to JSON correctly — quoted commas, embedded newlines, escaped quotes, type inference, and flat vs nested shapes, with real input and output.
#csv#json#data-conversionRead more - · Li Lei
The CSS transform Property: A Practical Guide to translate, rotate, scale, and skew
A hands-on guide to the CSS transform property — translate, rotate, scale, skew, transform-origin, and why transforms animate smoothly on the GPU.
#css#transform#animationRead more - · 李雷
How to Minify CSS: What Gets Stripped and How Much You Save
A practical guide to minifying CSS — how comment stripping, whitespace collapse, and color shortening shave 30-60% off your stylesheet, with a real before/after example.
#css#performance#web-devRead more - · 李雷
A Practical Guide to CSS Keyframes and Animation Properties
Learn how @keyframes works, what each CSS animation property does, how to build fade, slide, and bounce effects, and why animating transform and opacity keeps motion smooth.
#css#animation#keyframesRead more - · Li Lei
The CSS filter Property, Demystified: blur, brightness, contrast, grayscale, and drop-shadow
A practical guide to the CSS filter property: how blur, brightness, contrast, grayscale, and drop-shadow work, how filters stack, and how to keep them fast.
#css#filter#frontendRead more - · Li Lei
How to Read and Write a Crontab Cron Expression Without Guessing
Learn the five cron fields, common scheduling patterns, the @daily shortcuts, and the timezone and overlap pitfalls that quietly break scheduled jobs.
#cron#crontab#linuxRead more - · 李雷
How to Read a Cron Expression: Decode the Five Fields, the Stars, and the Slashes
A practical guide to reading any cron expression. Learn the five fields, what * / , - mean, the day-of-week 0-vs-7 trap, and how to preview the next runs before you ship a broken schedule.
#cron#crontab#schedulingRead more - · Li Lei
Convert a Card Number List Into JSON, SQL IN, or a TypeScript Union for QA Fixtures
Turn a list of test card-shaped numbers into CSV, JSON, SQL IN, or TypeScript union output for QA fixtures. Values stay masked in the output. Runs fully in your browser.
#test data#qa fixtures#credit cardRead more - · 李雷
Conventional Commit Format: feat, fix, and Why It Powers Auto-Changelogs
A practical guide to the Conventional Commit format: how feat, fix, chore, scope, and breaking changes drive automated changelogs and semantic version bumps.
#conventional commits#git#changelogRead more - · 李雷
Common Ports Explained: A Working Reference for Port Numbers
A practical guide to common ports and port numbers: 22, 80, 443, 3306, 5432 and more, plus well-known vs registered ranges and how to troubleshoot a port that won't connect.
#networking#ports#devopsRead more - · Li Lei
Cloudflare DNS Records Explained: Proxy, TTL, and CNAME Flattening
A practical guide to Cloudflare DNS records (A, AAAA, CNAME, MX, TXT), the orange-cloud proxy, TTL choices, CNAME flattening at the root, and email setup.
#cloudflare#dns#emailRead more - · Li Lei
chmod Calculator Guide: Reading Unix File Permissions in Octal and Symbolic Notation
A plain-English guide to Unix file permissions and chmod: how octal and symbolic notation work, what 644 and 755 mean, and why 777 is a security risk.
#linux#file-permissions#chmodRead more - · Li Lei
The Cache-Control Header Explained: A Practical Guide to HTTP Caching
A hands-on guide to the Cache-Control header and its directives — max-age, no-cache, no-store, public, private, immutable — and how to cache static assets safely.
#http#caching#performanceRead more - · Li Lei
Bash Commands That Actually Matter: A Practical Bash Cheat Sheet
A working guide to the Bash you write in scripts and the terminal — variables, conditionals, loops, pipes, parameter expansion, and the quoting and set -euo pipefail gotchas.
#bash#shell scripting#cheat sheetRead more - · Li Lei
The AWS S3 Cheat Sheet I Actually Use: cp, sync, presign, and Bucket Policies
A practical AWS S3 cheat sheet for the CLI commands you run daily — cp, sync, ls, rb, presigned URLs, storage classes, bucket policies vs ACLs, and static hosting.
#aws#s3#cliRead more - · Li Lei
AWS IAM Cheat Sheet: Policies, Roles, and the JSON That Decides Access
A practical AWS IAM cheat sheet covering users, groups, roles, policy JSON (Effect/Action/Resource/Condition), least privilege, and a read-only S3 example.
#aws#iam#securityRead more - · Li Lei
AWS CLI Cheat Sheet: The Commands You Actually Run on S3, EC2, and IAM
A practical AWS CLI cheat sheet for S3, EC2, and IAM — profiles, regions, the --query JMESPath flag, output formats, and a copy-ready quick reference.
#aws-cli#devops#cheatsheetRead more - · Li Lei
The ASCII Table Explained: Code Points 0–127, Bases, and Why 'A' Is 65
How the ASCII table maps 128 code points to characters, why 'A' is 65 and 'a' is 97, how to read decimal/hex/binary columns, and ASCII's role under UTF-8.
#ascii#encoding#textRead more - · Li Lei
API Rate Limiting Explained: Reading API Rate Limits, 429s, and Backoff
How API rate limiting works: token bucket vs sliding window, the standard headers, what 429 and Retry-After mean, and how clients should back off safely.
#api#rate-limiting#backoffRead more - · Li Lei
Apache Cheat Sheet: httpd Config, VirtualHost, mod_rewrite, and apachectl
A practical Apache cheat sheet covering VirtualHost, DocumentRoot, mod_rewrite, .htaccess, enabling modules, apachectl, and reverse proxying.
#apache#httpd#virtualhostRead more - · Lei Li
Base64 Encoding Explained for Developers: When to Use It and Common Mistakes
How Base64 maps bytes to text, a measured look at its 33% size overhead, when it is the right choice, and five mistakes that cause real production bugs.
#encoding#developer#base64Read more - · Lei Li
How to Compute an EAN-13, UPC-A, or EAN-8 Check Digit — and Catch Typos Before the Label Prints
A practical guide to the GS1 mod-10 check digit algorithm. Includes a worked example, common mistakes, and the fastest way to verify a barcode before it reaches your label printer or product feed.
#barcode#ean#upcRead more - · Lei Li
JWT Structure Explained: Header, Payload, Signature, and How to Decode Them Safely
A practical breakdown of the three parts inside every JWT token — what each section contains, how the signature ties them together, and how to decode claims without accidentally trusting an unverified token.
#jwt#authentication#developerRead more - · Lei Li
Base64 vs Base64URL: The Three Characters That Break JWTs and API Tokens
A practical breakdown of the two Base64 variants, real encoding examples showing exactly where they differ, and the four bugs developers hit most often when mixing them up.
#encoding#jwt#developerRead more - · Lei Li
Regex Escaping Cheat Sheet for JavaScript, Python, JSON, and URLs
A practical regex escaping cheat sheet for moving literal text through JavaScript, Python, JSON, and URL query strings without losing backslashes.
#regex#javascript#pythonRead more - · Lei Li
BCD and Hex Conversion in Practice: Why BCD Still Survives
A practical guide to BCD and hex conversion, with real outputs, instrumentation and finance examples, a large-number precision boundary, and a local Toolora benchmark.
#encoding#developer#financeRead more - · Lei Li
Base64 vs URL Encoding: When to Use Each and Common Mistakes
A practical guide to choosing Base64 or URL encoding for API parameters, redirects, data URLs, files, and tokens, with real input/output examples and a reproducible size benchmark.
#encoding#developer#webRead more - · Lei Li
A Complete Guide to Base64 Encoding: How It Works, Padding, URL-Safe Variants, and Common Mistakes
Understand Base64 encoding at the byte level, including padding, Base64url, hex conversion, image data URIs, and the mistakes that break tokens and files.
#encoding#base64#developerRead more - · Lei Li
Base32 vs Base58 vs Base85: How to Choose a Binary-to-Text Encoding
A practical comparison of Base32, Base58, and Base85 alphabets, real output examples, and measured size overhead for tokens, QR codes, source embeds, and binary streams.
#encoding#developer#benchmarkRead more - · Lei Li
awk + sed Cheatsheet: Wrangling CSV Columns Without Loading Pandas
Sum a column, group by a key, swap fields, and fix delimiters in a CSV using awk and sed one-liners — with real input, real output, and a timing comparison against pandas.
#awk#sed#csvRead more - · Lei Li
Practical Text Banners for READMEs and Terminals
A practical guide to making ASCII art banners that work in READMEs, terminal output, docs, and launch screens, with real input and output examples.
#ascii#developer#readmeRead more - · Lei Li
JPG vs WebP vs AVIF: Best Image Format in 2026 (Real Benchmarks)
I ran the same 47 images through JPG, WebP, and AVIF at matched quality. AVIF wins on size by 50%, WebP wins on browser support, JPG still wins one specific case. Here's the breakdown.
#image#performance#tutorialRead more - · Lei Li
Format JSON Online: 5 Scenarios You Hit Every Week
A browser-only JSON formatter saves a surprising amount of time. Here are five concrete scenarios where I reach for one instead of opening an IDE, plus when to use beautify vs minify.
#json#developer#tutorialRead more - · Lei Li
Cron Expression Syntax Cheat Sheet: 15 Real Crontab Examples
The five fields of a cron expression, 15 crontab examples I actually use in production, and the three gotchas (DST, timezone, missing newline) that have bitten me at 3 am.
#cron#devops#tutorialRead more - · Lei Li
chmod 755 vs 644 Explained: Linux File Permissions Without the Mystery
Why 755 for directories and executables, 644 for everything else, and the setuid trap that bit me in production. Linux file permissions explained with the octal-to-symbolic map that finally made it click.
#linux#devops#tutorialRead more - · Lei Li
30 Browser Tools Every Developer Should Bookmark
The 30 zero-signup, fully local browser tools I open daily — grouped by JSON, cheatsheets, crypto, DevOps, text, and color.
#roundup#developer#toolsRead more
Design & Media 107
- · 李雷
LCH and OKLCH in CSS: Browser Support, Migration from Hex/RGB, and When to Use Each
A practical guide to lch() and oklch() in CSS — the difference between them, current browser support figures, and step-by-step migration patterns using @supports fallbacks.
#oklch#lch#cssRead more -
OKLCH Color in CSS: Complete Guide with Practical Examples for 2026
A hands-on guide to OKLCH color in CSS — syntax, real input/output examples, palette generation, and how to wire OKLCH into a practical token system for 2026 projects.
#css#color#oklchRead more -
HTML Entities vs. Unicode Escape Sequences: A Web Developer's Decision Guide
Named, decimal, hex, \uXXXX, \u{XXXXX}, CSS \XXXX — six ways to write one character. Learn exactly which form belongs in HTML, JavaScript, CSS, and URLs, with real examples that show where each breaks down.
#character-encoding#html-entities#unicodeRead more -
HSL vs OKLCH vs RGB: Which CSS Color Format to Use and When
A practical decision guide for choosing between HSL, OKLCH, and RGB in CSS — with real gradient examples, dark-mode token patterns, and a browser support breakdown.
#css#color#oklchRead more -
CSS Gradient Generator Guide: Hard Stops, Stripes, and Repeating Patterns for Linear, Radial, and Conic Gradients
A practical guide to hard-stop CSS gradients — with copy-paste code snippets for diagonal stripes, polka-dot backgrounds, checkerboards, and pie-chart segments using linear, radial, and conic gradients.
#css#gradients#web-designRead more -
CSS Custom Property Design Tokens: Naming Conventions, Structure, and Dark Mode
A practical guide to structuring CSS design tokens with custom properties — covering two-layer naming, file organization, and dark-mode patterns that work without JavaScript.
#css#design-tokens#dark-modeRead more -
Color Palette Theory for Web Developers: Calculating Complementary, Triadic, and Analogous Schemes in HSL
How to derive complementary, triadic, and analogous color schemes programmatically using HSL — with real CSS custom property examples, hex values, and WCAG contrast checks.
#color#css#web-developmentRead more -
WCAG Color Contrast Explained: AA vs AAA — 12 Common Color Pairs Tested
A plain-English guide to WCAG 2.2 color contrast ratios: what AA and AAA actually require, how the math works, and whether the 12 most popular UI color pairs survive the test.
#accessibility#wcag#colorRead more -
WCAG 2.1 AA vs APCA Contrast: What the New Algorithm Actually Measures
WCAG 2.1 AA and APCA measure color contrast differently. Learn how each algorithm works, where WCAG's ratio falls short, and how APCA's Lc values change your accessible color choices.
#accessibility#color#wcagRead more -
OKLCH in CSS: Why Gradients Go Muddy in HSL and How OKLCH Fixes It
HSL gradients between complementary colors collapse into an ugly grey mush. OKLCH interpolates through vivid intermediate hues instead. Here's the geometry, the CSS, and the perceptual science behind why.
#css#color#oklchRead more - · Lei Li
OKLCH in CSS: Perceptual Uniformity, P3 Wide-Gamut Colors, and What Every Browser Supports Now
A practical guide to the OKLCH color space in CSS — how perceptual uniformity makes palette building predictable, how P3 wide-gamut expands what you can show on modern screens, and exactly which browsers ship full support today.
#css#color#designRead more -
HSL vs HSV vs HWB: Which Color Model Actually Belongs in Your CSS and Design Workflow
A practical breakdown of HSL, HSV, and HWB — how each model works, where the numbers come from, and which one to reach for in CSS, Figma, or code.
#color#css#designRead more -
HEX vs RGB vs HSL: Which CSS Color Format Should You Use and When
A practical breakdown of HEX, RGB, and HSL color formats — with real code examples, browser support data, and clear rules for picking the right one in every situation.
#css#color#web-developmentRead more -
CSS Custom Properties for Dark Mode: Building a Scalable Color System
Learn how to architect a dark mode color system using CSS custom properties — with a three-layer token model, real code examples, and contrast-testing workflow.
#css#dark-mode#design-tokensRead more -
Color Palette Theory for UI: Complementary, Analogous, and Triadic Schemes Explained
A practical guide to applying complementary, analogous, and triadic color schemes in UI design — with real hex examples, contrast ratios, and tool workflows.
#color#ui-design#accessibilityRead more - · Li Lei
WCAG Color Contrast Ratios: A Practical Guide Beyond AA Compliance
AA compliance passes the audit but often fails real users. This guide explains what the contrast ratio formula actually measures, where AA falls short, and how to build a test workflow that catches failures automated tools miss.
#accessibility#wcag#color contrastRead more -
RTL Text in Web Development: CSS Logical Properties and the Bidi Algorithm for Arabic, Hebrew, and Persian
A practical guide to building right-to-left layouts with CSS logical properties, the Unicode Bidirectional Algorithm, and bidi control characters — covering Arabic, Hebrew, and Persian.
#rtl#css#unicodeRead more - · 李雷
Harmonic Ratios for Web Typography: Picking the Right Modular Type Scale
A practical guide to choosing between Perfect Fourth, Major Third, and Golden Ratio type scales for web — with real computed values, readability benchmarks, and CSS export examples.
#typography#css#design-systemsRead more -
Hex Color Codes Explained: RGB to Hex Conversion, CSS Formats, and When HSL Wins
A practical breakdown of hex color codes — how the RGB-to-hex conversion works, when to use hex vs. HSL vs. RGB in CSS, and which format fits each workflow.
#css#color#web-designRead more -
CSS Custom Properties for Design Tokens: Naming Conventions, Color Scales, and Team Patterns That Actually Work
A practical guide to structuring CSS custom properties as design tokens — covering naming systems, color scale generation, and patterns teams use to stay consistent at scale.
#css#design-tokens#custom-propertiesRead more -
CSS Color Functions in 2026: oklch, color-mix(), and Relative Colors Explained with Examples
A practical guide to oklch, color-mix(), and relative color syntax — the three CSS Color 4 features that change how you build palettes, tokens, and theme systems.
#css#color#design-tokensRead more - · Lei Li
Hex Encoding for Developers: Color Codes, Byte Arrays, and Debugging Without the Guesswork
A practical guide to hex encoding — how CSS color codes map to bytes, how to read hex dumps when debugging, and the mental model that ties it all together.
#hex#encoding#colorRead more -
CSS Transition vs Animation: A Practical Decision Guide with Timing Function Cheat Sheet
Clear rules for choosing between CSS transition and animation, plus a timing-function cheat sheet covering cubic-bezier, steps(), ease-in, and ease-out with real code examples.
#css#animation#transitionRead more -
CSS Text Effects: Shadows, Gradients, Outlines, and Glow — No Images Needed
A practical guide to CSS text effects using text-shadow, background-clip gradients, -webkit-text-stroke, and filter: drop-shadow. Real code, real output, no plugins.
#css#typography#text-effectsRead more -
CSS oklch() in 2026: Practical Examples, Browser Support, and Why It Beats HSL
A hands-on guide to the CSS oklch() color function — real code examples, browser support data, gamut warnings, and when to use oklch() over hsl() in production.
#css#color#designRead more -
CSS Grid Layout: From Basics to Advanced Real-World Patterns
Master CSS Grid from first principles to production-ready layouts. Covers grid-template-areas, auto-placement, subgrid, and five patterns I use on every project.
#css#grid#layoutRead more -
CSS Gradients with oklch and Lab: Better Color Interpolation with 20 Copy-Paste Examples
Learn how switching CSS gradient interpolation to oklch, lab, or hsl eliminates the muddy midpoint problem — with 20 ready-to-paste linear, radial, and conic gradient examples.
#css#gradients#oklchRead more -
The Complete CSS Gradient Guide: linear-gradient, radial-gradient, and conic-gradient with Real Examples
A practical walkthrough of all three CSS gradient types — linear, radial, and conic — with real code examples, color space interpolation tips, and browser compatibility notes.
#css#gradients#frontendRead more - · Lei Li
CSS Flexbox Layout Recipes: Five Patterns Every Developer Gets Wrong
Five flexbox layout patterns that trip up developers — sticky footers, equal-height cards, centering tricks, flex shrink bugs, and gap vs margin — with exact CSS you can copy.
#css#flexbox#layoutRead more - · Lei Li
CSS Flexbox Cheat Sheet: Every Property, Explained with Real Examples
A complete CSS flexbox property reference — container and item properties, real code examples, common shorthand traps, and visual patterns to bookmark.
#css#flexbox#cheatsheetRead more -
CSS Custom Properties: A Practical Guide to Dynamic Theming Patterns
Learn how to build runtime theme switching, component-scoped variables, and JavaScript-driven theming with CSS custom properties — with real code examples and benchmark data.
#css#custom-properties#variablesRead more -
CSS Custom Properties for Color Tokens: A Practical Design System Tutorial
Learn how to build a scalable color token system with CSS custom properties — from naming conventions to dark mode theming and WCAG validation.
#css#design-system#color-tokensRead more -
CSS Color Contrast for Developers: A Practical WCAG 2.1 Audit Checklist
How to audit, fix, and automate CSS color contrast checks to meet WCAG 2.1 AA — with a real Tailwind gray-400 example, luminance math, and a step-by-step dev workflow.
#css#accessibility#wcagRead more -
CSS box-shadow Reference: Spread, Inset, Multiple Layers, and Neumorphism Patterns
A practical reference for CSS box-shadow — how spread, inset, blur, and color interact, how to stack multiple shadows cleanly, and how neumorphism uses paired shadows to fake depth.
#css#box-shadow#neumorphismRead more -
CSS Border-Radius Explained: How Circles, Pills, and Asymmetric Corners Actually Work
Understand the math behind CSS border-radius circles, pill buttons, and the slash syntax for asymmetric elliptic corners — with copy-ready examples and a live generator.
#css#border-radius#circlesRead more -
HSL vs RGB vs HEX Color Formats in CSS: Which One Should You Actually Pick?
A practical breakdown of HEX, RGB, and HSL color formats in CSS — when each format shines, real conversion examples, and why your choice affects dark mode, theming, and maintainability.
#css#color#web-designRead more -
How to Pick a Website Color Palette: A Color Theory Guide for Developers
A practical walkthrough of color theory for developers — from choosing a seed color to validating contrast ratios and shipping an accessible palette.
#color#css#designRead more -
CSS text-shadow Effects: From Subtle Lift to Full Neon Glow
A practical guide to CSS text-shadow — covering the exact syntax, subtle elevation tricks, multi-layer neon glow recipes, and performance trade-offs.
#css#text-shadow#neonRead more -
20 CSS Gradient Examples: Ready-to-Use Background Patterns with Copy-Paste Code
Twenty battle-tested CSS gradient patterns — hero sections, card overlays, animated buttons, and striped backgrounds — each with copy-paste code and live preview tips.
#css#gradient#backgroundRead more -
CSS Generators Every Frontend Developer Should Bookmark in 2026
Stop writing repetitive CSS by hand. These seven generator tools cover shadows, grids, animations, gradients, and more — with real copy-paste output you can drop straight into production.
#css#tools#frontendRead more -
CSS Box Shadow: Complete Guide with Copy-Paste Examples
A practical CSS box-shadow reference covering syntax, layering, inset shadows, and ready-to-copy code for cards, buttons, and modals — with real browser output.
#css#box-shadow#web designRead more -
CSS Border-Radius Shapes: Pill, Squircle, and Beyond — A Practical Guide
Learn how to create pills, squircles, blobs, and asymmetric shapes with CSS border-radius. Includes copy-paste code examples and a live interactive generator.
#css#border-radius#shapesRead more -
WCAG AA vs AAA Contrast Ratios: A Practical Guide for Product Teams and Marketers
Understand the real difference between WCAG AA (4.5:1) and AAA (7:1) contrast requirements — when each level matters, how to test them, and how to fix failures without wrecking your brand palette.
#accessibility#wcag#designRead more -
OKLCH vs HSL for Accessible Web Palettes: Practical CSS Examples
HSL's lightness value lies to your eyes. OKLCH fixes that. Here's what the difference means for WCAG contrast, palette generation, and your day-to-day CSS workflow.
#css#color#accessibilityRead more -
How to Fix Failing WCAG Contrast Without Changing Your Brand Color
Your brand green fails WCAG AA? You don't have to swap it out. Here's the exact shade-shifting method that passes contrast checks while keeping your color identity intact.
#accessibility#wcag#color-contrastRead more - · Li Lei
Video Bitrate, File Size and Duration: How the Three Numbers Lock Together
Video bitrate, file size and clip length are one equation. Learn the file-size formula, pick a bitrate for any resolution or platform, and balance quality against size.
#video#bitrate#file-sizeRead more - · 李雷
Building a Modular Type Scale: Stop Guessing Font Sizes
A practical guide to modular type scales — why a 1.25 or 1.333 ratio beats hand-picked font sizes, how the base × ratio^step formula works, and how to ship it as CSS variables and rem.
#typography#css#design-systemsRead more - · Li Lei
The Tailwind Cheat Sheet I Actually Keep Open: Utility Classes by Category
A practical Tailwind cheat sheet grouped by category — spacing, flex and grid, typography, colors, plus responsive and state variants — with a worked card example.
#tailwind#css#frontendRead more - · Li Lei
The SVG Wave Divider: How a Smooth Section Edge Is Actually Built
A practical look at how an SVG wave divider is drawn from cubic curves, why layering waves adds depth, and the reasons a vector divider beats a PNG.
#svg#web design#cssRead more - · Li Lei
How to Convert SVG to PNG at the Right Resolution
A practical guide to rasterizing SVG to PNG: choosing an export width, why apps reject SVG, picking 2x for retina, keeping transparency, and converting locally.
#svg#png#image-conversionRead more - · Li Lei
How an SVG Blob Adds Organic Shapes to Modern Web Design
Learn how an SVG blob is built from randomized bezier curves, where to use organic blob shapes in hero accents, avatars and dividers, and why SVG stays crisp.
#svg#web design#blobRead more - · Li Lei
Social Media Image Sizes and Aspect Ratios: The Per-Platform Pixel Guide
Every platform favors a different aspect ratio. Here are the exact pixel sizes for Instagram, X, YouTube thumbnails, and LinkedIn, and why the wrong ratio crops your content.
#social media#aspect ratio#image sizesRead more - · 李雷
RGB to CMYK: Why Your Screen Colors Shift in Print
A practical guide to RGB to CMYK conversion: why screen and print colors differ, the gamut gap behind dull printouts, ICC profiles, and how to prep files for the press.
#color#print#designRead more - · Li Lei
How to Convert px to rem in CSS (And When Each One Wins)
A practical guide to converting px to rem in CSS: the formula, the 16px base, worked examples at 24px/12px/32px, and when to reach for rem, px, or em.
#css#frontend#accessibilityRead more - · Li Lei
Paper Weight Explained: GSM vs US Basis Weight (lb)
Why GSM is the universal way to measure paper weight, how it differs from US basis weight in pounds, and how to convert between them for copy paper, cardstock and more.
#paper#gsm#printingRead more - · Li Lei
Paper Sizes Explained: A4, A3, A5, US Letter and Legal in mm and Inches
A practical guide to A-series and US paper sizes, exact dimensions in mm and inches, and why A4 halves cleanly into A5 for printing and design.
#paper-sizes#printing#designRead more - · 李雷
OKLCH Explained: The Perceptual Color Space That Beats HSL for Ramps
OKLCH is the CSS Color 4 space that makes tints, shades and gradients look evenly spaced. Learn what L, C and H mean, why it beats HSL, and how to convert.
#oklch#css#colorRead more - · Li Lei
Neumorphism, Explained: The Soft UI Shadow Trick and Its One Real Weakness
How the neumorphism (soft UI) look works — two same-color shadows faking depth, why low contrast hurts accessibility, and when the soft style is the right call.
#neumorphism#soft ui#cssRead more - · Li Lei
How to Make a Monogram From Your Initials (and Get the Order Right)
A plain guide to turning initials into a monogram: the traditional surname-in-the-centre order for couples, single vs three-letter marks, and where to use them.
#monogram#design#weddingRead more - · Li Lei
Compress an Image to a Target Size: Hitting an Exact KB Limit Without Guessing
How to compress an image to a target size like 200 KB or 2 MB, with quality auto-tuned to land just under the limit, all processed locally in your browser.
#image#compression#file sizeRead more - · Li Lei
The 140 HTML Color Names Every Developer Should Know (and When to Skip Them)
A field guide to the named CSS colors: how each name maps to a fixed hex value, when named colors beat raw hex, and the odd ones like rebeccapurple.
#css#color#web-designRead more - · Li Lei
How to Normalize Hex Color Codes into One Canonical Form
Normalize hex colors from messy text into one lowercase six-digit form so a design system can diff, dedupe, and search hex color codes that never string-match.
#hex colors#design systems#color normalizationRead more - · Li Lei
How to Validate Hex Color Codes in a Palette or Token File
Validate hex colors from a pasted list or token file. Catch wrong-length codes, non-hex letters, and missing hashes, with a reason beside every row.
#hex colors#color validation#design tokensRead more - · Li Lei
How to Extract Hex Colors From CSS and Build a Clean Palette
Pull every hex color out of CSS or pasted text, dedupe the list, audit a project's real palette, and catch stray off-brand colors fast.
#color#css#paletteRead more - · Li Lei
How to Deduplicate Hex Colors When Shorthand and Case Hide the Real Duplicates
Deduplicate hex color codes the right way: shorthand and uppercase variants of one color survive a plain dedup. Here is how to fold case, expand shorthand, and clean a palette.
#hex colors#color palette#design tokensRead more - · Li Lei
How to Build a Mesh Gradient Background That Actually Looks Designed
A mesh gradient stacks several radial gradients at different positions so color blends in 2D. Here is how it differs from a linear gradient, plus the CSS.
#mesh gradient#css#gradientRead more - · 李雷
The CSS Gradient Guide: Linear, Radial, and Conic Without the Mud
Learn when to use linear, radial, and conic CSS gradients, how color stop positions work, and the one trick that keeps your gradients from going gray in the middle.
#css#gradients#designRead more - · Li Lei
The Golden Ratio in Design and Typography: A Practical Guide to φ ≈ 1.618
How to use the golden ratio (φ ≈ 1.618) for type scales, layout splits, and golden sections — with a worked example, plus an honest look at the myth.
#golden-ratio#typography#designRead more - · 李雷
Glassmorphism CSS: How backdrop-filter Frosted Glass Actually Works
A practical guide to building glassmorphism in CSS with backdrop-filter blur, transparency, and borders — plus readability, performance, and the exact CSS to copy.
#glassmorphism#css#backdrop-filterRead more - · 李雷
Flexbox in Practice: flex-direction, justify-content, and align-items Made Visual
A practical flexbox walkthrough — set the axis with flex-direction, distribute space with justify-content, center with align-items, handle wrap, and copy the generated CSS instantly.
#flexbox#css#frontendRead more - · Li Lei
Editing cubic-bezier Easing Curves by Hand: A Practical Guide to CSS Motion
Learn how a cubic-bezier easing curve actually works — the two control points, reading the curve as speed over time, and exporting a clean cubic-bezier() value.
#css#animation#easingRead more - · Li Lei
How to Normalize CSS Variables So Your Custom Properties Stay in Sync
Normalize CSS variables and custom properties to one kebab-case convention. Trim whitespace, fix the leading --, and keep a design-token file consistent and dedupe-safe.
#css#css-variables#custom-propertiesRead more - · Li Lei
How to Validate CSS Variables: Catch Broken Custom Property Names Fast
Validate CSS variables and custom property names against the real -- prefix and identifier rules, flag broken rows with reasons, and clean a token file.
#css#design-tokens#validationRead more - · Li Lei
Convert a CSS Variable List into JSON, a TypeScript Union, CSV, or SQL IN
Turn a flat list of CSS custom property names into a JSON array, a TypeScript union, CSV, Markdown, or SQL IN list for typed token references and docs.
#css#design-tokens#typescriptRead more - · Li Lei
How to Extract CSS Variables and Custom Properties From a Stylesheet
Pull every --custom-property out of a stylesheet or component file, dedupe the list, and audit which design tokens your CSS actually defines and uses.
#css#design-tokens#custom-propertiesRead more - · Li Lei
How to Deduplicate CSS Variables: Finding Repeated Custom Properties in a Merged Stylesheet
Deduplicate CSS variables fast: spot repeated --token custom property declarations in a merged stylesheet, and handle the case-sensitivity trap that trips most dedupe tools.
#css#custom-properties#design-tokensRead more - · Li Lei
How a CSS Triangle Works: The Border Trick Behind Tooltip Arrows
A plain explanation of the CSS border trick that draws a triangle with no image or SVG, plus how to control direction and size for tooltip arrows and carets.
#css#frontend#tooltipsRead more - · 李雷
Converting CSS to a JS Object: The React Inline Style Guide
Turn CSS declarations into a React inline style object the right way — camelCase keys, vendor prefixes, quoted vs bare numbers, custom properties, and batch conversion.
#css#react#jsxRead more - · Li Lei
How to Make Gradient Text in CSS with background-clip
A practical guide to gradient-filled text in CSS: the background-clip technique, the -webkit- prefix, browser support, and the solid fallback color you must always set.
#css#gradient-text#background-clipRead more - · Li Lei
How CSS Specificity Decides Which Rule Wins (and Why Your Style Isn't Applying)
A practical guide to CSS specificity: the (id, class, element) weighting, why inline styles and !important override, and how to debug style conflicts fast.
#css#specificity#web-developmentRead more - · Li Lei
Crafting Realistic Box Shadows: A Practical Guide to CSS Shadow Depth
How CSS box-shadow really works, what offset, blur, spread, and color each control, and why stacking several soft shadows beats one hard one for realistic depth.
#css#box-shadow#css-shadowRead more - · Li Lei
How to Style a Custom Scrollbar in CSS Without Breaking Firefox
Style a custom scrollbar in CSS that works across Chrome, Safari, Edge, and Firefox — WebKit pseudo-elements, scrollbar-color, cross-browser fallbacks.
#css#scrollbar#frontendRead more - · Li Lei
Pure-CSS Background Patterns: Build a CSS Pattern Without a Single Image
How to make dots, stripes, grids and checkerboards as pure-CSS background patterns with repeating-linear-gradient — resolution-free, tiny, and zero image files.
#css#frontend#designRead more - · Li Lei
Responsive Design With CSS Media Queries: Breakpoints, Mobile-First, and Feature Queries
A practical guide to CSS media queries — common breakpoints, mobile-first min-width vs max-width, prefers-color-scheme dark mode, and other feature queries.
#css#responsive-design#media-queriesRead more - · Li Lei
Pure-CSS Loaders: Build a Crisp Spinner Without a Single GIF
How pure-CSS loaders work, why a CSS spinner beats an animated GIF on weight and crispness, a worked keyframe example, and a reduced-motion accessibility note.
#css#frontend#animationRead more - · Li Lei
How to Truncate Text to N Lines With a CSS Line Clamp
Cut long text to a fixed number of lines with a trailing ellipsis using CSS line clamp. Single-line vs multi-line truncation, a worked example, and card layouts.
#css#line-clamp#frontendRead more - · Li Lei
Building CSS Grid Layouts Visually: Columns, Rows, and the fr Unit
A practical guide to building CSS grid layouts visually — columns, rows, gaps, the fr unit, named template areas, and responsive grids you can ship.
#css#css grid#web layoutRead more - · 李雷
CSS Grid Generator: A Practical Guide to Columns, fr Units and Gap
Learn CSS Grid the way you actually use it — grid-template-columns and rows, the fr unit, gap, and when to reach for Grid over Flexbox. With a real before/after example.
#css#css-grid#frontendRead more - · Li Lei
How to Format CSS: Beautify Minified Stylesheets with a CSS Formatter
Turn minified, one-line CSS back into readable code. A practical guide to indentation, one declaration per line, reading bundled output, and local-only formatting.
#css#formatting#web-developmentRead more - · Li Lei
How to Build a CSS Font Stack With Safe Fallbacks That Survive Every OS
A practical guide to writing a font-family stack: the system font stack, why the generic family at the end matters, and web fonts versus system fonts.
#css#typography#font-familyRead more - · Li Lei
Reading the cubic-bezier() Easing Curve: How Four Numbers Shape a CSS Transition
A practical guide to cubic-bezier() easing in CSS: what the four control points mean, how the curve shapes acceleration, and when a custom curve beats ease-in/out.
#css#animation#easingRead more - · Li Lei
Fluid Typography With CSS clamp(): Scale Font Size by Viewport, Skip the Breakpoints
How CSS clamp() makes font size scale smoothly between a min and max with the viewport, retiring font-size media queries — with a worked heading example.
#css#typography#fluid-typographyRead more - · 李雷
How to Build a CSS Button That Actually Looks Pressable
A practical guide to designing a CSS button: padding, radius, shadow, hover and active states, gradients, and WCAG contrast — with copy-paste CSS you can ship.
#css#buttons#frontendRead more - · Li Lei
How to Find a Complementary Color with the 180-Degree Hue Rotation
Find any color's complement by rotating its HSL hue 180 degrees across the wheel, then branch into analogous, triadic, and split-complementary accent schemes.
#color theory#complementary color#color schemesRead more - · 李雷
Color Shades and Tints: How to Build a 50–950 Scale from One Base Color
Turn a single brand color into a full 50–950 tint and shade scale for your design system. Learn the difference between tints, shades, and tones, plus a real worked example.
#color#design-systems#tailwindRead more - · 李雷
Color Mixer: How to Blend Two Colors by Ratio and Space
A practical guide to using a color mixer: blend two HEX colors by ratio, see why RGB, HSL, and LAB midpoints differ, and pick the right blend for design work.
#color#design#cssRead more - · 李雷
Color Converter Guide: HEX, RGB, HSL, HSV, and CMYK Explained
A practical color converter guide to HEX, RGB, HSL, HSV, and CMYK — what each color space means, when to use which, and a worked #ff8000 conversion.
#color#css#designRead more - · Li Lei
Color Blindness Simulator: Designing Charts and UI That Don't Rely on Color Alone
A practical guide to testing your designs for protanopia, deuteranopia, and tritanopia, and fixing red-green charts that fail for the ~8% of men with color vision deficiency.
#accessibility#color blindness#designRead more - · 李雷
How to Use CSS clip-path for Polygons, Circles, and Insets
A practical guide to CSS clip-path — build polygons, circles, ellipses, and insets, cut diagonal section dividers, make notched ribbons, and animate shapes with copy-paste CSS.
#css#clip-path#frontendRead more - · Li Lei
Chinese Lorem Ipsum: How Chinese Placeholder Text Saves Your Layout
Latin lorem ipsum lies to a CJK layout. Here is why designers and developers need real Chinese placeholder text to test line height, wrapping, and font rendering before launch.
#typography#design#cjkRead more - · 李雷
How to Read a CSS Box Shadow: Every Parameter, Multi-Layer Depth, and the Tricks Behind Shadows That Look Expensive
A hands-on guide to CSS box-shadow: what x, y, blur, spread, and inset each do, how to stack layers for real depth, and the small tweaks that separate cheap shadows from considered ones.
#css#box-shadow#frontendRead more - · 李雷
Border Radius Beyond Four Numbers: 8 Corners, Ellipses, and Blob Shapes in CSS
A practical guide to the full CSS border radius syntax — all eight values, elliptical corners, organic blob shapes, and copy-ready CSS and SVG path output.
#css#border-radius#blob-shapesRead more - · Li Lei
BEM Naming Explained: How block__element--modifier Tames Your CSS
A practical guide to BEM CSS naming. Learn the block__element--modifier syntax, why flat single-class selectors end specificity wars, and how to name components.
#css#bem#naming conventionRead more - · Li Lei
Inlining a Base64 Image in HTML and CSS: When It Helps and When It Hurts
How to encode an image as a Base64 data URI for HTML and CSS, why it adds about 33% size, and when inlining a small icon beats a normal request.
#base64#data-uri#web-performanceRead more - · Lei Li
A Practical Font Pairing Generator Workflow for Brand Systems
Use a font pairing generator with real copy, font loading constraints, contrast checks, and CSS handoff details before choosing type for a brand system.
#typography#design#cssRead more - · Lei Li
Default Profile Images That Feel Intentional
A practical guide to using Toolora's avatar generator for initials, identicons, and geometric default profile images, with a real SVG output example.
#avatar#design#generatorRead more - · Lei Li
Exact image and video sizes
A practical guide to using an aspect ratio calculator before cropping, resizing, compressing, or publishing images and videos.
#image#video#designRead more
Learning & Teaching 17
- · Li Lei
Word Scrambler: How to Scramble Letters for Puzzles, Games, and Classrooms
A practical guide to using a word scrambler to jumble letters for spelling puzzles, party games, and classroom worksheets, plus why scrambled words stay readable.
#word games#spelling#teachingRead more - · Li Lei
The Test Grade Calculator: Turning Wrong Answers Into a Letter Grade
How a test grade calculator turns correct answers into a percentage and letter grade, plus the EZ Grader chart, points vs percentage grading, and curving.
#grading#teaching#ez-graderRead more - · Lei Li
Spanish 500 Essential Words: A Frequency-First Study Plan
A practical English guide to using Toolora's Spanish 500 Essential Words list for first-week Spanish study, pronunciation, search, and review.
#spanish#vocabulary#languageRead more - · Li Lei
Predicting Offspring Genotypes With a Punnett Square
How to read a Punnett square for dominant and recessive alleles, why Aa × Aa gives a 3:1 ratio, and the difference between monohybrid and dihybrid crosses.
#genetics#biology#punnett-squareRead more - · Li Lei
Pig Latin Explained: The Rules, the Worked Examples, and Why It Is a Game, Not a Code
How Pig Latin actually works, with the two simple rules, a worked example, its playful schoolyard history, and why it is a word game rather than a real cipher.
#pig latin#word games#languageRead more - · Li Lei
How to Calculate pH: The Math Behind the 0-14 Acid-Base Scale
A clear guide to calculating pH from hydrogen-ion concentration, reading the 0-14 scale, telling strong from weak acids, and checking your water tests.
#chemistry#ph#acid-baseRead more - · Li Lei
How to Read the Periodic Table: Groups, Periods, and What Each Box Tells You
A plain-English guide to reading the periodic table — how groups and periods organize the 118 elements, what each box shows, and how to spot trends fast.
#chemistry#periodic-table#educationRead more - · Li Lei
Pendulum Period Explained: How T = 2π√(L/g) Works
How a simple pendulum's period works, why mass never matters, the small-angle rule, and why a 1 metre pendulum swings in about two seconds.
#physics#pendulum#calculatorRead more - · Li Lei
Momentum Made Simple: Mass Times Velocity, Collisions, and Impulse
A plain-English guide to momentum: how p = mv works, why momentum is conserved in collisions, how impulse changes it, and why a heavy slow object can match a light fast one.
#physics#momentum#mechanicsRead more - · Li Lei
The Ideal Gas Law, Solved Both Ways: Algebra and a Calculator
How PV = nRT works, how to solve for pressure, volume, moles, or temperature, which gas constant R to use, and when real gases stop obeying the equation.
#chemistry#ideal gas law#physicsRead more - · Li Lei
How Gravitational Force Works: Newton's Law and the Constant Behind It
A plain-English guide to Newton's law of universal gravitation, F=G·m1·m2/r², the gravitational constant, and why the apple falls but the Moon stays in orbit.
#physics#gravity#newtonRead more - · Li Lei
How to Choose a College Major: Matching Interests, Strengths, and Career Goals
A practical guide to choosing a college major by weighing what you enjoy and are good at against career paths and earnings, with a worked example.
#college major#choosing a major#career planningRead more - · Li Lei
Writing Chinese Numbers: From 一二三 to the Anti-Fraud Capitals 壹贰叁
How Chinese numerals work — everyday characters versus financial capitals, why amounts group by ten-thousands, and how to write a cheque amount the bank won't bounce.
#chinese-numbers#numerals#financeRead more - · Lei Li
Tone marks vs tone numbers
A practical guide to choosing tone marks, tone numbers, initials, and separators when converting Chinese text to pinyin for study notes, URLs, and data cleanup.
#pinyin#chinese#languageRead more - · Lei Li
Practical pinyin workflows
A practical English guide to converting Chinese characters to pinyin for study sheets, names, URL slugs, and mixed-language text.
#pinyin#chinese#languageRead more - · Lei Li
Learn German in 100 Days: A Realistic A1 to A2 Plan
30 minutes a day, der/die/das tricks that actually stick, and the strong-verb stem shifts that trip up every beginner. A 100-day plan from zero to a real A2 conversation.
#language#german#tutorialRead more - · Lei Li
25 Free Online Tools for Students (Back-to-School Edition)
Vocabulary lists, cheatsheets, calculators, and quick tests — 25 zero-signup browser tools high school and university students actually use.
#roundup#student#toolsRead more
Guides & Roundups 816
- · Li Lei
UTF-8 vs ASCII vs Unicode: A Practical Guide to Debugging Broken Characters
What mojibake like café actually tells you, how UTF-8, ASCII, and Unicode relate, and a byte-level workflow for finding where text got corrupted.
#utf-8#unicode#asciiRead more - · Li Lei
URL Encoding vs Percent Encoding: When to Use encodeURI, encodeURIComponent, and Form Encoding
Percent encoding, encodeURI, encodeURIComponent, and form encoding are four different things. Learn which one to use where, with real inputs and outputs.
#url-encoding#percent-encoding#javascriptRead more -
URL Encoding vs HTML Entities vs Base64: When to Use Each Text Encoding Method — and How to Layer Them
The context a string lands in decides its encoding. A practical guide to choosing between percent-encoding, HTML entities, and Base64, plus the layering rules that prevent double-encoding bugs.
#encoding#url-encoding#html-entitiesRead more - · Lei Li
Unicode Normalization in Practice: NFC vs NFD vs NFKC vs NFKD for Filenames, Search, and Deduplication
macOS writes filenames in NFD, most of the web uses NFC, and NFKC quietly rewrites ligatures and circled digits. Real code-point examples showing how each form behaves and which one your dedup pipeline actually needs.
#unicode#normalization#NFCRead more - · Li Lei
PostgreSQL Connection Debugging for Web Apps: DATABASE_URL, sslmode, Pool Size, and Deploy Failures
How to debug Postgres connection failures on deploy: percent-encoding in DATABASE_URL, what each sslmode value does, pool size math against max_connections, connect timeouts, and why migrations hang.
#postgresql#database-url#sslmodeRead more - · Li Lei
npm Scripts for Production Deploys: Lifecycle Hooks, npm ci, Lockfiles, and Builds You Can Reproduce
How to structure npm scripts for production: which lifecycle hooks fire when, why npm ci beats npm install in CI, what a lockfile mismatch error actually looks like, and how workspaces change the build command.
#npm#node#deploymentRead more - · Li Lei
JWT Decoding Guide: Header, Payload, Signature, and Safe Base64URL Inspection
Decode a JWT by hand: split the three dot-separated parts, reverse the Base64URL encoding, read the claims, and inspect tokens safely without trusting them.
#jwt#base64url#authenticationRead more - · Li Lei
How to Fix Mojibake and Garbled Text in Files, Forms, CSVs, and Copied Content
A repair playbook for mojibake: reverse é-style corruption, rescue CSVs that Excel mangled, stop forms from double-encoding, and know when the data is truly gone.
#mojibake#encoding#utf-8Read more -
Base64, URL Encoding, and HTML Escaping: Which One Do You Actually Need?
Three different encoding schemes, three different jobs. Learn when to use Base64, percent-encoding, or HTML entity escaping — with real input/output examples.
#encoding#base64#url-encodingRead more -
Percent Encoding for API Query Parameters: Patterns, Pitfalls, and Real Examples
A practical guide to percent encoding complex query parameters in API clients — arrays, nested objects, tokens, and the encoding rules that differ by API style.
#url-encoding#api#query-parametersRead more -
URL Percent-Encoding: Which Characters to Encode, encodeURI vs encodeURIComponent, and Query-String Best Practices
A practical guide to URL percent-encoding: the RFC 3986 safe character set, when to use encodeURI versus encodeURIComponent, and how to build clean query strings without double-encoding bugs.
#url#encoding#javascriptRead more -
Unicode Code Points, UTF-8 Bytes, and UTF-16 Units: Debugging Invisible Characters and Database Column Traps
A developer's practical guide to understanding Unicode code points versus UTF-8 bytes versus UTF-16 code units — with real examples of invisible character bugs, MySQL column sizing errors, and surrogate pair traps.
#unicode#utf-8#utf-16Read more -
Markdown to HTML Rendering: Complete Reference with Spec Differences and Examples
CommonMark, GFM, and original Markdown all render the same input differently. This reference shows exact HTML output for each spec, with real examples and parser comparison.
#markdown#html#renderingRead more -
JavaScript String Escape Sequences: A Complete Guide to \n, \t, \u, and Raw Strings
Understand every JavaScript string escape sequence — \n, \t, \r, \uXXXX, \u{...}, \x, and String.raw — with real code examples, Unicode edge cases, and JSON pitfalls developers hit in production.
#javascript#strings#unicodeRead more -
HTML Entity Encoding vs URL Percent-Encoding vs JavaScript String Escaping: A Context-by-Context Guide
Learn exactly when to use HTML entity encoding, URL percent-encoding, and JavaScript string escaping. Includes a real input/output comparison, a quick-decision table, and the most common mixing mistakes.
Read more -
HTML Character Entities Explained: Named Entities, Numeric Codes, and When to Use Each
Learn the difference between named HTML entities (&amp;), decimal numeric references (&), and hex codes (&) — with real examples and a decision guide for web development.
#html#encoding#web-developmentRead more - · Lei Li
How to Decode a JWT Token Manually: Base64URL Header and Payload Walkthrough
A step-by-step guide to decoding JWT header and payload parts by hand using Base64URL rules, with a real token example, padding fixes, and a browser-based tool for quick inspection.
#jwt#base64#authenticationRead more -
Base64 Encoding Explained: Padding Rules, URL-Safe Variant, and Common Pitfalls for Developers
A practical guide to Base64 encoding — how the alphabet works, why padding matters, when to use the URL-safe variant, and the bugs developers hit most often.
#encoding#base64#web-developmentRead more - · 李雷
Base64 for Images, File Uploads, and API Tokens: A Practical Tradeoff Guide
When should you Base64-encode an image vs. host it separately? When is multipart/form-data better than Base64-in-JSON? Real examples, benchmarks, and the browser btoa() gotchas every web developer should know.
#base64#encoding#imagesRead more -
WCAG AA vs AAA Color Contrast: A Complete Guide with Real Before-and-After Examples
Understand the difference between WCAG 2.1 AA (4.5:1) and AAA (7:1) color contrast requirements, see exact hex pairs that pass and fail, and learn when aiming for AAA is worth the design cost.
#accessibility#wcag#color-contrastRead more -
WCAG Color Contrast Ratios Explained: AA vs AAA Thresholds with Real-World Pass/Fail Examples
A practical breakdown of WCAG AA and AAA contrast thresholds — what the numbers mean, when you need which level, and concrete pass/fail color pairs you can use today.
#accessibility#wcag#color-contrastRead more -
URL Percent-Encoding Explained: Query Strings, Form Data, and RFC 3986 Mistakes
A practical guide to URL percent-encoding: when to use %20 vs +, how RFC 3986 defines safe characters, real encode/decode examples, and the mistakes that silently break APIs.
#url#encoding#web-developmentRead more - · Li Lei
Binary, Hexadecimal, and Octal: The Programmer's Field Guide
A practical guide to binary, hexadecimal, and octal number systems — bitwise operations, color codes, memory addresses, and fast conversion examples with real I/O.
#binary#hexadecimal#octalRead more - · Lei Li
Base64 Encoding: Predicting Output Size for Images, JWT Tokens, and Binary Files
Learn exactly how large your Base64-encoded output will be before you encode it. Real math, real examples, and practical size limits for images, APIs, and JWTs.
#base64#encoding#binary-dataRead more -
UTF-8, UTF-16, and ASCII Demystified: Why JavaScript's String Length Lies
ASCII, UTF-8, and UTF-16 explained from first principles — with exact byte sequences and a clear account of why '😀'.length returns 2 in JavaScript.
#utf-8#utf-16#asciiRead more -
URL Percent-Encoding Complete Guide: Which Characters to Encode and Real-World Gotchas
Learn exactly which characters need percent-encoding in URLs, the difference between reserved and unreserved characters, and the bugs that catch even experienced developers.
#url-encoding#web-development#httpRead more - · 李雷
Percent-Encoding, Query Strings, and the Gotchas That Break Redirects and Webhooks
A developer's guide to URL encoding gotchas: the + vs %20 split, double-encoding in redirect chains, webhook URL corruption, and a fast debugging workflow.
#url encoding#percent encoding#query stringsRead more - · 李雷
URL Encoding Explained: encodeURIComponent, Percent-Encoding, and Query String Pitfalls
The developer's practical guide to encodeURIComponent vs URLSearchParams, why + and %20 are not always interchangeable, and the three query-string bugs that catch even experienced engineers off guard.
#url encoding#encodeURIComponent#percent encodingRead more -
Unicode, UTF-8, UTF-16, and UTF-32: A Byte-Level Breakdown Every Developer Needs
Unicode is a character map, not an encoding. UTF-8, UTF-16, and UTF-32 are three different ways to store that map as bytes. Learn exactly how they differ — with real byte sequences, size tradeoffs, and practical rules for picking the right one.
#unicode#utf-8#utf-16Read more - · Li Lei
HTML Entity Encoding by Context: When to Escape and Which Named Entities to Use
A practical guide to HTML entity encoding — how the right characters and named entities differ between text nodes, attribute values, URL attributes, and script contexts.
#html#encoding#web-developmentRead more -
How to Read Hex, Binary, and Octal When They Show Up in Real Code
A practical guide to hex, binary, and octal as they appear in debuggers, network packets, file permissions, and source code — with real examples you can decode right now.
#hex#binary#octalRead more - · 李雷
Base64 in Practice: Encoding Images, Files, JWTs, and API Tokens (Real Examples)
Four concrete Base64 use cases — inline images, file uploads, JWT decoding, and HTTP Basic auth — with actual input/output pairs and the 33% overhead math.
#base64#jwt#api-authenticationRead more -
Base64 Encoding Explained: Real Use Cases, the 33% Size Overhead, and When to Avoid It
Base64 encodes binary data as ASCII text — but at a 33% size cost. Learn exactly where that overhead comes from, where Base64 is the right tool, and where it quietly hurts performance.
#encoding#base64#web-developmentRead more -
Base64 Encoding Explained: Real Use Cases, Hidden Pitfalls, and When to Skip It
A practical guide to base64 encoding — what it actually does to your bytes, where it genuinely helps, and the three situations where you should reach for something else entirely.
#base64#encoding#web-developmentRead more -
UTF-8 and Unicode Encoding: A Web Developer's Field Guide
How UTF-8 byte sequences work, where encoding bugs hide in real code, and how to inspect code points, URL percent-encoding, and HTML entities without guessing.
#encoding#unicode#utf-8Read more -
URL Percent Encoding Explained: Which JavaScript Function to Use and When
A practical guide to URL percent encoding in JavaScript — when to use encodeURIComponent vs encodeURI vs escape, with real input/output examples and common pitfalls.
#url#encoding#javascriptRead more -
Unicode vs UTF-8 vs UTF-16: What Web Developers Actually Need to Know
Unicode is a standard; UTF-8 and UTF-16 are encodings. This guide explains the practical difference, shows real byte sequences, and helps you debug encoding bugs in web apps.
#unicode#utf-8#utf-16Read more - · 李雷
MD5, SHA-256, or bcrypt: A Practical Guide to Choosing the Right Hash Algorithm
A clear breakdown of MD5, SHA-256, and bcrypt — what each one does, where each fails, and a three-question decision guide to pick the right algorithm for your use case.
#hashing#md5#sha-256Read more -
Markdown Extended Syntax: Tables, Task Lists, Footnotes, and Code Fences Explained
A practical guide to Markdown extended syntax — GFM tables, checkbox task lists, footnotes, and fenced code blocks with real input/output examples.
#markdown#gfm#tablesRead more - · Lei Li
How to Decode and Verify JWT Tokens in the Browser: A Client-Side JavaScript Guide
A practical walkthrough of JWT decoding and verification in the browser — base64url parsing, reading claims with vanilla JS, and using the Web Crypto API for real HMAC-SHA256 signature checks.
#jwt#javascript#browserRead more - · Li Lei
HTML Entity Encoding Cheatsheet: Copy-Paste Codes for & < > and 40+ Characters
A developer quick reference for HTML entity encoding — all three formats for & < > and 40+ named entities, with copy-paste templates for HTML, JSX, and CMS use.
#html#encoding#cheatsheetRead more -
Glob Patterns Explained: Wildcards, Double-Star, and Brace Expansion for Shell, .gitignore, and Bundlers
A practical guide to glob pattern syntax — *, **, ?, [], {} — with real examples for Bash, .gitignore, webpack, and Vite. Learn when each token applies and where the rules differ.
#shell#gitignore#globRead more - · Li Lei
Color Blindness Types Explained: A Designer's Simulation Guide for Deuteranopia, Protanopia, and Tritanopia
Understand exactly how deuteranopia, protanopia, and tritanopia distort color perception, then run a 5-minute simulation audit to catch broken UI before it ships.
#accessibility#color blindness#deuteranopiaRead more -
Base64 Encoding Explained: Data URIs, Binary Transfer, and Real Web API Use Cases
A practical guide to base64 encoding covering data URIs, HTTP binary payloads, and browser Web API patterns — with real input/output examples and performance numbers.
#base64#encoding#data-uriRead more - · Lei Li
Base64 in Web APIs: Encoding Binary for JSON Payloads, File Uploads, and WebSockets
A complete guide to Base64 encoding and decoding in web APIs — why JSON needs it for binary, when file uploads prefer multipart, and how to handle binary WebSocket messages.
#base64#encoding#web-developmentRead more -
Word Count, Character Count, and Readability Scores: What the Numbers Mean for Writers and Developers
A practical guide to word count, character count, and readability scores — what each metric actually measures, real benchmarks, and when the numbers genuinely matter for writers, developers, and content teams.
#writing#readability#word-countRead more - · 李雷
UTF-8 vs ASCII: What Every Web Developer and API Designer Needs to Know
ASCII covers 128 characters. UTF-8 covers over a million. Here is exactly where the gap breaks production code — URL encoding, JSON APIs, HTTP headers — and how to fix each one.
#utf-8#ascii#character-encodingRead more -
URL Percent-Encoding and Form Data: Why + and %20 Are Not the Same
Reserved characters, query string escaping, and the form data encoding pitfall that breaks APIs when you least expect it — explained with real before/after examples.
#url-encoding#percent-encoding#query-stringRead more - · Lei Li
URL Encoding vs Percent-Encoding: A Practical Developer Guide with Real Examples
URL encoding and percent-encoding are often used interchangeably — but they're not identical. This guide covers the RFC differences, shows real encode/decode examples, and explains when each form breaks your API calls.
#url#encoding#web-developmentRead more - · Lei Li
encodeURIComponent vs encodeURI in Practice: When Each One Breaks and Why
JavaScript ships two URL encoding functions that look similar but behave very differently. This guide walks through exactly which characters each one touches, where each one fails, and which one to reach for in real API and browser code.
#url-encoding#javascript#encodeuricomponentRead more -
How to Remove Duplicate Lines from Text: Command-Line, JavaScript, Python, and Browser Tools
Four practical methods to deduplicate text lines — from terminal one-liners to a no-install browser tool. Covers sort -u, awk, Python dict, JavaScript Set, and when to use each.
#text#utilities#command-lineRead more - · Li Lei
HTML Escaping in Modern Frameworks: What React and Vue Handle Automatically (and What They Don't)
React and Vue auto-escape text nodes, but five common patterns bypass that protection. Here is exactly what gets escaped, what doesn't, and how to fill the gaps.
#html#encoding#securityRead more - · Li Lei
HTML Character References: Named Entities, Numeric Codes, and Symbol Encoding Explained
A complete guide to HTML5 character references — how named entities, decimal references, and hex references work, plus a reference table of 15 symbols you'll actually use.
#html#encoding#web-developmentRead more - · Li Lei
Reading Network Packets as Hex: A Practical Debugging Workflow
Learn how hex encoding maps binary data to readable strings, dissect real HTTP and DNS packet bytes, and build a workflow for diagnosing protocol bugs without Wireshark GUI.
#hex#encoding#networkingRead more -
Number Base Conversion Cheatsheet for Developers: Hex, Binary, and Octal
A practical cheatsheet covering hex, binary, and octal conversion for developers. Real tables, working examples, and the mental shortcuts I use daily.
#hex#binary#octalRead more -
Why Emoji Break Your String Length in JavaScript and Python
Emoji expose Unicode code point pitfalls that cause off-by-one bugs, database truncation, and API failures. Here is what every developer needs to know about UTF-8 encoding, surrogate pairs, and safe string length in JavaScript and Python.
#unicode#emoji#javascriptRead more -
Character Encoding Explained: UTF-8, UTF-16, ASCII, and Latin-1 for Web Apps
A practical guide to character encodings — UTF-8, UTF-16, ASCII, and Latin-1 — with real input/output examples and tips for handling international text in web applications.
#encoding#utf-8#unicodeRead more - · 李雷
camelCase vs snake_case vs kebab-case vs PascalCase: JavaScript and Python Naming Conventions Explained
A practical guide to camelCase, snake_case, kebab-case, and PascalCase naming conventions in JavaScript and Python — with real code examples, linter rules, and cross-language pitfalls.
#case-converter#naming-conventions#javascriptRead more -
Base64 Encoding: Real Use Cases, Common Pitfalls, and Browser vs Node.js Differences
A practical guide to Base64 encoding covering when to use it, where it breaks down, and the key API differences between browsers and Node.js — with real input/output examples.
#base64#encoding#javascriptRead more -
Base64 Encoding: How It Works, Real-World Uses, and the Decode Mistakes That Bite Developers
A practical guide to Base64 encoding for web developers — covering the algorithm, real use cases in APIs and CSS, and the most common decoding bugs with fixes.
#base64#encoding#web-developmentRead more - · Lei Li
Base64 Encoding Explained: HTTP Headers, Real Examples, and the Security Trap You Need to Avoid
A practical guide to Base64 encoding covering Authorization headers, data URIs, and the classic mistake of treating Base64 as encryption — with real encode/decode examples.
#base64#encoding#httpRead more - · Lei Li
URL Percent Encoding by Component: Why the Same Character Encodes Differently in Paths, Queries, and Fragments
RFC 3986 gives path segments, query strings, and fragments three different sets of allowed characters. This guide walks through exactly which characters must be percent-encoded in each URL component — with real input/output examples and the bugs you get when you apply the wrong rule.
#url-encoding#percent-encoding#rfc3986Read more - · Lei Li
JWT Security Best Practices in 2026: Common Attacks, Verification Pitfalls, and How to Fix Them
A practical guide to JSON Web Token security: the alg:none bypass, algorithm confusion attacks, weak secrets, missing expiry checks, and what safe verification actually looks like in code.
#jwt#security#authenticationRead more -
Base64 Encoding Explained: Data URIs, JWTs, and API Authentication
A practical guide to Base64 encoding — how it works, why browsers and APIs use it for data URIs and JWTs, and where it shows up in HTTP authentication headers.
#base64#encoding#jwtRead more -
How to Resize Passport and ID Photos to Exact Pixel Specs — No Upload Required
A practical guide to meeting US Passport (600×600 px), EU/Schengen (413×531 px), and China ID (295×413 px) photo requirements without paying a print shop or uploading sensitive images to a cloud service.
Read more -
UTF-8 vs UTF-16 vs ASCII: Character Encoding Explained for Web Developers
A practical guide to ASCII, UTF-8, and UTF-16 encoding — with real byte-level examples showing exactly why your emoji broke and why UTF-8 dominates the web.
#encoding#utf-8#utf-16Read more - · Lei Li
URL Percent-Encoding: The Exact Rules, 5 Common Mistakes, and Real-World Examples
A practical guide to percent-encoding rules from RFC 3986 — which characters must be encoded, which must not be, and the five mistakes that break APIs and search queries in production.
#url#percent-encoding#web-developmentRead more - · Lei Li
How Text Sorting Algorithms Actually Work: Natural Sort, Locale-Aware Sort, and Case Handling
A practical guide to lexicographic, natural, and locale-aware text sorting — with real before-and-after examples, case sensitivity rules, and a decision guide for developers and data wranglers.
#sorting#algorithms#text-processingRead more - · Lei Li
Base64 Encoding Explained: Use Cases, Padding, and the URL-Safe Variant
A practical deep-dive into Base64 encoding for developers — how the alphabet works, why padding exists, when to use the URL-safe variant, and the mistakes that cause silent bugs.
#encoding#base64#web-developmentRead more - · 李雷
OAuth Scopes Explained: How to Pick the Narrowest Permission That Does the Job
A practical guide to OAuth 2.0 scopes across Google, GitHub, Slack, and more — why over-permissioning delays app review, how to read scope strings, and the narrowest-first strategy that keeps consent screens clean.
#oauth#api-security#developer-toolsRead more -
How to Test Color Contrast in a Design System Using CSS Variables and Design Tokens
A practical workflow for auditing WCAG color contrast across an entire design system when your colors live in CSS custom properties and design tokens.
#color-contrast#wcag#css-variablesRead more - · Li Lei
How to Inspect ZIP Contents Before Unzipping: A ZIP Inspector Guide
Read a ZIP file list, sizes, and dates from its central directory without extracting. Inspect zip contents to spot path traversal and surprises before you unzip.
#zip#file-inspection#securityRead more - · Li Lei
Zhuyin (Bopomofo) Explained: Reading ㄅㄆㄇㄈ and Converting It to Pinyin
A learner's guide to Zhuyin (Bopomofo), Taiwan's 37-symbol phonetic system. See how the symbols and tones work and convert between Zhuyin and Pinyin.
#chinese#zhuyin#bopomofoRead more - · Li Lei
Hunting Zero-Width Characters: How Invisible Unicode Breaks Your Text
Zero-width spaces, joiners, and the BOM hide inside text and break comparisons, JSON parsing, and validation. Here is how to find and strip them out.
#unicode#text-cleaning#debuggingRead more - · Li Lei
Zalgo Text Explained: How Glitch Text Corrupts Your Words
How Zalgo text stacks Unicode combining marks to glitch your words, how to control intensity, where to use it, and why it breaks layouts and screen readers.
#zalgo text#glitch text#unicodeRead more - · Li Lei
The Z-Score Explained: How Far From Average Is Your Number?
A plain-English guide to the z-score: how to measure how many standard deviations a value sits from the mean, the 68-95-99.7 rule, and reading percentiles.
#statistics#z-score#standard deviationRead more - · Li Lei
How to Analyze a YouTube Title for Click-Through (Without Becoming Clickbait)
Score a YouTube title the way the algorithm reads it: the 60-character length sweet spot, front-loaded keywords, curiosity gaps, and titles that match the thumbnail.
#youtube#seo#title-optimizationRead more - · Li Lei
How to Read a Yoga Pose Library: Sanskrit Names, Difficulty, and a Beginner Sequence
A practical guide to using a yoga pose library: browse by difficulty, benefit, and body part, decode Sanskrit names, and build a safe beginner sequence.
#yoga#yoga poses#asanasRead more - · Li Lei
Converting YAML to XML: How Keys Become Elements and Lists Become Repeated Tags
A practical guide to converting YAML to XML by hand or with a converter: keys map to elements, lists repeat the parent tag, and attributes vs child elements.
#yaml#xml#data-conversionRead more - · Li Lei
How to Convert YAML to CSV: List of Objects to a Clean Table
Turn a YAML list of objects into a spreadsheet-ready CSV. Keys become columns, list items become rows, nested fields flatten or stay as JSON. Worked example inside.
#yaml#csv#data-conversionRead more - · Li Lei
XML to YAML: How Elements, Attributes, and Text Actually Map Over
A practical guide to converting XML to YAML: how elements become keys, attributes get a prefix, repeated tags turn into lists, and where the ambiguities hide.
#xml#yaml#converterRead more - · Li Lei
XML to CSV, Explained: Repeating Records Become Spreadsheet Rows
A practical guide to converting XML to CSV: how repeating nodes turn into rows, child elements into columns, and how to flatten nested data and legacy feeds.
#xml#csv#data-conversionRead more - · Li Lei
How to Format XML: A Practical Guide to Indenting, Reading, and Validating It
Pretty-print messy XML, read SOAP, RSS, config, and SVG files, check well-formedness, and keep sensitive payloads local with a browser XML formatter.
#xml#formatter#soapRead more - · Li Lei
The Wye-Delta (Star-Delta) Resistor Transformation, Explained
How the wye-delta (Y-Δ, star-delta) resistor transformation cracks bridge networks that have no series-parallel reduction, with both conversion formulas and a worked example.
#electronics#circuit-analysis#resistorsRead more - · Li Lei
The Five Elements Approach to Choosing a Chinese Name
How the wuxing system reads a birth chart for missing elements and picks Chinese name characters of wood, fire, earth, metal, or water to restore balance.
#chinese-naming#wuxing#five-elementsRead more - · Li Lei
Work and Power Explained: From W = F·d to Watts on the Bench
Work and power are not the same thing. This guide walks through W=F·d, P=W/t, joules versus watts, and a 100 N example you can check in seconds.
#physics#mechanics#workRead more - · Li Lei
Work Anniversary Calculator: Years of Service, Exact Tenure, and Your Next Milestone
Count your exact years of service from a hire date, see tenure to the day, and find your next work anniversary — for HR awards, vesting cliffs, and benefits.
#work anniversary#years of service#tenureRead more - · Li Lei
How to Convert Words to Number: Reading Spelled-Out Amounts Back Into Digits
A practical guide to converting number words back into digits — parse cheques, contracts, and transcripts, and handle scales, hyphenated tens, and decimals.
#words to number#number parsing#text to numberRead more - · Li Lei
Word Frequency Counter: How to Find Overused Words and Check Keyword Density
A practical guide to counting word frequency: rank each word by count, fold case, drop stop words, and use density to catch overused words and keyword stuffing.
#word frequency#keyword density#writingRead more - · 李雷
Word Count Explained: Words vs Characters, Reading Time, and Platform Limits
A practical guide to word count: how words differ from characters, how reading time is estimated, how CJK text is counted, and the real character limits for Twitter, SEO meta tags, and more.
#word count#character count#reading timeRead more - · Li Lei
How to Choose a Wire Gauge (AWG) for Your Current Load
A practical guide to picking the right AWG wire gauge for a current load: the inverse AWG scale, ampacity, voltage drop over length, and safety.
#awg#wire gauge#electronicsRead more - · Li Lei
Wind Chill Explained: Why the Cold Feels Worse Than the Thermometer Says
How a wind chill calculator turns air temperature and wind speed into a feels-like number, why wind strips body heat fast, frostbite risk, and dressing smart.
#wind chill#winter safety#frostbiteRead more - · Li Lei
How to Calculate Win Rate (and Why Draws Quietly Change the Math)
A plain-English guide to win rate: the wins-over-total-games formula, where draws belong in the denominator, and how to read streaks and small samples honestly.
#win rate#calculator#gamingRead more - · Li Lei
How a WiFi QR Code Lets Guests Join Without Typing the Password
Make a WiFi QR code so guests scan to connect instead of typing a long password. The WIFI: payload format, WPA vs open vs hidden, and printing it.
#wifi qr code#qr code#wifiRead more - · Li Lei
How to Show Invisible Whitespace: Spaces, Tabs and Hidden Characters
See spaces, tabs, trailing whitespace and non-breaking spaces as visible glyphs. Learn why hidden whitespace breaks YAML, Python and diffs, and how to clean it.
#whitespace#developer-tools#pythonRead more - · Li Lei
How to Size a Wheelchair Ramp Slope to the ADA 1:12 Rule
A practical guide to sizing a wheelchair ramp slope to the ADA 1:12 standard: the run a given rise needs, where landings go, and when a slope is too steep.
#accessibility#wheelchair-ramp#adaRead more - · Li Lei
How to Calculate a Weighted Grade From Homework, Quizzes, and Exams
Compute your course grade from weighted categories, check that your weights sum to 100%, and run what-if plans for the score you need on the final exam.
#weighted grade#course grade#grade calculatorRead more - · Li Lei
The Workout Tracker Habit: How a Weight Training Log Drives Progressive Overload
How keeping a weight training log turns vague effort into real progressive overload, with sets, reps, volume, plateaus, and deloads you can actually see.
#weight training#progressive overload#workout trackerRead more - · Li Lei
How to Write a Weekly Status Report That Your Manager Actually Reads
A practical guide to structuring a weekly report with done, in progress, blockers, and next week — and turning rough bullet notes into a clean, shareable status report fast.
#weekly report#status report#productivityRead more - · Li Lei
What Week Number Is It? ISO 8601 Weeks Explained
Find what week of the year any date falls in, learn the ISO 8601 rule that week 1 holds the year's first Thursday, and use week numbers for cleaner business scheduling.
#week-number#iso-8601#date-calculationRead more - · Li Lei
How to Build a Wedding Budget That Actually Holds Up
Build a wedding budget that survives contact with real vendor quotes: category percentages, why guest count is the biggest cost lever, and tracking estimates against actuals.
#wedding budget#budgeting#personal financeRead more - · Li Lei
Fixing Low-Contrast Text to Pass WCAG: A Practical Guide to the Color Contrast Fixer
How to fix failing text colors so they pass WCAG AA (4.5:1) and AAA (7:1) by nudging lightness while keeping your brand hue, plus large-text exceptions.
#wcag#accessibility#color contrastRead more - · Li Lei
Wavelength and Frequency: The One Equation That Ties Light, Radio, and Sound Together
How c = λf links wavelength and frequency for light, WiFi, and sound. A worked example, the speed-of-light vs sound-speed catch, and the E = hf energy relation.
#physics#wavelength#frequencyRead more - · Li Lei
How Many Rolls of Wallpaper You Actually Need (Pattern Repeat Included)
Plain area-divided-by-coverage math under-buys patterned wallpaper. Here is how rolls are really counted: wall area minus openings, strips per roll, and pattern-repeat waste.
#wallpaper#home-renovation#calculatorRead more - · Li Lei
The Vue 3 Composition API Cheat Sheet I Wish I Had on Day One
A practical Vue 3 cheat sheet for the Composition API — ref vs reactive, computed, watch, lifecycle hooks, props and emits, and template directives like v-if, v-for, and v-model.
#vue#vue3#composition-apiRead more - · Li Lei
Voltage Drop on a Long Wire Run: Why Distance Forces a Thicker Gauge
How voltage drop grows with current and run length, why long runs need thicker wire, the 3% rule explained, and a worked example sizing a 20 A circuit.
#voltage drop#wire sizing#electricalRead more - · Li Lei
The Voltage Divider Formula, Explained for People Who Actually Build Circuits
How a voltage divider taps a mid voltage from two series resistors, the Vout = Vin·R2/(R1+R2) formula, and how to pick resistor values for sensors and references.
#voltage divider#electronics#resistorsRead more - · Li Lei
Vim Commands That Compose: A Survival Guide and Vim Cheat Sheet
Stop fighting Vim. Learn the modes, motions, and verb+motion operators that compose, search and replace, and how to actually quit — with real commands you can copy.
#vim#cheatsheet#developer-toolsRead more - · Li Lei
The Vigenère Cipher Explained: Keyword Encryption That Held for 300 Years
How the Vigenère cipher uses a keyword and modular shifts to beat frequency analysis, with a worked LEMON example, plus why it loses every CTF to Kasiski.
#cryptography#ciphers#ctfRead more - · Li Lei
Learn Vietnamese Words Fast: The 100 Most Useful Vietnamese Vocabulary, Tones, and Script
Start Vietnamese the honest way. The 100 most useful words, the Latin-based script with its six tones, and how to drill them with audio in your browser.
#vietnamese#language-learning#vocabularyRead more - · Li Lei
Car Purchase Tax and the Real Out-the-Door Price: What You Actually Pay Beyond the Sticker
A plain-English guide to vehicle tax, registration, and insurance fees that turn a car's sticker price into a higher out-the-door total — with a worked example.
#car buying#vehicle tax#purchase taxRead more - · Li Lei
Every Vector Operation Explained, With a Free Vector Calculator
Add, subtract, dot, cross, normalize and measure vectors — what the dot and cross products actually mean, with worked numbers and physics, graphics and game uses.
#vectors#linear algebra#physicsRead more - · Li Lei
How to Make a vCard (.vcf) Contact Card People Can Save in One Tap
A plain-English guide to the vCard format: the fields inside a .vcf file, how to share a contact by QR or email, and how to import it to any phone.
#vcard#vcf#contact cardRead more - · 李雷
VAT Explained: Adding Tax, Reverse Calculations, and Net vs Gross Prices
How to add VAT on top of a net price, reverse-engineer the tax inside a gross figure, and read UK and EU VAT rates correctly — with worked £100 and £120 examples.
#vat#tax#financeRead more - · Li Lei
UUIDv7 Explained: The Time-Ordered UUID Your Database Index Will Thank You For
Why UUID version 7 starts with a timestamp, how that makes it sortable and index-friendly for primary keys, and when to pick v7 over random v4.
#uuid#uuidv7#databaseRead more - · Li Lei
UUIDv5 Explained: Deterministic Namespace UUIDs from a Name and SHA-1
How UUIDv5 hashes a namespace UUID plus a name with SHA-1 to make deterministic, idempotent IDs, why the same input always yields the same UUID, and how it differs from random v4.
#uuid#uuidv5#namespace uuidRead more - · Li Lei
How to Normalize UUIDs and Microsoft GUIDs Into One Canonical Form
A UUID can be lowercase hyphenated, uppercase, stripped to 32 hex chars, or brace-wrapped as a GUID — all the same value, none string-equal. Here is how to pick one form.
#uuid#guid#data-cleanupRead more - · Li Lei
How to Validate a UUID List: Format Rules and Cleaning Bad Rows
Validate UUIDs by the 8-4-4-4-12 hex rule, spot malformed rows, and clean a pasted UUID list with a reason beside every flagged line.
#uuid#validation#data-cleaningRead more - · Li Lei
Convert a UUID List to SQL IN, JSON, and TypeScript in One Step
Turn a plain list of UUIDs into a SQL IN clause, JSON array, TypeScript union, CSV, or Markdown for batch DB lookups and typed ID sets, all locally.
#uuid#sql#typescriptRead more - · Li Lei
Reading a UUID: How to Detect Its Version and Variant by Eye
A practical guide to inspecting a UUID — read its version and variant straight from the 8-4-4-4-12 layout, tell v1 from v4 from v7, and pull the timestamp out of v1 and v7.
#uuid#developer-tools#identifiersRead more - · 李雷
UUID v4 vs v7: Which Format Your Database Actually Wants
A practical guide to UUID formats — when v4 random beats v7 time-ordered, the real collision math behind 122 random bits, why v1 is now deprecated, and how to pick keys that won't fragment your index.
#uuid#database#primary-keysRead more - · Li Lei
How to Extract UUIDs From Logs and Text Without Losing Your Mind
Pull every UUID out of a log file or pasted text, dedupe the matches, and export a clean list. A practical guide to the 8-4-4-4-12 hex pattern and local parsing.
#uuid#logs#developer-toolsRead more - · Li Lei
How to Deduplicate UUIDs When Case and Format Variants Hide Copies
A plain text dedup keeps three rows for one UUID when case and braces differ. Here is how to fold those variants and get a clean, copyable list.
#uuid#deduplication#data-cleanupRead more - · Li Lei
How UTM Parameters Decide What Google Analytics Calls Your Traffic
A practical guide to building UTM tracking links, choosing utm_source and utm_medium correctly, and naming campaigns so Google Analytics attributes every click cleanly.
#utm#google-analytics#marketingRead more - · Li Lei
Counting UTF-8 Bytes vs Characters: A Practical Byte Counter Guide
Why an emoji or CJK character takes several UTF-8 bytes, how byte limits like VARCHAR(255) count bytes not characters, and how a byte counter prevents overflow.
#utf-8#encoding#byte counterRead more - · Li Lei
How a Username Generator Builds Handles That Are Memorable and Still Available
A practical guide to building usernames that stick: combine an adjective, a noun, and a short number, check availability across platforms, and keep personal info out.
#username#usernames#online identityRead more - · Li Lei
How to Parse a User-Agent String Into Browser, OS, and Device
A practical guide to parse a User-Agent string into browser, engine, OS, and device — why every browser claims Mozilla, real uses, and where client hints fit.
#user-agent#browser-detection#web-developmentRead more - · Li Lei
How to Extract URL Query Parameters Into a Readable Table
Pull the ?key=value pairs out of any URL into a clean table. A practical guide to auditing UTM tags, debugging links, and decoding query strings.
#url#query-parameters#utmRead more - · Li Lei
How to Parse a URL: A Field Guide to Reading Every Part of a Link
Learn to parse a URL into scheme, host, port, path, query and fragment, read query parameters, and debug tracking links and encoding with a URL parser.
#url#web-development#debuggingRead more - · Li Lei
URL Normalization Explained: When Two URLs Are Really the Same Page
How URL normalization works — lowercase host, drop default port, sort query params, decode escapes — and why it matters for dedup, canonical tags, and caching.
#url#seo#web-devRead more - · Li Lei
How to Validate a URL List: Catch Malformed Links Before You Import
A practical guide to validating a list of URLs in the browser — flag missing schemes, bad hosts, and broken ports row by row, then clean and export the list.
#url#validation#data-cleaningRead more - · Li Lei
How to Extract URLs From Any Block of Text
Pull every http and https link out of messy text, emails, logs, and docs, then dedupe them into a clean list that never leaves your browser.
#url-extractor#text-processing#linksRead more - · 李雷
How to URL Encode Special Characters Without Breaking Your Links
A practical guide to URL encoding: component vs full-URL mode, which characters must be escaped, the + vs %20 trap, and how to spot a double-encoded string before it ships.
#url encode#percent encoding#encodeURIComponentRead more - · Li Lei
How to Deduplicate URLs and Remove Duplicate Links That Only Look Different
Deduplicate URLs the right way. Plain text dedup keeps near-duplicates like trailing slashes, http vs https, and tracking params. Here is what actually matters.
#url#deduplication#data-cleanupRead more - · Li Lei
How to Unslugify: Turn a Slug Back Into a Readable Title
A practical guide to unslugify: convert hyphens and underscores back to spaces, fix capitalization, and turn URL slugs into clean Title Case headings.
#unslugify#slug to title#text toolsRead more - · Li Lei
Price Per Unit, Not Sticker Price: How to Find the Cheaper Pack
Learn to compare unit price across package sizes so the bigger pack does not fool you. Worked example, the formula, and how to normalize grams, litres and pieces.
#unit price#price per unit#grocery shoppingRead more - · Li Lei
The Unit Converter Guide: Metric and Imperial Without the Guesswork
How to convert length, weight, volume, and temperature between metric and imperial, the factors worth memorizing, and why temperature needs an offset, not a multiply.
#unit converter#metric to imperial#temperature conversionRead more - · Li Lei
Why Two Identical-Looking Strings Compare Unequal: A Practical Guide to Unicode Normalization (NFC, NFD, NFKC, NFKD)
Two strings can look the same yet fail an equality check. Here is how Unicode normalization to NFC, NFD, NFKC and NFKD fixes search, dedupe and filenames.
#unicode#text-processing#developer-toolsRead more - · Li Lei
A Practical Guide to the Unicode Inspector: Reading Text by Code Points
Inspect any text character-by-character: code points, names, categories, and UTF-8/UTF-16 bytes. Find hidden zero-width glyphs and look-alike homoglyphs fast.
#unicode#encoding#debuggingRead more - · Li Lei
The ULID Guide: A Sortable, URL-Safe Alternative to the UUID
How a ULID packs a 48-bit timestamp and 80 random bits into 26 Crockford base32 characters, why it sorts by time, and how it stacks up against UUID and UUIDv7.
#ulid#unique-id#databaseRead more - · Li Lei
ULID Decoder Guide: How to Decode a ULID and Read Its Timestamp
Decode a ULID by hand or with a ULID decoder: the 26-char Crockford Base32 layout, extracting the creation time from the first 10 chars, and why ULIDs sort by time.
#ulid#decode-ulid#timestampRead more - · Li Lei
How a Typing Speed Test Measures WPM and Accuracy
How a typing speed test calculates WPM (5 characters = 1 word), what counts as a good speed, why accuracy beats raw speed, and how to practice your way up.
#typing#wpm#productivityRead more - · Li Lei
From TypeScript to Zod: Validate the Data Your Types Can't See
TypeScript types vanish at runtime. Turn your interfaces into Zod schemas to catch malformed API responses and form input before they crash your app.
#typescript#zod#validationRead more - · Li Lei
The TypeScript Type Features You Actually Use Daily: A Quick TypeScript Cheat Sheet
A practical TypeScript cheat sheet covering interfaces vs types, unions and intersections, generics, utility types like Partial and Pick, and type narrowing.
#typescript#types#genericsRead more - · Li Lei
Two's Complement, Explained: How One Bit Signs Your Integers
A plain-English walk through two's complement: how the high bit signs a number, why subtraction becomes addition, how to negate by hand, and how overflow works.
#two's complement#signed integers#binaryRead more - · Li Lei
Twitter Card Meta Tags: How to Make an X Card That Actually Previews
A practical guide to Twitter (X) card meta tags: the required tags, summary vs summary_large_image, the right image size, and how to validate before sharing.
#twitter card#x card#meta tagsRead more - · Li Lei
Turkish Vocabulary the Honest Way: Learn Turkish Words by Their Roots
Learn Turkish words faster by understanding roots, stacked suffixes, vowel harmony, and the phonetic Latin alphabet. Start with the 100 essential Turkish vocabulary.
#turkish#vocabulary#language-learningRead more - · Li Lei
TSV to CSV: How to Convert Tab Delimited Data Without Breaking Your Columns
A practical guide to converting TSV to CSV: swapping tabs for commas, quoting cells that contain commas, escaping quotes, and handling exports from Excel and databases.
#tsv#csv#data conversionRead more - · Li Lei
How to Split Trip Costs Fairly: Settle Shared Expenses in the Fewest Payments
Split expenses on a group trip the clean way: track who paid what, handle uneven shares, and settle up in the fewest possible transfers instead of a payment tangle.
#trip cost splitter#split expenses#group travelRead more - · Li Lei
Transformer Turns Ratio Explained: Np/Ns, Step-Up vs Step-Down, and Why Current Flips
How the transformer turns ratio works: Np/Ns = Vp/Vs, step-up vs step-down, current inverse, and a worked 220V to 12V example for power supply design.
#transformer turns ratio#electronics#power supply designRead more - · Li Lei
Traditional and Simplified Chinese: Why Converting Between Them Is Never a Clean Swap
Traditional Simplified Chinese conversion explained: where each script is used, why one-to-many character mappings break the reverse, and how to localize for TW/HK/Mainland.
#chinese#localization#traditional-chineseRead more - · Li Lei
How to Build a Single-Elimination Tournament Bracket (Seeds, Byes, and Print Day)
Build a single-elimination tournament bracket the right way: how seeding works, why non-power-of-two fields need byes, and how to print a clean chart for game night.
#tournament#bracket#single-eliminationRead more - · Li Lei
How TOTP Authenticator Codes Work: The Shared Secret and the Clock
A plain-English walkthrough of how TOTP turns a Base32 secret and the current time into a 6-digit authenticator code every 30 seconds, fully offline.
#totp#2fa#securityRead more - · Li Lei
How to Convert Text to Title Case Correctly
A practical guide to title case: capitalize major words, keep articles and short prepositions lowercase, and handle AP vs Chicago style for headlines.
#title case#capitalization#headlinesRead more - · Li Lei
How to Read a Tire Size Like 225/45R17 and Compare Two Tires
Decode 225/45R17 into width, sidewall, and overall diameter, then see how a tire swap shifts your speedometer reading and ground clearance.
#tire size#speedometer#car maintenanceRead more - · Li Lei
How to Tip and Split the Bill Without the Awkward Table Math
A plain-English guide to calculating a restaurant tip, splitting the bill among friends, choosing pre-tax vs post-tax tipping, and rounding each share up.
#tip calculator#split the bill#restaurantRead more - · 李雷
Tip Calculator Guide: US Tipping Norms, Tax, and Splitting Bills
How to use a tip calculator the right way — US 15/18/20% norms, whether to tip pre-tax or post-tax, fair AA bill splitting, and how tipping changes country to country.
#tip calculator#tipping#bill splittingRead more - · Li Lei
How to Find a Meeting Time Across Time Zones (and Keep It Fair)
A practical guide to scheduling across time zones: line up working hours, spot the overlap window, dodge DST traps, and rotate the early call fairly.
#time zones#meeting planner#remote workRead more - · Li Lei
How a Time Zone Converter Saves Cross-Team Meetings From DST Mistakes
A practical guide to converting time between zones, scheduling cross-team meetings, avoiding daylight saving traps, and choosing IANA zones over fixed UTC offsets.
#time zones#scheduling#remote workRead more - · 李雷
Unix Timestamp Explained: Seconds, Milliseconds, and the 2038 Problem
A practical guide to reading and converting a Unix timestamp — seconds vs milliseconds, the UTC-versus-local trap, negative epochs, and the Year 2038 overflow that breaks 32-bit systems.
#unix timestamp#epoch time#developer toolsRead more - · Li Lei
Time Duration Calculator: How to Find the Hours Between Two Times Without Slipping on the 60-Minute Hour
Work out the hours between two times for timesheets and shift pay, handle shifts that cross midnight, and avoid the base-10 mistake that breaks manual clock math.
#time#timesheet#payrollRead more - · Li Lei
How to Total Work Hours From a Time Card Without Losing Minutes to Bad Math
A practical guide to adding up clock-in and clock-out times, subtracting unpaid breaks, and converting minutes to decimal hours for payroll without rounding errors.
#time card#work hours#payrollRead more - · Li Lei
How Many Tiles to Buy: A Practical Tile Calculator Guide
Work out how many tiles and boxes to buy for a floor or wall: divide area by tile size, add a 10% waste margin for cuts, and account for grout joints.
#tile calculator#home improvement#flooringRead more - · Li Lei
Three Phase Power Made Simple: kW, kVA, and the √3 Factor
How three-phase power works, why the √3 factor matters, and how to turn line voltage, current, and power factor into kW, kVA, and motor amps.
#three-phase-power#electrical#power-factorRead more - · Li Lei
Learn Thai Words That Stick: A Beginner's Guide to Core Thai Vocabulary
How to learn Thai words the honest way: the most useful core Thai vocabulary, the five tones, Thai script with no spaces, and the polite particles ka and krap.
#thai#language-learning#vocabularyRead more - · Li Lei
Text Wrap vs. Word Wrap: Hard-Wrapping Text to a Column Width Without Breaking Words
How to hard-wrap text to a fixed column width on word boundaries for code comments, plain-text email, and 72-column commit messages, paragraphs intact.
#text-wrap#word-wrap#plain-textRead more - · Li Lei
Text to Speech in the Browser: Hear Your Writing Out Loud
How browser text to speech reads any passage aloud with your system voices, why local synthesis matters, and how rate, pitch, and voice controls help.
#text-to-speech#web-speech-api#accessibilityRead more - · Li Lei
Text to Hex: How Bytes Become Two Hexadecimal Digits Each
How text to hex conversion really works: each byte becomes two hex digits, why UTF-8 multi-byte characters matter, reading hex dumps, and decoding back.
#encoding#hexadecimal#utf-8Read more - · Li Lei
How Text Becomes Binary: Code Points, ASCII, and 8-Bit Bytes Explained
A plain walkthrough of how computers turn text to binary — each character becomes a code point, then 8 bits per byte. Includes a worked example and how to decode back.
#text to binary#encoding#asciiRead more - · Li Lei
How to Sort Lines of Text Alphabetically or Numerically
Sort text lines A-Z, Z-A, or by number in the browser. Learn case-sensitive sorting, dedupe, and why natural sort puts file2 before file10.
#text#sorting#productivityRead more - · Li Lei
Repeat Text the Smart Way: A Practical Text Repeater Guide
How to repeat text or a single character N times with a space, comma, or newline separator, plus real uses for test data, filler, and separators.
#text#productivity#developer-toolsRead more - · Li Lei
How to Clean Text Files: Strip Invisible Junk From Pasted Content
A practical text cleaner guide: remove BOM, null bytes, trailing spaces, stray tabs, and excess blank lines so messy pasted text comes out clean and import-ready.
#text cleaner#clean text#text fileRead more - · Li Lei
How to Compare Text and Read a Text Diff Line by Line
A practical guide to comparing two blocks of text line by line: spot added, removed, and changed lines, proofread drafts, and check config or log edits locally.
#text diff#compare text#proofreadingRead more - · Li Lei
How to Remove Duplicate Lines and Deduplicate Text Without Losing Order
Remove duplicate lines from any list with optional ignore-case and trim-whitespace, keep the first occurrence, and learn when to dedupe instead of sort.
#text#deduplication#productivityRead more - · Li Lei
BPM to Delay Time: Calculating Synced Delay in Milliseconds
How to turn a song's BPM into delay and reverb pre-delay times in milliseconds, with the quarter, eighth, dotted, and triplet note math worked out.
#music-production#mixing#delayRead more - · 李雷
Temperature Converter Guide: Celsius, Fahrenheit, and Kelvin Without the Guesswork
A practical temperature converter walkthrough: the Celsius, Fahrenheit, and Kelvin formulas, easy reference points to memorize, and worked examples for cooking and science.
#temperature#conversion#scienceRead more - · Li Lei
Team Generator Guide: Splitting a Name List Into Fair Random Teams
How a team generator turns a name list into balanced random teams — fixed team count vs fixed team size, the fairness behind the shuffle, and real classroom and sports uses.
#team generator#random teams#group makerRead more - · Li Lei
How to Read Tarot Cards: A Plain Guide to a Digital Tarot Reading
A friendly guide to a digital tarot reading: the 78-card deck, common spreads, and how to read the cards as honest reflection instead of fortune-telling.
#tarot#tarot reading#tarot cardsRead more - · Li Lei
Tap Code Explained: How the Knock Code Sent Words Through Prison Walls
How tap code (the knock code) maps letters to a 5x5 grid where C and K share a cell, how POWs talked by knocking, plus encoding, decoding, and CTF puzzles.
#tap code#knock code#ciphersRead more - · Li Lei
Tally Marks, Decoded: Turning Numbers Into Strokes and Back
How to convert numbers into tally marks and read them back, why counting groups of five works, and where the five-bar gate beats every other counting method.
#tally marks#counting#teaching mathRead more - · Li Lei
Take-Home Pay Explained: Why Net Pay Is Less Than Your Salary Divided by 12
A plain guide to gross vs net pay, pre-tax and post-tax deductions, and how to work out the take-home amount that actually reaches your bank account.
#take-home pay#net pay#salaryRead more - · Li Lei
How to Convert Tabs to Spaces (and Back) Without Breaking Your Code
A practical guide to converting tabs to spaces, choosing the right tab width, and fixing mixed indentation that breaks Python and YAML, all locally.
#tabs to spaces#indentation#code formattingRead more - · Li Lei
How to Write a System Prompt That Anchors Every Reply
A practical guide to writing an effective LLM system prompt: the role, goals, tone, rules, and output format, plus how to test and iterate until it holds.
#prompt engineering#system prompt#llmRead more - · Li Lei
How a Syllable Counter Reads Words, Lines and Haiku
A practical guide to counting syllables in words and text, why a syllable is one vowel sound, and how silent e and diphthongs trip up automatic counting.
#syllables#haiku#poetryRead more - · Li Lei
Swim Pace per 100m and 100yd: Reading, Converting, and Planning Sets
Learn to calculate swim pace per 100m and 100yd, convert between pool lengths and times, plan interval sets, and handle the yards versus meters gap.
#swimming#swim pace#trainingRead more - · Li Lei
SVG to JSX: Turn Any SVG Into a Reusable React Icon Component
Paste an SVG, get a React component. Why JSX needs camelCased attributes, className, and self-closing tags — with a worked example and an icon pattern.
#react#svg#jsxRead more - · Li Lei
How to Optimize SVG Files: A Practical SVG Optimizer Guide
Why exported SVGs are bloated and how to optimize SVG files by stripping editor cruft, metadata, and redundant attributes while keeping the image crisp.
#svg#optimization#web-performanceRead more - · Li Lei
SVG Asset Auditor: How to Run an SVG Audit for Size, Safety, and Accessibility
Audit SVG assets locally for bloated paths, embedded rasters, editor cruft, inline scripts, external references, and missing title/desc accessibility tags.
#svg#security#accessibilityRead more - · Li Lei
The Svelte Cheat Sheet I Wish I Had on Day One
A working developer's tour of Svelte essentials — reactive declarations, props, stores, each and if blocks, two-way binding, and why Svelte compiles itself away.
#svelte#frontend#cheat-sheetRead more - · Li Lei
How to Write Superscript and Subscript Text Anywhere With Real Unicode
Type x² or H₂O into a chat, bio, or spreadsheet using real Unicode superscript and subscript characters that paste cleanly into plain text without HTML.
#text#unicode#superscriptRead more - · Li Lei
How to Generate Printable Sudoku Puzzles by Difficulty (and Why the One-Solution Rule Matters)
Generate printable Sudoku puzzles by difficulty, understand the one-solution rule, see how clue count drives difficulty, and print clean grids for offline play.
#sudoku#puzzles#printableRead more - · Li Lei
Subnet Calculator Basics: Reading a CIDR Block From Mask to Host Count
How a CIDR prefix maps to a subnet mask and host count, how to find the network, broadcast, and usable range, and how to plan IP blocks without guessing.
#networking#subnetting#cidrRead more - · Li Lei
Strip HTML Tags: How to Remove HTML and Get Clean Plain Text
A practical guide to stripping HTML tags down to plain text — removing markup, decoding entities like &, cutting script code, and handling whitespace.
#html#plain-text#text-cleaningRead more - · Li Lei
How to Measure String Similarity: Edit Distance and Fuzzy Matching
Learn how Levenshtein distance, similarity ratios, and Jaro-Winkler power fuzzy matching, deduplication, typo detection, and record linkage in real projects.
#string similarity#levenshtein distance#fuzzy matchingRead more - · Li Lei
From 1RM Estimate to a Real Strength Program: Percentage-Based Training Done Right
Estimate your one-rep max from a hard set, turn it into percentage-based working weights, and program structured progression with deloads that actually work.
#strength training#1rm#percentage based trainingRead more - · Li Lei
Story Points to Hours: An Honest Guide to Agile Estimation and Time
How to translate agile story points into a rough time estimate using your team's velocity, why points are relative not hours, and when not to convert at all.
#agile#estimation#story-pointsRead more - · Li Lei
Stepper Motor Steps per mm, per Revolution, and Microstepping Explained
How to work out stepper motor steps per revolution and steps per mm, what microstepping changes, and how to calibrate motion for 3D printers and CNC.
#3d-printing#cnc#stepper-motorRead more - · Li Lei
The Stefan-Boltzmann Law: How Temperature to the Fourth Power Sets Blackbody Radiation
A practical guide to the Stefan-Boltzmann law and blackbody radiation: P=εσAT⁴, why power scales as T⁴, emissivity, stars, and a worked watt example.
#physics#thermodynamics#blackbody-radiationRead more - · Li Lei
Mean, Median, and the Five Statistics That Describe Any Dataset
A practical guide to descriptive statistics — mean, median, mode, range, variance, and standard deviation — with a worked example and a note on when the median wins.
#statistics#descriptive-statistics#data-analysisRead more - · Li Lei
Startup Runway and Burn Rate: How Many Months of Cash You Actually Have
Work out your startup runway from cash and burn rate, tell gross from net burn, and learn the simple rule for when to start fundraising before the money runs out.
#startup#runway#burn rateRead more - · Li Lei
How to Name Your Startup: A Practical Guide to Brandable Business Names
A hands-on guide to brainstorming startup and business names — portmanteaus, real-word and invented marks, -ly/-ify suffixes, plus domain and trademark checks.
#startup#naming#brandingRead more - · 李雷
How to Calculate Stair Rise, Run, and Slope Before You Cut a Single Board
A practical guide to stair math: how to size risers and treads, apply the 2R+T Blondel comfort formula, stay inside IRC code limits, and check pitch angle with a worked example.
#stairs#construction#diyRead more - · Li Lei
How to Measure Square Footage of Any Room, Even an Awkward L-Shape
Measure the square footage of rooms and irregular spaces the right way: area = length × width, split L-shapes into rectangles, and convert square feet to square meters.
#square footage#area calculator#flooringRead more - · Li Lei
How to Minify SQL: Squash a Query Onto One Line (SQL Minifier Guide)
Minify SQL to one compact line — collapse whitespace, strip comments, and keep string literals intact. A practical guide to using a browser-based SQL minifier.
#sql#minify#developer-toolsRead more - · Li Lei
How to Format SQL: A Practical Guide to Beautifying Queries with an Online SQL Formatter
Format SQL in your browser: uppercase keywords, put each clause on its own line, indent JOINs and subqueries, and turn a one-line ORM query into readable code.
#sql#sql-formatter#developer-toolsRead more - · Li Lei
SQL Commands You Actually Write Daily: A SQL Cheat Sheet for SELECT, JOIN, and GROUP BY
The SQL you write every day — SELECT, WHERE, JOIN types, GROUP BY, aggregates — plus the NULL and JOIN mistakes that quietly break reports, with a quick reference.
#sql#sql-cheat-sheet#sql-joinRead more - · Li Lei
Specific Heat Explained: How Much Energy It Takes to Warm a Thing
A plain-English guide to specific heat and the Q = m·c·ΔT formula — what the numbers mean, why water resists heating, and how to solve for any variable.
#specific heat#physics#calorimetryRead more - · Li Lei
Social Media Character Limits in 2026: A Character Counter for Every Platform
Every platform counts differently. See the real character limits for X, Instagram, LinkedIn, Threads and SMS, how links and emoji count, and how to write within them.
#social media#character counter#writingRead more - · Li Lei
How to Normalize Social Handles: Turn @ Usernames and Profile URLs Into One Clean List
Normalize social handles by stripping the leading @, lowercasing, and pulling the username out of a profile URL so your contact list keeps one canonical row per person.
#social handles#data cleanup#marketingRead more - · Li Lei
How to Validate Social Handles: Catching Bad @ Usernames in a Pasted List
Validate social handles and @ usernames from any pasted list. See the @ + letters, digits, underscores pattern, length caps, and how to clean a messy contact list.
#social handles#text validation#data cleanupRead more - · Li Lei
Extract Social Handles and @Mentions From a Wall of Text
Pull every @handle out of comments, exports, and notes, tell a username apart from an email, dedupe the list, and keep it all in your browser.
#social media#text processing#marketingRead more - · Li Lei
How to Deduplicate Social Handles Without Counting the Same Person Three Times
@User, user, and a profile URL look like three accounts to a plain dedup. Learn what really collapses a handle list and how Toolora's local tool handles it.
#social handles#deduplication#influencer outreachRead more - · Li Lei
How to Decode a Snowflake ID: Pulling Time, Worker, and Sequence Out of 64 Bits
A practical walkthrough of the Snowflake ID bit layout, how to extract the creation timestamp from a Twitter or Discord ID, and why these IDs sort by time.
#snowflake-id#distributed-systems#discordRead more - · Li Lei
Snell's Law of Refraction: How Light Bends, and When It Stops
A plain-English guide to Snell's law, the refraction angle, the critical angle and total internal reflection — with a worked air-to-water example and a free calculator.
#physics#optics#refractionRead more - · Li Lei
Smart Quotes vs Straight Quotes: When to Use Curly Quotes (and When They Break Your Code)
A practical guide to converting between straight and curly quotes: smart apostrophes, em dashes, cleaning pasted text, and why code needs plain ASCII quotes.
#typography#smart quotes#curly quotesRead more - · Li Lei
How to Make Real ꜱᴍᴀʟʟ ᴄᴀᴘs Text for Bios and Social Profiles
Turn plain text into small caps that paste into any bio or post. These are real Unicode glyphs, not a font, with notes on gaps and screen readers.
#small caps#unicode#text generatorRead more - · Li Lei
How a URL Slug Generator Turns Any Title Into a Clean Permalink
Learn how a URL slug generator lowercases titles, swaps spaces for hyphens, strips punctuation, and transliterates accents so your permalinks stay readable and SEO-friendly.
#seo#slug#permalinksRead more - · Li Lei
How to Write a Brand Slogan That Sticks: A Practical Guide to Taglines
What makes a brand slogan or tagline stick — short, benefit-led, rhythmic — plus how to use generated options as starting points and test them on real people.
#slogan#tagline#copywritingRead more - · Li Lei
How to Design a SKU Scheme That Stays Readable, Unique, and Scannable
Design a SKU scheme that encodes category, color, and size into a fixed, readable code. Why sequential-only SKUs fail, and how to keep them unique and scannable.
#sku#inventory#ecommerceRead more - · Li Lei
How to Audit an XML Sitemap Before You Submit It
A practical walkthrough of auditing an XML sitemap: reading urlset and loc, checking lastmod, and catching redirects, 404s, and non-canonical URLs.
#seo#sitemap#xmlRead more - · Li Lei
Simple Interest, Explained: The I = P × r × t Formula and When Loans Actually Use It
How simple interest works, the principal times rate times time formula, a worked example, total repayment, and when loans and bonds skip compounding.
#finance#simple interest#loansRead more - · Li Lei
Significant Figures Explained: How to Count and Round Sig Figs
A plain guide to counting significant figures, the leading and trailing zero rules, and how to round any number to N sig figs without errors.
#significant figures#sig figs#roundingRead more - · Li Lei
How to Convert Shoe Sizes Between US, UK, EU, and cm Without Guessing
A practical guide to converting shoe sizes across US, UK, EU, and cm systems, using foot length in centimetres as the one anchor that brands cannot fudge.
#shoe size#conversion#shoppingRead more - · Li Lei
Chinese Zodiac Compatibility: How the 12 Animals Match, Clash, and Pair Up
A plain guide to Chinese zodiac compatibility — the four trines, the six clashes, and how to check two people's signs without treating the result as fate.
#chinese zodiac#compatibility#shengxiaoRead more - · Li Lei
How to Quote for Shell: A Practical Guide to Shell Escape
Learn why spaces, $, quotes and ; break shell commands or invite injection, how single vs double quotes differ, and how to escape strings safely for bash.
#shell#bash#escapingRead more - · 李雷
Sheet Metal Gauge to Thickness: How to Read mm and Inch Without Ordering the Wrong Coil
A sheet metal gauge is not a fixed thickness. Learn why 18 ga steel, aluminum and stainless differ, how to convert gauge to mm and inch, and how to read a drawing right.
#sheet metal#gauge conversion#fabricationRead more - · Li Lei
Semantic Versioning Explained: When to Bump Major, Minor, or Patch
A practical guide to semantic versioning rules, choosing the right version bump for breaking changes, features, and fixes, plus prerelease tags for npm releases.
#semantic versioning#semver#versioningRead more - · Li Lei
Semantic Versioning Explained: How Semver Numbers Actually Compare
What major.minor.patch mean, how versions compare field by field, why pre-release tags rank lower, and how caret and tilde ranges decide dependency resolution.
#semantic versioning#semver#dependency managementRead more - · Li Lei
Reading Semaphore Flags: How Two Flag Angles Spell Every Letter
A practical guide to flag semaphore: how two flag positions held at clock angles encode each letter, the maritime history behind it, and how to learn it as a puzzle.
#semaphore#flag signaling#maritime historyRead more - · Li Lei
How to Normalize Semantic Versions into Clean, Comparable Semver
Strip the leading v, pad partial versions like 1.2 to 1.2.0, and standardize tags so your semver list sorts and compares correctly every time.
#semver#versioning#developer-toolsRead more - · Li Lei
How to Validate Semantic Versions Against the Semver Spec
Validate semantic versions in a pasted list against the semver spec: catch 1.2, 1.2.x, and leading zeros, then export a clean CSV or JSON report.
#semver#versioning#developer-toolsRead more - · Li Lei
Convert a Version List Into a TypeScript Union, JSON, CSV, or SQL IN: A Guide to the Semantic Version List Converter
Turn a plain list of semantic versions into a TypeScript union type, JSON array, CSV column, Markdown, or SQL IN clause in one step, fully in the browser.
#semver#typescript#devtoolsRead more - · Li Lei
How to Extract Version Numbers From Any Changelog or Log With a Semver Extractor
Pull every semantic version number out of changelogs, logs, and notes, dedupe them, and export a clean list. Local parsing, no upload, with a worked example.
#semver#changelog#versioningRead more - · Li Lei
How to Deduplicate Version Numbers When v1.2.0 and 1.2.0 Are the Same Release
A plain text dedup keeps v1.2.0 and 1.2.0 as two rows. See how to dedupe semver lists so the v-prefix folds and partial versions get flagged instead.
#semver#deduplication#version-numbersRead more - · Li Lei
How to Draw a Fair Secret Santa Without Anyone Drawing Themselves
A practical guide to running a fair Secret Santa: why a valid draw is a derangement, how to exclude couples, and how to send each match privately.
#secret santa#gift exchange#random drawRead more - · Li Lei
The Scytale Cipher: How Spartan Generals Hid Orders on a Rod
The scytale is the oldest transposition cipher: wrap a strip around a rod, read by columns, and the rod diameter is the key. A practical CTF and teaching guide.
#cryptography#ciphers#ctfRead more - · Li Lei
Screw Size Chart Explained: M3, M4, M6 and Gauge Numbers
How metric M screw sizes map to mm diameter, what imperial gauge numbers mean, thread pitch, and tap drill sizes for clean DIY and hardware work.
#screw size chart#metric screws#thread pitchRead more - · Li Lei
How to Score a Scrabble Word: Tile Values, Premium Squares, and the 50-Point Bingo
Learn exactly how a Scrabble score works: fixed letter values, double and triple letter and word squares, the 50-point bingo bonus, and high-value tiles like Q and Z.
#scrabble#word-games#scoringRead more - · Li Lei
The Schwarzschild Radius: How Small a Black Hole Really Is
The Schwarzschild radius R_s = 2GM/c² is the size any mass must be crushed to before it becomes a black hole. The Sun gives 3 km, Earth 9 mm.
#schwarzschild radius#black hole#event horizonRead more - · Li Lei
How to Hit a Savings Goal on a Real Date, Not Someday
Work backward from a savings goal and date to the exact monthly amount, see how interest shrinks it, and why an automatic transfer beats willpower every time.
#savings#personal-finance#budgetingRead more - · Li Lei
How to Pick a Sample Size for a Survey That Actually Holds Up
A practical guide to choosing a survey sample size from confidence level, margin of error, and population, with worked numbers, A/B test sizing, and why bigger rarely helps.
#sample size#survey research#statisticsRead more - · 李雷
US Sales Tax, Explained: Stacking State and Local Rates and Backing Out the Net Price
A practical guide to US sales tax — why rates vary by state, how to stack state and local rates correctly, and how to reverse a tax-inclusive total to find the pre-tax price.
#sales tax#us tax#ecommerceRead more - · Li Lei
Salary to Hourly, the Honest Way: Beyond the 2080-Hour Shortcut
How to convert an annual salary to an hourly wage and back, why the 2080-hour work year is only a starting point, and how to compare a salaried offer to a contract rate.
#salary#hourly wage#compensationRead more - · Li Lei
How to Read a Salary Raise: Percent, Dollars, and the Real Pay Raise After Inflation
Work out a pay raise in percent and dollars, learn why a raise below inflation is a cut, negotiate from the new base, and see how raises compound over a career.
#salary#raise#inflationRead more - · Li Lei
The Rust Cheat Sheet I Reach For: Ownership, Result, match, and Traits
A quick reference to the Rust concepts you actually type day to day — ownership and borrowing, Result and the ? operator, match, Option, traits, and collection methods.
#rust#cheat sheet#error handlingRead more - · Li Lei
The 100 Russian Vocabulary Words That Let You Read a Street Sign First
Learn Russian words the efficient way: the 100 most useful, the Cyrillic letters that fool English readers, why stress and case matter, and how to drill them.
#russian#vocabulary#language-learningRead more - · Li Lei
The Rule of 72: How to Estimate Doubling Time in Your Head
The Rule of 72 turns any interest rate into a doubling time you can compute without a spreadsheet. Here is why it works, where it stays accurate, and how to use it.
#finance#investing#compound-interestRead more - · Li Lei
How to Validate a US Routing Number (ABA) and Catch Typos Before You Send Money
Learn how a 9-digit ABA routing number is built, run the 3-7-1 checksum by hand on a real example, and catch a single-digit typo before an ACH or wire.
#routing number#aba#achRead more - · Li Lei
ROT47 Explained: Rotate Every Visible ASCII Character by 47
How ROT47 rotates all 94 printable ASCII characters by 47, why it hides digits and symbols that ROT13 leaves alone, why it is self-inverse, and where to use it.
#rot47#encoding#asciiRead more - · Li Lei
ROT13 Explained: The Self-Inverse Cipher That Hides Spoilers
ROT13 shifts every letter 13 places, and because the alphabet has 26 letters, running it twice gives you back the original. Here is how and why it works.
#rot13#caesar-cipher#obfuscationRead more - · Li Lei
How to Estimate Roofing Materials by Area and Pitch
Estimate roofing materials by footprint and pitch the right way: turn area into squares, apply the slope factor, add waste, and count shingle bundles.
#roofing#construction#calculatorRead more - · Li Lei
Roof Pitch Explained: Rise Over Run, Degrees, and Rafter Length
How roof pitch works as rise over run (x-in-12), how to convert it to degrees and slope factor, and how to find true rafter length before you cut lumber.
#roof pitch#construction#calculatorsRead more - · Li Lei
How to Write a Date in Roman Numerals (and Read It Back: XXV.XII.MMXXIV)
A plain-English guide to writing dates in Roman numerals: the I V X L C D M symbols, subtractive notation, and how to format day, month and year for tattoos and engravings.
#roman numerals#dates#tattoosRead more - · 李雷
How Roman Numerals Actually Work: I V X L M, Subtraction, and the 3999 Ceiling
Learn the seven Roman numeral letters, the six legal subtractive pairs like IV and IX, why 3999 is the standard ceiling, and where you still meet these numbers daily.
#roman numerals#number systems#referenceRead more - · 李雷
How to Calculate ROI the Right Way (Plus Annualized ROI and ROAS)
A practical guide to ROI: the (gain − cost) / cost formula, why annualized ROI beats dividing by years, how investment and marketing ROI differ, and where ROAS fits in.
#roi#finance#marketingRead more - · Li Lei
The Rocket Equation Explained: How Delta-v Decides Whether You Reach Orbit
A plain-English walk through the Tsiolkovsky rocket equation, delta-v, mass ratio, and why rockets burn so much fuel — with a worked example and a free calculator.
#rocket equation#delta-v#aerospaceRead more - · 李雷
The robots.txt Syntax Guide: User-agent, Allow, Disallow, Sitemap
A practical robots.txt syntax walkthrough covering User-agent, Allow, Disallow, and Sitemap lines, the access-versus-indexing myth, and exactly where the file goes.
#robots.txt#seo#crawlersRead more - · Li Lei
How to Audit a robots.txt File Without Breaking Your Site
A practical guide to auditing robots.txt: reading User-agent, Allow, and Disallow rules, declaring your Sitemap, and avoiding the mistakes that quietly tank crawling.
#SEO#robots.txt#crawlingRead more - · Li Lei
Ring Size Converter: Match US, UK and EU Sizes From a mm Measurement
Convert ring sizes across US, UK and EU systems by measuring your finger in millimetres. A worked example, the proposal sizing trick, and why mm is the only reliable anchor.
#ring size#measurement#jewelryRead more - · Li Lei
How Much to Save Each Month for Retirement: Compound Growth, the 4% Rule, and Inflation
A plain-English retirement savings guide. Project your nest egg with monthly compounding, size a 4% withdrawal income, and beat inflation with real math.
#retirement#personal finance#compound interestRead more - · Li Lei
How to Build a Clean, ATS-Friendly Resume Template That Recruiters Actually Read
A practical guide to building an ATS-friendly resume: the sections that matter, why plain formatting beats fancy design, and how to tailor a resume template per job.
#resume#resume template#atsRead more - · Li Lei
How to Read a Resistor Color Code Without Guessing
A practical guide to reading resistor color code bands. Decode 4 and 5-band resistors with the digit, multiplier, and tolerance scheme, plus which end to start from.
#resistor color code#electronics#resistorsRead more - · Li Lei
Rent vs Buy: How to Find the Year Owning Actually Wins
Renting isn't dead money and buying isn't free equity. Here's how to weigh hidden ownership costs, the break-even horizon, and the opportunity cost of a down payment.
#rent vs buy#personal finance#home buyingRead more - · Li Lei
How Much Rent Can You Afford? The 30% Rule and the 3x Income Test Explained
Work out how much rent you can afford with the 30% rule, the landlord 3x income test, and a debt-aware budget that accounts for utilities and deposits.
#rent affordability#budgeting#personal financeRead more - · Li Lei
How to Remove Line Breaks and Rejoin Wrapped Text
Why pasted PDF and email text breaks mid-sentence, and how to remove line breaks or replace them with spaces while keeping real paragraph breaks intact.
#remove line breaks#text editing#pdf copy pasteRead more - · Li Lei
Remove Accents and Strip Diacritics: Turning café Into cafe
How to remove accents and strip diacritics from text using Unicode NFD normalization, why café becomes cafe, where it helps, and where it quietly hurts.
#text#unicode#diacriticsRead more - · Li Lei
Regular Polygon Math, From Interior Angles to Area and Apothem
How a regular polygon's interior and exterior angles, area, apothem, and circumradius connect, with worked numbers for hexagons, tiling, and bolt circles.
#geometry#regular polygon#areaRead more - · Li Lei
Redis Cheat Sheet: Commands by Data Type, TTL, and Real-World Patterns
A practical Redis cheat sheet covering commands by data type, TTL and expiry, and patterns for caching, rate limiting, and queues, with copy-paste examples.
#redis#cheat sheet#cachingRead more - · Li Lei
How to Scale a Recipe Up or Down (and Where the Recipe Scaler Math Breaks)
Change a recipe's servings the right way: the scale factor, why salt, spices, and bake time don't scale linearly, and a worked 4-to-6 example.
#recipe scaler#cooking#kitchen mathRead more - · 李雷
Reading Time, Explained: How to Turn Word Count Into Honest Minutes
How reading time really works: adult silent reading runs about 200 to 250 wpm, how words convert to minutes, where the 'X min read' badge comes from, and how to time a speech.
#reading time#words per minute#blog writingRead more - · Li Lei
Reading Your Readability Score: What Flesch Reading Ease Actually Tells You
A practical guide to Flesch Reading Ease and Flesch-Kincaid grade level — how sentence length and syllables drive the numbers, how to write for a target grade, and where the metric stops being useful.
#readability#writing#flesch-reading-easeRead more - · Li Lei
RC Time Constant Explained: Tau, the Charge Curve, and the 5τ Rule
How the RC time constant τ = R·C sets capacitor charge and discharge speed, why 1τ is 63%, why 5τ counts as full, and how to size filters and timers.
#electronics#rc circuit#time constantRead more - · 李雷
How to Pick a Random Number You Can Actually Trust
A practical guide to generating a random number with ranges, no-duplicate batches, and raffle sampling — plus why crypto-grade randomness beats Math.random for fair draws.
#random number#rng#raffleRead more - · Li Lei
How to Pick a Random Line From a List Fairly (Random Line Picker Guide)
Pick one or several random lines from any list with equal odds for every entry. Draw giveaway winners, sample data, and learn pick with vs without replacement.
#random line picker#raffle#random samplingRead more - · Li Lei
The Rail Fence Cipher Explained: Zigzag Transposition for CTF and Class
How the rail fence cipher works: write letters in a zigzag across N rails, read them off row by row. A worked 3-rail example, why it isn't secure, and how to crack it.
#rail fence cipher#transposition cipher#ctfRead more - · Li Lei
Quoted-Printable Explained: How Email Encodes Café as caf=C3=A9
How quoted-printable encoding keeps email text readable, escapes non-ASCII bytes as =XX, handles soft line breaks, and when MIME picks it over Base64.
#quoted-printable#email#mimeRead more - · Li Lei
How to Make a QR Code That Actually Scans: URLs, WiFi, Contacts & Text
A practical guide to generating QR codes for URLs, WiFi, and contacts: error-correction levels, payload density, print size, quiet zone, and local generation.
#qr-code#generator#wifiRead more - · Li Lei
How to Scan a QR Code From an Image: A QR Decoder That Reads the Data Locally
Drop a QR image and a QR decoder reads the embedded URL, text, WiFi, or contact so you can see where a code leads before you scan it on your phone.
#qr-code#decoding#privacyRead more - · Li Lei
How to Read a QR Code From an Image: A QR Code Decoder for Checking Links Before You Scan
Use a QR code decoder to read what a QR actually contains—URL, WiFi, contact, or text—before scanning with your phone. Decoding stays local, so the image never uploads.
#qr-code#security#privacyRead more - · Li Lei
The Python Idioms Worth Memorizing: A Practical Python Cheat Sheet
A practical Python cheat sheet for the idioms you reach for daily: comprehensions, slicing, f-strings, enumerate, zip, with statements, and core data structures.
#python#cheatsheet#programmingRead more - · Li Lei
PWM Duty Cycle Calculator: Period, On-Time, and Average Voltage
Turn frequency and PWM duty cycle into period, on-time, off-time, and average voltage. A practical guide for Arduino LED dimming and motor speed control.
#pwm#duty-cycle#arduinoRead more - · Li Lei
Punycode Explained: How Unicode Domains Become xn-- ASCII
How Punycode turns Unicode domain names into ASCII xn-- form, why DNS demands ASCII, and how decoding an xn-- host exposes homograph phishing.
#punycode#idn#dnsRead more - · Li Lei
How to Calculate a Property Management Fee (China HOA Fee Guide)
Work out your monthly and yearly property management fee in China — the per-square-meter rate times your floor area, plus garage, heating and elevator.
#property fee#hoa fee#budgetingRead more - · Li Lei
Building a Personal Prompt Template Library: Reusable AI Prompts That Beat One-Off Typing
Why structured prompt templates with placeholders beat one-off AI prompts, plus a worked summarization template and a simple system for building your own library.
#prompt templates#ai prompts#prompt engineeringRead more - · Li Lei
Projectile Motion Explained: Range, Max Height and Why 45 Degrees Wins
How a projectile motion calculator turns launch speed and angle into range, max height and flight time, and why 45 degrees gives the longest range on flat ground.
#physics#kinematics#projectile-motionRead more - · Li Lei
How to See a Probability Distribution: Normal, Binomial, and Poisson by Shape
Visualize the normal, binomial, and Poisson probability distributions, watch how mean and standard deviation reshape the curve, and read areas straight off the plot.
#probability#statistics#normal distributionRead more - · Li Lei
Present Value Explained: What Future Money Is Worth Today
A plain-language guide to present value: the PV = FV/(1+r)^n formula, picking a discount rate, comparing future cash flows, and making real investment calls.
#present value#time value of money#discount rateRead more - · Li Lei
How a Pregnancy Due Date Is Estimated, and Why Almost No Baby Shows Up On Time
A plain look at how a pregnancy due date is figured: Naegele's rule of LMP plus 280 days, gestational age in weeks, and why so few babies arrive on the exact date.
#pregnancy#due date#gestational ageRead more - · Li Lei
How to Calculate PPI: Pixel Density From Resolution and Screen Size
Work out pixels per inch from any screen's resolution and diagonal size, learn what PPI means for sharpness, and compare phone and monitor displays the right way.
#ppi#pixel density#displaysRead more - · Li Lei
PostgreSQL Cheat Sheet: The psql Meta-Commands and Postgres SQL I Actually Type
A practical Postgres cheat sheet: psql meta-commands, JSONB, generate_series, index types, EXPLAIN ANALYZE, and a safe ON CONFLICT upsert that beats check-then-insert.
#postgresql#psql#jsonbRead more - · Li Lei
How to Normalize Postal Codes and ZIP Codes into One Canonical Spelling
Uppercase UK and Canadian alphanumeric codes, fix the single-space rule, restore dropped ZIP leading zeros, and give your address database one clean spelling per code.
#postal codes#zip codes#data cleaningRead more - · Li Lei
How to Validate Postal Codes and ZIP Codes in a Pasted List
Validate postal and ZIP codes from a pasted list or uploaded file, catch wrong-format rows with a reason beside each one, and clean an address list before import.
#postal-code#data-cleaning#validationRead more - · Li Lei
Convert a Postal Code List to SQL IN, JSON, CSV, and TypeScript: ZIP Codes for Address-DB Queries
Turn a column of postal codes or ZIP codes into a SQL IN clause, JSON array, CSV, Markdown, or TypeScript union for address-DB queries and shipping-zone configs.
#postal-code#zip-code#sqlRead more - · Li Lei
How to Extract Postal Codes and ZIP Codes From Any Block of Text
Pull clean postal and ZIP codes out of address lists, logs, and pasted pages. Learn the formats by country, the false-positive trap, and how local extraction works.
#postal codes#data cleaning#text extractionRead more - · Li Lei
How to Deduplicate Postal Codes and ZIP Codes Without Losing Real Duplicates
Case and spacing variants of UK and Canadian postcodes survive a plain dedup. Here is exactly what the Postal Code Deduplicator folds, what it keeps separate, and why.
#postal codes#deduplication#data cleanupRead more - · Li Lei
Learn Portuguese Words Fast: The 100 Essential Portuguese Vocabulary Cards
A practical guide to the 100 essential Portuguese words, Brazilian vs European differences, nasal vowels, and gendered nouns — with a free study tool.
#portuguese#vocabulary#language-learningRead more - · Li Lei
Pool Volume in Gallons: How to Calculate It for Any Pool Shape
Work out your pool gallons and liters by shape — rectangular, round, oval, or sloped floor — with clear formulas, a worked example, and why volume drives chemicals and heating.
#pool#calculator#water-volumeRead more - · 李雷
The Pomodoro Technique, Honestly Explained: Why 25/5 Works
A practical guide to the Pomodoro Technique — where the 25/5 rhythm came from, why four blocks then a long break, a real day's schedule, and when to bend the rules to 50/10 or 90/15.
#productivity#focus#pomodoroRead more - · Li Lei
The Polybius Square Cipher: How a 5x5 Grid Turns Letters Into Numbers
A practical guide to the Polybius square cipher: how the 5x5 grid maps each letter to a row and column pair, its link to the tap code, and why it still shows up in CTFs.
#cipher#cryptography#ctfRead more - · Li Lei
How to Pluralize English Words Correctly (and Singularize Them Back)
English plural rules made simple: regular -s and -es, consonant plus y to -ies, irregulars like child and mouse, and why pluralize matters in code.
#english#grammar#pluralizeRead more - · Li Lei
The Playfair Cipher Explained: Digraph Substitution on a 5x5 Keyword Square
How the Playfair cipher encrypts letter pairs with a keyed 5x5 grid, the same-row, same-column and rectangle rules, a worked example, and why it is not secure today.
#cipher#cryptography#playfairRead more - · Li Lei
How to Load Barbell Plates: The Plate Loading Math per Side
Work out exactly which barbell plates to load for any target weight. Subtract the bar, halve the rest, and fill each side with the heaviest plates first.
#barbell#plate loading#strength trainingRead more - · Li Lei
How Many Plants Fit Your Bed: A Plant Spacing Guide
Work out exactly how many plants fit a garden bed using square or triangular spacing, why offset rows pack about 15% more, and a worked 3x2 m example.
#gardening#plant spacing#vegetable gardenRead more - · Li Lei
Placeholder Image Generator: Exact Sizes for Mockups and Prototypes
How to make placeholder images at exact dimensions with a size label, why a local generator beats a remote placeholder service, and when to pick SVG over PNG.
#placeholder image#mockups#prototypingRead more - · Li Lei
How to Scale Pizza Dough by Weight Without Guessing
Scale pizza dough with baker's percentages and dough-ball weight. Set hydration for Neapolitan or NY, pick your pizza count, and read exact flour and water grams.
#pizza dough#bakers percentage#hydrationRead more - · Li Lei
The Pigpen Cipher: How a Tic-Tac-Toe Grid Turns Letters Into Secret Symbols
A plain guide to the pigpen cipher: how letters map to grid fragments, its Freemason history, why it is easy to crack, and how to use it for puzzles.
#pigpen cipher#masonic cipher#classical ciphersRead more - · Li Lei
How to Find Piano Chords: Stacking Thirds to Build Any Triad
Learn to find piano chords by stacking thirds. Major vs minor triads, inversions, and reading a chord diagram, with C major and C minor built note by note.
#piano chords#music theory#triadsRead more - · Li Lei
How to Calculate Photon Energy with E = hf = hc/λ
A practical guide to photon energy: the Planck equation, joules versus electronvolts, and a worked 500 nm example landing at about 2.48 eV in the visible band.
#physics#photon energy#planck constantRead more - · Li Lei
How to Normalize Phone Numbers to E.164 Before You Dedupe or Send SMS
Strip spaces, dashes, and parentheses, add the country code, and collapse every messy phone number into one E.164 form so dedupe and SMS actually work.
#phone numbers#data cleanup#E.164Read more - · Li Lei
How to Validate Phone Numbers in a Pasted List Before You Send
Validate phone numbers from a pasted list by digit count and range: catch too-short and too-long entries, understand E.164's 15-digit cap, and why valid shape isn't a working line.
#phone validation#data cleanup#text toolsRead more - · Li Lei
How to Extract Phone Numbers From Messy Text and Build a Clean Contact List
Pull phone numbers out of pasted emails, logs, and exports. Handle country codes, parentheses, and dashes, dodge false positives, and keep it all local.
#phone-numbers#data-cleanup#text-parsingRead more - · Li Lei
How to Deduplicate Phone Numbers When the Same Number Wears Three Formats
Formatting variants slip past a plain text dedup. Learn how to deduplicate phone numbers by normalizing to digits first, and where the line between a true match and a near-twin sits.
#phone numbers#data cleaning#deduplicationRead more - · Li Lei
Pet Food Calculator: How Much to Feed Your Dog or Cat by Calories
How much to feed a dog or cat using RER and MER calorie math, then convert daily calories to cups by your food's kcal density, with a worked example.
#pet food#dog calories#cat feedingRead more - · Li Lei
Dog Years, Decoded: How to Convert Your Pet's Age to Human Years
Why the 'times 7' rule is wrong, how the modern AVMA and size-based curves actually work, and how to read your dog or cat's true age in human years.
#pets#dogs#catsRead more - · Li Lei
How to Read a Percentile: From Test Scores to p99 Latency
A percentile is the value below which k% of your data falls. Learn the rank formula, work through a 90th percentile example, and see where percentiles beat percentages.
#statistics#percentile#data analysisRead more - · Li Lei
Percentage Change Calculator: Increase, Decrease, and Why the Math Is Asymmetric
How to calculate percentage change between two numbers, why percent and percentage points are not the same, and why +25% does not reverse into -25%.
#percentage change#percent increase#percentage pointsRead more - · Li Lei
Percent Yield, Explained: Actual Over Theoretical, and Why Your Reaction Never Hits 100%
How to calculate percent yield with the actual ÷ theoretical × 100 formula, where theoretical yield comes from the limiting reactant, and why lab yields fall short.
#chemistry#percent yield#stoichiometryRead more - · Li Lei
Percent Error, Explained: Measured vs. True Value Without the Guesswork
A clear guide to percent error — the measured-vs-true formula, why we take the absolute difference, lab accuracy thresholds, and how it differs from percent difference.
#percent error#lab accuracy#measurementRead more - · Li Lei
Percent Composition by Mass: How to Read a Formula Element by Element
Learn percent composition by mass, the element mass over molar mass formula, why water is 11.2% H and 88.8% O, and how mass fractions point you to an empirical formula.
#chemistry#percent composition#molar massRead more - · Li Lei
How to Split a PDF Into Separate Files or Pull Out a Single Page
A practical guide to splitting a PDF by page range, extracting one chapter or a single page, and why splitting locally keeps your documents private.
#pdf#productivity#privacyRead more - · Li Lei
How to Check PDF Page Size in Points and Catch Mixed Pages Before Printing
Read PDF page dimensions in points, tell A4 from US Letter, and spot oversized or mismatched pages before a print shop rejects the file. Local inspection.
#pdf#page size#printingRead more - · Li Lei
What Your PDF Metadata Says About You Before You Hit Send
A PDF quietly stores its title, author, creator software, and dates. Read them locally before sharing so you know what a file reveals about you.
#pdf#metadata#privacyRead more - · Li Lei
How to Merge PDF Files in Order Without Losing Quality
A practical guide to merge PDF files into one document, reorder pages before merging, and keep contracts and IDs private by combining everything locally.
#pdf#merge pdf#privacyRead more - · Li Lei
Payment Processing Fee Math: How to Read Stripe & PayPal Fees and Gross-Up to Net Your Target
A plain guide to payment processing fees: the percent-plus-fixed model, the gross-up formula to net any target, and why splitting fees costs you more.
#payments#stripe#paypalRead more - · Li Lei
How Many Pavers Do You Need for a Patio or Walkway
Count pavers for any patio or walkway: divide the area by one paver's face, round up, add 5-10% for cuts, and don't forget the base material underneath.
#pavers#patio#home improvementRead more - · Li Lei
What Actually Makes Password Strength: Length Beats Symbols
Why password length beats complexity, how entropy bits work, why an 80-bit passphrase wins, and why a good checker analyzes your password locally.
#password security#entropy#passphrasesRead more - · Li Lei
Password Leak Checker: How a Pwned Password Lookup Works Without Sending Your Password
How a password leak checker tells you if a password appeared in a known breach, why the k-anonymity range query keeps it private, and what to do when a password shows up.
#security#passwords#privacyRead more - · 李雷
How to Build a Password That Actually Survives a GPU Cracking Rig
A practical guide to strong passwords: how entropy is really calculated, why length beats complexity, and when a passphrase beats a random string — with worked numbers.
#password#security#entropyRead more - · Li Lei
Password Entropy in Bits: What the Number Actually Means
Password entropy explained in bits: how charset size and length set crack time, what the bit thresholds mean, and why length beats added complexity.
#password security#entropy#cryptographyRead more - · Li Lei
How NFL Passer Rating Works: The QB Rating Formula and the 158.3 Ceiling
A plain-English guide to NFL passer rating: the four capped components, the 0 to 158.3 scale, what 158.3 means, and a worked example from a real stat line.
#passer-rating#nfl#quarterbackRead more - · Li Lei
Resistors in Parallel: Why the Total Drops Below the Smallest
How parallel resistors combine, why the total is always smaller than the smallest one, the reciprocal formula, the product-over-sum shortcut, and worked examples.
#electronics#resistors#calculatorRead more - · Li Lei
A Beginner's Guide to Palmistry: Reading the Major Lines and Mounts
A plain-English palm reading guide to the heart, head, life, and fate lines plus the mounts, with a worked example and an honest note on what palmistry can and cannot do.
#palmistry#palm reading#cultureRead more - · Li Lei
How a Palindrome Checker Reads Words, Phrases, and Numbers
A plain-English guide to palindromes: how a checker normalizes case, strips spaces and punctuation, handles numbers, and powers the classic coding-interview question.
#palindrome#text-tools#coding-interviewRead more - · Li Lei
How Much Paint Do I Need? A Room-by-Room Guide to Measuring, Coats, and Buying the Right Amount of Paint
Work out how much paint a room needs: measure wall area, subtract doors and windows, apply coverage per gallon, add coats and primer, then buy whole cans.
#paint#home-improvement#diyRead more - · Li Lei
How to Audit a package-lock.json for Duplicate and Risky Dependencies
A practical guide to auditing your package-lock.json: read the full dependency tree, find duplicate versions and bloat, and spot outdated or risky packages.
#package-lock#dependency audit#npmRead more - · Li Lei
How to Estimate Your Ovulation Day and Fertile Window From Your Cycle
A plain-English guide to estimating ovulation and the fertile window from your menstrual cycle, with the 14-day rule, a 28-day worked example, and why cycle length varies.
#ovulation#fertile window#menstrual cycleRead more - · Li Lei
How to Calculate Overtime Pay: The 1.5x Rule and What It Adds Up To
Learn how overtime pay works: the 1.5x time-and-a-half rule, double-time, the hourly base wage, and how to add regular plus overtime into one correct total.
#overtime pay#payroll#labor lawRead more - · Li Lei
Oven Temperature: Converting Between Fahrenheit, Celsius, Gas Marks, and Fan Settings
Convert oven temperatures between Fahrenheit, Celsius and gas marks, learn why fan ovens run 20°C hotter, and follow recipes from any country with confidence.
#cooking#baking#conversionRead more - · Li Lei
The otpauth URI Behind Every 2FA QR Code, and How to Build One
What the otpauth:// URI is, how its issuer, account and secret parameters work, and how to turn it into a QR code your authenticator app can scan to enroll.
#2fa#otpauth#totpRead more - · Li Lei
How to Turn Any Number Into Its Ordinal (1st, 2nd, 3rd, and Why 11th Breaks the Rule)
A plain-English guide to writing ordinals: the st/nd/rd/th suffix rule, the 11/12/13 exception, plus dates, rankings, and how programmers format them.
#ordinal numbers#grammar#text conversionRead more - · Li Lei
How to Validate an ORCID iD and Catch a Typo Before It Costs You
Understand the 16-digit ORCID iD format, the MOD 11-2 check digit, and how validating one catches typos in citations, submissions, and grant reports.
#orcid#research#check-digitRead more - · Li Lei
Orbital Period Explained: Kepler's Third Law and Why Higher Orbits Are Slower
How orbital period depends on the semi-major axis and central mass, why satellites circle faster than planets, and how to read Kepler's third law T = 2π√(a³/GM).
#orbital period#kepler third law#orbital mechanicsRead more - · Li Lei
How to Audit an OpenAPI (Swagger) Spec Before You Ship the SDK
A practical guide to auditing an OpenAPI or Swagger spec endpoint by endpoint, checking descriptions, responses, auth, and naming so your SDKs and docs come out clean.
#openapi#swagger#api-documentationRead more - · Li Lei
Open Graph Tags: How to Make Your Link Preview Card Look Right
A practical guide to og:title, og:description, og:image and og:url — the meta tags that control how a shared link renders, plus the 1200x630 image and how to check it before posting.
#open graph#link preview#meta tagsRead more - · Li Lei
Setting Op-Amp Gain With Two Resistors: Inverting and Non-Inverting
Set op-amp gain with feedback resistors. Inverting and non-inverting gain formulas, a worked Rf=10k Rin=1k example, and how to pick real resistor values.
#electronics#op-amp#analog-designRead more - · Li Lei
How to Estimate Your One-Rep Max Without Actually Testing a 1RM
Estimate your one-rep max from a lighter set using the Epley and Brzycki formulas, then turn that number into training percentages for every lifting block.
#strength training#one rep max#1RMRead more - · Li Lei
Ohm's Law Made Practical: Solving for Voltage, Current, Resistance, and Power
A working guide to Ohm's law (V=IR) — rearrange it to find current or resistance, add power with P=VI, and follow a worked LED resistor example step by step.
#ohms-law#electronics#calculatorRead more - · Li Lei
The Office Document Metadata You Forget to Remove Before Sharing
A DOCX, XLSX, or PPTX is a ZIP of XML that quietly carries author names, edit history, comments, and tracked changes. Inspect and clear them before you share.
#office#metadata#privacyRead more - · Li Lei
Reading Betting Odds: A Plain Guide to Using an Odds Converter
How to read decimal, fractional and American betting odds, convert between them, find the implied probability, and spot the bookmaker margin hiding in the price.
#odds converter#betting odds#implied probabilityRead more - · 李雷
Number to Words: Cheque Amounts, Big Numbers, and Ordinals
A practical guide to turning a number to words in English — how to write cheque amounts, spell million and billion correctly, and form ordinals without the classic mistakes.
#number to words#cheque amount#ordinalsRead more - · Li Lei
How to Generate a Number Sequence: Ranges, Steps, and Counts
Generate numbers by start, step, and count or end. A practical guide to arithmetic and geometric sequences for test data, IDs, loops, and math practice.
#number sequence#generate numbers#developer toolsRead more - · Li Lei
The Number Formatter Guide: Separators, Decimals, Currency, and Percentages That Don't Break
How to format numbers for reports and spreadsheets across locales: thousands separators, decimal places, currency, percentages, and the comma-vs-period trap.
#number formatting#thousands separator#currencyRead more - · Li Lei
How to Extract Numbers From Messy Text Without Retyping a Thing
Pull every number out of any text — prices, quantities, IDs, decimals, and 1,234-style figures — into a clean list you can paste anywhere, all in your browser.
#text#data-cleaning#developer-toolsRead more - · 李雷
NPV Explained: How to Read Net Present Value, IRR and Payback Together
A plain-English guide to net present value: the NPV formula, how to pick a discount rate, how NPV differs from IRR and payback, and a fully worked cash-flow example.
#npv#net present value#irrRead more - · Li Lei
Managing Node Packages: An npm Commands Cheat Sheet for Real Projects
A practical npm cheat sheet covering install, save-dev, global, scripts, semver ranges (^ vs ~), npm ci vs install, and auditing without the filler.
#npm#node#package-managementRead more - · Li Lei
How to Find the Frequency of Any Musical Note (A4 = 440 Hz)
Work out the note frequency of any pitch from A4 = 440 Hz using equal temperament and the twelfth root of two. Octaves, cents, MIDI, and tuning explained.
#music#audio#frequencyRead more - · Li Lei
How to Calculate Your Net Worth: Assets Minus Liabilities, Tracked Over Time
Net worth is everything you own minus everything you owe. Learn what counts on each side, why income isn't wealth, and how to track the number year over year.
#net worth#personal finance#assets and liabilitiesRead more - · Li Lei
The NATO Phonetic Alphabet: How Alpha Bravo Charlie Stops People Mishearing You
A plain guide to the NATO phonetic alphabet — why Alpha Bravo Charlie beats B/D/P confusion on the phone, how to spell names and codes, plus the full A–Z chart.
#nato phonetic alphabet#spelling alphabet#radio communicationRead more - · Li Lei
The Nashville Number System, Explained for Working Musicians
How the Nashville Number System writes chords as scale degrees 1-7, why session players swear by it, and how to transpose any song in seconds.
#music#chords#nashville number systemRead more - · Li Lei
Nano ID Explained: The Short, URL-Safe Alternative to UUID
Why a 21-character Nano ID matches UUID's collision safety in fewer bytes, how the alphabet and length trade off, and when short IDs beat UUIDs.
#nanoid#uuid#unique-idRead more - · Li Lei
A Random Name Generator for Characters, Test Data, and Pen Names
Use a name generator to spin up realistic first and last name pairs for mockups, fiction, and test fixtures — plus why fake-but-plausible people beat lorem-ipsum filler.
#name generator#random names#test dataRead more - · Li Lei
How to Transpose Music and Change Key Without Rewriting a Single Chord
Transpose music to a new key by moving every note the same number of semitones. Learn singer range, capo vs true transposition, and sharp or flat spelling.
#music#transpose#chordsRead more - · 李雷
How to Read Any Music Interval: Semitones, Cents, and Building Notes from a Root
Learn to name a music interval, count its semitones, read cents, and build a target note from a root. Worked examples with C4, G4, and a major triad.
#music theory#intervals#semitonesRead more - · Li Lei
The Multiplication Table Done Right: Times Tables, the 12×12 Grid, and Tricks That Stick
How the multiplication table actually works, why you only learn half the facts, the ×9 finger trick, and how to print times tables that help kids practice.
#multiplication table#times tables#math educationRead more - · Li Lei
How Much Mulch Do I Need? A Mulch Calculator Field Guide
Work out how much mulch a garden bed needs in cubic yards and bags. Area times depth, the 2–3 inch rule, the cubic-yards formula, and when bulk beats bags.
#gardening#mulch#calculatorRead more - · Li Lei
How to Calculate MPG and Fuel Economy (and Read L/100km Right)
Calculate MPG the tank-to-tank way, convert between MPG and L/100km, and spot the mileage drop that means a maintenance problem before it costs you.
#fuel economy#mpg#car maintenanceRead more - · 李雷
How a Mortgage Calculator Actually Works: Payment, Interest, and Early Payoff
Understand the mortgage payment formula, how principal and interest split each month, and how early payoff and rate changes move the numbers — with a worked $300k example.
#mortgage#home loan#amortizationRead more - · 李雷
How Morse Code Actually Works: Dots, Dashes, and the SOS You Already Know
A practical guide to reading and writing Morse code — the dot/dash rules, the 1:3 timing ratio, the full letter and number chart, why SOS is ... --- ..., and how audio and light send it.
#morse code#telegraphy#ham radioRead more - · Li Lei
How to Find the Moon Phase for Any Date with a Moon Phase Calculator
Look up the moon phase for any past or future date, understand the 29.5-day lunar cycle and its eight phases, and use it for photography, gardening, and stargazing.
#astronomy#moon#stargazingRead more - · Li Lei
Inside a MongoDB ObjectId: 12 Bytes, One Hidden Clock
A practical breakdown of the MongoDB ObjectId — its 12-byte layout, how to decode the embedded creation time, and why _id values sort roughly by time.
#mongodb#objectid#databaseRead more - · Li Lei
The MongoDB Cheat Sheet I Actually Type: Shell Queries, Updates, and Aggregation
A practical MongoDB cheat sheet for the mongosh queries you run daily — find with operators, $set updates, aggregation pipelines, and indexes, with real examples.
#mongodb#cheat-sheet#databaseRead more - · Li Lei
Moment of Inertia Explained: Formulas for Disk, Ring, Rod, and Sphere
How moment of inertia works as rotational mass, why the axis decides everything, and the disk, ring, rod, and sphere formulas with a worked example.
#physics#mechanics#rotational dynamicsRead more - · Li Lei
Molarity Made Simple: From Grams to mol/L Without the Panic
A practical guide to molarity (mol/L): the c = n / V formula, turning mass into moles via molar mass, and weighing out a solution at any target concentration.
#chemistry#molarity#concentrationRead more - · Li Lei
How to Calculate Molar Mass From a Chemical Formula (With Worked Examples)
Learn to compute molar mass by summing each element's atomic weight times its subscript, handle parentheses and hydrates, and convert moles to grams.
#chemistry#molar mass#stoichiometryRead more - · Li Lei
Molality Explained: Moles of Solute per Kilogram of Solvent
Molality is moles of solute per kilogram of solvent (mol/kg). See how it differs from molarity, why it ignores temperature, and how it drives boiling and freezing point shifts.
#chemistry#molality#concentrationRead more - · Li Lei
Modular Exponentiation Explained: Computing a^b mod m Without Overflow
How modular exponentiation works, why square-and-multiply makes a^b mod m fast, and where RSA and crypto rely on it. With a worked 3^200 mod 50 example.
#modular exponentiation#cryptography#number theoryRead more - · Li Lei
Mirror Text Explained: How to Flip Words Into Looking-Glass Letters
What mirror text really is, how reversed-glyph Unicode lookalikes fake a reflection, why it differs from simple backwards text, and where to use it.
#mirror text#text effects#unicodeRead more - · Li Lei
MIME Types Explained: How to Look Up the Content-Type for Any File
A practical guide to MIME types: how to find the Content-Type for a file extension, why the header decides render-vs-download, and the type/subtype format.
#mime-type#content-type#http-headersRead more - · Li Lei
MIDI Note Number 60 Is Middle C: A Producer's Guide to Notes, Numbers, and Hertz
How MIDI note numbers map to note names and frequency: middle C is 60, A4 is 69 at 440 Hz, each semitone adds 1, and why your DAW prints C3 or C4.
#midi#music-production#frequencyRead more - · Li Lei
How to Practice With a Metronome: BPM, Time Signatures, and Clean Technique
A practical guide to practicing with a metronome — what BPM means, how time signatures and accented downbeats work, and why slow practice builds clean speed.
#metronome#practice#musicRead more - · 李雷
Meta Tag Guide: How title, description, OG, and Twitter Card Each Work
A practical breakdown of every SEO meta tag — title, description, Open Graph, and Twitter Card — with real length limits, a worked example, and why OG decides your share card.
#meta tags#seo#open graphRead more - · Li Lei
How to Write a Meta Description That Earns the Click
Write a meta description around 155 characters: front-load the benefit and keyword, add a soft call to action, and lift your search CTR.
#SEO#meta description#copywritingRead more - · Li Lei
How Megapixels Actually Map to Print Size and Crop Room
Work out megapixels from width and height, see how many you need to print at 300 DPI, and learn why a bigger megapixel count is not always the better one.
#photography#printing#image resolutionRead more - · Li Lei
What That Meeting Actually Costs: A Meeting Cost Reality Check
Most meetings have a hidden price tag. Here is the simple formula for meeting cost, a worked example that hits $25,000 a year, and why loaded cost matters.
#meeting cost#productivity#team managementRead more - · Li Lei
Meat Doneness Temperature Guide: Safe and Preferred Internal Cooking Temps
A practical guide to internal meat temperatures: steak doneness from rare to well done, poultry and pork safety minimums, ground meat, and carryover resting.
#cooking#meat temperature#donenessRead more - · 李雷
MD5, SHA-1, and SHA-256 Explained: Which Hash to Actually Use
A practical guide to MD5 vs SHA-1 vs SHA-256 hashes — why MD5 and SHA-1 are broken for security, how hashing differs from encryption, and verifying file integrity.
#hashing#md5#sha-256Read more - · Li Lei
The MBTI Four Letters, Decoded: What a Quick Personality Type Test Can and Cannot Tell You
A plain-English guide to the four MBTI dichotomies (E/I, S/N, T/F, J/P), the 16 types, how to read a sample result, and why MBTI is a conversation starter, not hard science.
#mbti#personality#psychologyRead more - · Li Lei
How a Maze Generator Builds Solvable Printable Puzzles Every Time
How a maze generator guarantees one solvable path, why recursive backtracking and Prim's differ, and how to print sharp mazes for kids, classrooms and games.
#maze generator#printable maze#puzzlesRead more - · Li Lei
Markup vs Margin: The Pricing Mistake That Quietly Eats Your Profit
Markup and margin share the same dollar profit but use different math. Learn the difference, convert between them, and set retail prices that hold.
#pricing#markup#marginRead more - · Li Lei
Generating a Markdown Table of Contents That Actually Links to Your Headings
How a Markdown table of contents is built from your headings, why anchor slugs are lowercased and hyphenated, and how to keep long READMEs navigable.
#markdown#documentation#readmeRead more - · Li Lei
Markdown to Textile: Converting Docs for Redmine and Forum Wikis
A practical guide to converting Markdown to Textile markup for Redmine, Trac and forum wikis, with the heading, bold and code differences that trip people up.
#markdown#textile#redmineRead more - · Li Lei
Markdown to Slack: Why Your Bold Text Breaks in the Channel
Slack speaks mrkdwn, not Markdown. Learn the real differences in bold, italic, links, and headings, and how to convert Markdown to Slack so it renders right.
#markdown#slack#mrkdwnRead more - · Li Lei
Markdown to reStructuredText: A Migration Guide for Sphinx and Read the Docs
Convert Markdown to reStructuredText for Sphinx and Read the Docs. Learn how RST headings, links, and code spans differ, with a worked example and migration tips.
#markdown#restructuredtext#rstRead more - · Li Lei
How to Convert Markdown to Plain Text Without Breaking Your Words
A practical guide to stripping Markdown to plain text — remove hashes, asterisks, and link syntax while keeping readable words and paragraph structure intact.
#markdown#plain text#text processingRead more - · Li Lei
Markdown to Org Mode: Moving Notes into Emacs
A practical guide to converting Markdown to Emacs Org mode: star headlines, slash italics, link syntax, and migrating notes, TODOs, and timestamps.
#markdown#org-mode#emacsRead more - · Li Lei
How to Convert Markdown to JSX for Real React Components
Convert Markdown to JSX for React without an MDX toolchain. See how class becomes className, void tags self-close, and why this beats dangerouslySetInnerHTML.
#markdown#jsx#reactRead more - · Li Lei
Markdown to Jira: A Field Guide to Wiki Markup
Markdown does not work in Jira. Here is how the two markups differ, why headings use h1. and bold uses a single asterisk, and how to paste your notes cleanly.
#markdown#jira#wiki-markupRead more - · 李雷
Markdown to HTML: What Actually Happens to Your Tables, Code Blocks, and Angle Brackets
A practical guide to converting Markdown to HTML — CommonMark vs GFM differences, how tables and fenced code blocks render, why escaping matters, and when to sanitize before shipping.
#markdown#html#commonmarkRead more - · Li Lei
Markdown to Confluence: Why Your Pasted Notes Break and How to Fix Them
Confluence ignores raw Markdown. Here is how its wiki markup works — h1. headings, brace code blocks, double-bar tables — and how to convert MD notes fast.
#markdown#confluence#wiki-markupRead more - · Li Lei
Converting Markdown to BBCode for Forum Posts That Use Bracket Tags
A practical guide to converting Markdown to BBCode for phpBB-style boards, with the full tag mapping for bold, italic, links, code blocks and lists.
#markdown#bbcode#forumsRead more - · Li Lei
Converting Markdown to AsciiDoc: A Practical Migration Guide
Learn how to convert Markdown to AsciiDoc, why AsciiDoc headings use equals signs, and how to migrate your docs into an Asciidoctor or Antora toolchain.
#markdown#asciidoc#documentationRead more - · Li Lei
How to Convert a Markdown Table to CSV Without Breaking Your Columns
Turn a GitHub-flavoured Markdown pipe table into clean RFC 4180 CSV: drop the separator row, split on pipes, quote cells with commas, import into Excel.
#markdown#csv#dataRead more - · Li Lei
How to Build a Markdown Table Without Counting Pipes by Hand
A practical guide to building a Markdown table fast — the header separator row, colon alignment syntax, pasting into GitHub and docs, and editing data in a grid.
#markdown#tables#githubRead more - · Li Lei
How to Extract Markdown Links and Audit Every URL in a Doc
Pull every inline link, reference link, image, and bare URL out of a Markdown file into a clean CSV so you can audit outbound links, find dead ones, and dedupe.
#markdown#links#seoRead more - · Li Lei
A Markdown Editor with Live Preview: Write on the Left, See It Render on the Right
A practical guide to writing READMEs, notes, and docs in a split-pane Markdown editor with live preview, syntax cheats, local processing, and clean export.
#markdown#writing#documentationRead more - · Li Lei
Markdown Syntax for Everyday Writing: A Practical Markdown Cheat Sheet
A hands-on Markdown cheat sheet covering headings, emphasis, lists, links, images, code, tables, and GitHub-flavored extras like task lists and fenced code.
#markdown#markdown syntax#writingRead more - · Li Lei
How to Predict Your Marathon Time From a Shorter Race (Riegel, Pacing, and the Wall)
Predict your marathon finish time from a recent 5K, 10K, or half. Riegel's formula, why the marathon is hardest to call, and how to set race-day pacing.
#running#marathon#race predictionRead more - · Li Lei
How to Build a mailto: Link with a Prefilled Subject and Body
A practical guide to mailto links — encode subject, body, cc and bcc correctly, embed clickable contact links on your site, and know where mailto stops.
#mailto#email#htmlRead more - · Li Lei
How to Split Your Daily Calories Into Macros: Protein, Carbs, and Fat
Turn a daily calorie number into protein, carb, and fat grams using the 4/4/9 rule, common cut/maintain/bulk splits, and a worked 2000 kcal example.
#macros#macronutrients#nutritionRead more - · Li Lei
How to Validate MAC Addresses in a Pasted List Before You Trust It
Validate MAC addresses from a pasted MAC list: confirm 48-bit hex format, catch wrong-length or non-hex rows, and clean a device inventory in the browser.
#mac address#networking#validationRead more - · Li Lei
How to Convert a MAC Address List Into JSON, CSV, and SQL IN
Turn a flat list of MAC addresses into CSV, JSON, Markdown, SQL IN, or a TypeScript union for device inventories, DHCP reservations, and allowlists.
#networking#mac-address#developer-toolsRead more - · Li Lei
How to Extract MAC Addresses From Logs, Exports, and Pasted Text
A practical guide to pulling MAC addresses out of DHCP logs, ARP tables, and switch output, then deduping and normalizing colon, hyphen, and dotted formats locally.
#networking#mac-address#log-analysisRead more - · Li Lei
How to Deduplicate MAC Addresses When Notation and Case Disagree
The same NIC shows up as colon, hyphen, and Cisco-dot notation in different exports. Here is how to deduplicate MAC addresses so one card counts once.
#mac-address#deduplication#networkingRead more - · Li Lei
Reading the Chinese Lunar Calendar: A Practical Guide to Gregorian and Nongli Conversion
How the Chinese lunar calendar works, why lunar dates land on a different Gregorian day each year, how leap months keep it aligned, and how to find festivals and lunar birthdays.
#lunar calendar#chinese calendar#calendar conversionRead more - · Li Lei
How the Luhn Algorithm Catches a Mistyped Card Number
A plain-English walkthrough of the Luhn check (mod 10): doubling every second digit, the worked math, and why one wrong digit always fails the checksum.
#luhn algorithm#checksum#credit cardsRead more - · Li Lei
RC Low Pass Filter Cutoff Frequency: How fc = 1/(2πRC) Works
A practical guide to the RC low pass filter cutoff frequency. Learn fc = 1/(2πRC), the −3 dB point, a worked 1.59 kHz example, and how to pick parts.
#electronics#filters#audioRead more - · Li Lei
How to Generate Random Lottery Numbers for Powerball, 6/49 and Beyond
A plain guide to generating random lottery numbers, why every combination is equally likely, quick pick vs your own numbers, and the honest odds you face.
#lottery#random numbers#powerballRead more - · 李雷
The Lorem Ipsum Generator Guide: History, Why Fake Text Beats Real Text, and How to Generate by Word, Sentence, or Paragraph
A practical guide to Lorem Ipsum: its 2,000-year-old Cicero origin, why designers use scrambled Latin instead of real copy, and how to generate text by word, sentence, or paragraph count.
#lorem ipsum#placeholder text#web designRead more - · Li Lei
How to Analyze Logs Fast: Group Repeated Errors and Find the First Spike
A practical guide to log analysis that groups similar lines, counts each error, filters by level, and finds the first occurrence and spikes in a wall of pasted logs.
#logs#debugging#incident-responseRead more - · Li Lei
Local File Workbench: Process Files Locally, No Upload Required
A browser workbench that reads and triages your files entirely on your device. Inspect types, metadata, and archive risks without uploading a single byte.
#local file workbench#file triage#privacyRead more - · Li Lei
Loan Prepayment: How Extra Payments Pay Off Your Mortgage Early
How extra payments cut a loan's interest and term, why early prepayment saves the most, lump-sum versus monthly extra, and checking for prepayment penalties.
#loan prepayment#mortgage#personal financeRead more - · Li Lei
How to Compare Loan Offers: APR, Total Cost, and the Term Trap
A practical guide to loan comparison — APR vs interest rate, monthly payment tradeoffs, and why a lower rate can still cost you more over a longer term.
#loan comparison#personal finance#mortgageRead more - · Li Lei
How to Estimate LLM API Token Cost Before the Bill Arrives
A practical guide to estimating LLM API costs: the input/output token split, why output tokens cost more, and how to budget a chatbot or batch job at scale.
#llm pricing#api cost#token budgetingRead more - · Li Lei
How to Shuffle a Random List Fairly: A Practical Guide
Shuffle a list, pick winners, or split into teams with verifiably fair randomness. How Fisher-Yates works, why naive shuffles are biased, and real use cases.
#list randomizer#shuffle list#fisher-yatesRead more - · Li Lei
How to Compare Two Lists and Find What Is in Both, Only in A, or Only in B
Compare two lists to find the intersection, items only in A, and items only in B. A practical guide to list comparison for reconciling exports and finding missing items.
#list comparison#compare two lists#set differenceRead more - · Li Lei
A Light Year Is a Distance, Not a Time: How to Convert It
A light year measures distance, not time. Learn to convert light years to km, miles, AU, and parsecs, and build real intuition for interstellar scale.
#astronomy#unit conversion#light yearRead more - · Li Lei
How to Choose and Generate an Open Source License
A practical guide to picking an open source license: permissive MIT, Apache, BSD versus copyleft GPL, what each one permits and requires, and why a missing LICENSE means all rights reserved.
#open source#licensing#developer toolsRead more - · Li Lei
The Thin Lens Equation, Explained Without the Algebra Panic
How the thin lens equation ties object distance, image distance and focal length together, with magnification, sign conventions, and a worked example.
#optics#physics#lens equationRead more - · Li Lei
Leetspeak Explained: How Letters Become 1337 (and Why It Won't Protect Your Password)
A plain guide to leetspeak: the letter-to-symbol swaps behind 1337, where the hacker slang came from, casual vs heavy styles, and why it is no security trick.
#leetspeak#1337#textRead more - · Li Lei
How to Size an LED Strip Power Supply Without Guesswork
Size an LED strip power supply the right way: watts per meter times length, the 20% headroom rule, voltage drop on long runs, and how to pick the right PSU.
#led strip#power supply#electronicsRead more - · Li Lei
How to Size an LED Resistor: The Current-Limiting Resistor Every LED Needs
Why every LED needs a series current-limiting resistor, the R=(Vs-Vf)/If formula, forward voltage and current explained, with an Arduino 5V worked example.
#electronics#led#arduinoRead more - · Li Lei
The Leap Year Rule, Why 1900 Was Not a Leap Year
How the divisible-by-4, century, and 400-year rules decide a leap year, why Feb 29 only sometimes appears, and the off-by-one bugs the rule causes in code.
#leap year#calendar#date mathRead more - · Li Lei
LC Resonance Frequency: How f = 1/(2π√(LC)) Tunes Every Radio and Filter
Understand LC resonant frequency with the formula f = 1/(2π√(LC)), a worked 100 µH / 100 pF example near 1.59 MHz, and how it sets tuning, filters, and RF.
#electronics#rf#lc-circuitRead more - · 李雷
Writing Math with a LaTeX Equation Editor: Syntax, Live Preview, and Export
A practical guide to LaTeX equation syntax — fractions, subscripts, sums, and matrices — plus how live preview and SVG/PNG/MathML export fit academic notes and papers.
#latex#equation editor#mathjaxRead more - · Li Lei
How to Learn Korean Words Fast: The Core Korean Vocabulary That Actually Sticks
Learn Korean words the efficient way. Read Hangul in a day, then drill the core ~100 high-frequency Korean vocabulary that carries most everyday meaning.
#korean#language-learning#vocabularyRead more - · Li Lei
Kinetic Energy and the Square of Speed: Why Doubling Velocity Quadruples the Damage
How kinetic energy works, why KE = ½mv² scales with the square of speed, and what doubling velocity really means for car crashes and projectiles.
#kinetic energy#physics#calculatorRead more - · Li Lei
How Much Kids Allowance to Give: A Parent's Guide to Child Allowance, Chores, and Save/Spend/Give
How much kids allowance to give by age, the dollar-per-year rule, save/spend/give jars, and whether to tie a child allowance to chores or pay it weekly.
#kids allowance#parenting#money habitsRead more - · Li Lei
K/D Ratio Explained: How to Calculate Your Kill Death Ratio (and Why It Lies)
Learn how to calculate K/D ratio and KDA, what counts as a good kill death ratio across shooters, and why K/D alone misses objective play and team value.
#gaming#fps#kd-ratioRead more - · Li Lei
Kaomoji, Explained: How Japanese Emoticons Like the Shrug and Table Flip Actually Work
Kaomoji are upright text faces built from Unicode characters. Learn how they differ from emoji, how to browse them by mood, and where to paste them.
#kaomoji#japanese-emoticons#text-facesRead more - · Li Lei
Kanji Stroke Order Made Simple: The Rules, the Logic, and How to Practice
Learn why stroke order matters for kanji and Chinese characters, the general rules that govern it, and how animated viewing builds real handwriting recall.
#kanji#stroke order#chinese charactersRead more - · Li Lei
How to Normalize JWT Tokens: Strip Bearer Prefixes and Whitespace
Normalize JWT tokens by stripping a leading Bearer prefix and wrapping whitespace to reach the bare header.payload.signature form for clean logging and dedup.
#jwt#tokens#normalizationRead more - · Li Lei
How to Validate JWT Tokens by Checking Their Structure
Validate JWT tokens in bulk by checking their structure - three base64url segments split by dots. Catch malformed tokens fast, and know why structure-valid is not signature-verified.
#jwt#validation#encodingRead more - · Li Lei
Convert a JWT List into CSV, JSON, SQL IN, and TypeScript Union
Turn a plain list of JWT tokens into CSV, a JSON array, SQL IN, or a TypeScript union for test fixtures and logs. Local parsing, masked output, no decode.
#jwt#developer-tools#testingRead more - · Li Lei
How to Extract JWT Tokens From Logs, Headers, and Messy Text
A practical guide to extract JWT tokens from logs, HAR files, and request dumps by their three-dot base64url shape, then dedupe and decode them safely.
#jwt#debugging#authenticationRead more - · Li Lei
How to Deduplicate JWT Tokens From a Captured Log Set
Remove repeated JWT tokens from merged logs and exports. Learn why JWTs dedupe by exact base64url match, why you normalize first, and how masking keeps output safe.
#jwt#deduplication#logsRead more - · Li Lei
How a JWT Is Built: Header, Payload, and the Signature That Makes It Trusted
A practical look at building a JSON Web Token by hand: the three base64url parts, registered claims like exp and iat, and why the signature is what your server checks.
#jwt#encoding#authenticationRead more - · 李雷
How to Decode a JWT: Read the Header, Payload, and Signature Yourself
Learn how to decode a JWT by hand, what each of the three segments holds, and why decoding is not the same as verifying. Includes a worked example and the exp/iat claims that trip up most debugging.
#jwt#authentication#debuggingRead more - · Li Lei
The Julian Date Explained: One Number Astronomers Use to Count Every Day
What the Julian Date is, how to convert it to and from a calendar date, why astronomers count days instead of months, and how it differs from the Julian calendar.
#astronomy#dates#timeRead more - · Li Lei
JSON to Java Classes: Generate POJOs, Records, and Lombok @Data
Convert any JSON payload into typed Java classes with Jackson or Gson annotations, correct boxing, nested objects, and generated getters and setters.
#json to java#java#jacksonRead more - · 李雷
JSON to CSV: Flattening Nested Objects, Arrays, and the Excel Encoding Trap
A practical guide to converting JSON to CSV — how nested objects flatten to dotted columns, how arrays and missing fields are handled, RFC 4180 escaping, and the UTF-8 BOM that stops Excel mangling Chinese text.
#json to csv#csv#data conversionRead more - · Li Lei
Structured Data with JSON-LD: How Schema.org Markup Earns Rich Results
A practical guide to JSON-LD structured data: the script tag, schema.org types like Article, Product, FAQ and Organization, and why it helps SEO.
#json-ld#structured-data#schema-orgRead more - · Li Lei
How to Obfuscate JavaScript: What a JS Obfuscator Actually Does
A plain look at how a JS obfuscator works, why obfuscating JavaScript is deterrence not security, and how it differs from minifying for size.
#javascript#obfuscation#web developmentRead more - · Li Lei
Jet Lag, Explained: How Many Days Recovery Really Takes and How to Adjust Faster
Why crossing time zones wrecks your sleep, how to estimate jet lag recovery at roughly a day per zone, why eastward is harder, and how light fixes it.
#jet lag#travel#sleepRead more - · Li Lei
How to Learn Japanese Words: The First 100 Vocabulary That Unlock Real Conversation
A beginner's guide to Japanese vocabulary: the 100 essential words, the three writing systems, romaji, particle basics, and how to drill them with audio.
#japanese#vocabulary#language-learningRead more - · Li Lei
Italian Vocabulary for Beginners: Learn Italian Words You Will Actually Say
Why a tight core of Italian vocabulary beats endless flashcards. Phonetic spelling, il/la gender, Latin roots, and a tool to learn Italian words fast.
#italian#vocabulary#language-learningRead more - · Li Lei
How to Validate an ISSN: The 8-Digit Journal Number and Its Check Digit
An ISSN is 8 digits with a MOD 11 check digit (X means 10). Learn the format, compute the check character by hand, and tell it apart from an ISBN.
#issn#validation#check-digitRead more - · Li Lei
How to Normalize Dates to ISO 8601 (YYYY-MM-DD) Without Breaking Your Sorts
Mixed date formats like 03/04/2024 are ambiguous and wreck sorting and dedup. Here is how ISO 8601 fixes it and how to normalize a messy list in your browser.
#iso-8601#dates#data-cleanupRead more - · Li Lei
How to Validate ISO Dates in a Pasted List and Catch Fake Calendar Days
Validate ISO 8601 dates in a pasted date list: check the YYYY-MM-DD shape and that each date is a real calendar day, then export a clean report.
#iso 8601#date validation#data cleaningRead more - · Li Lei
How to Extract ISO Dates From Logs and Text Without a Script
Pull every ISO 8601 date and timestamp out of a log or block of text, dedupe them, and build a clean timeline. Runs locally in your browser.
#iso-8601#dates#logsRead more - · Li Lei
Deduplicate Dates the Right Way: Build a Clean Unique Dates List
A plain dedup keeps 2024-03-04 and 2024-3-4 as two rows even though they're the same day. Here's how to fold format variants into one canonical date.
#dates#data-cleaning#iso-8601Read more - · Li Lei
How to Validate an ISBN: ISBN-10, ISBN-13, and the Check Digit Math
A practical guide to validating an ISBN by hand or with a tool: the ISBN-10 mod-11 check, the ISBN-13 mod-10 check, converting between them, and catching catalog typos.
#isbn#check-digit#data-validationRead more - · Li Lei
Converting Between ISBN-10 and ISBN-13: The 978 Prefix and Check Digit, Explained
How to convert an ISBN-10 to an ISBN-13 and back: prepend 978, recompute the check digit, handle the X and 979 cases, and keep library records clean.
#isbn#book-metadata#catalogingRead more - · Li Lei
How to Validate IPv6 Addresses and Clean an IPv6 List
Validate IPv6 addresses in a pasted list: catch nine groups, two double-colons, and bad hex characters, then export a clean per-row report.
#ipv6#networking#validationRead more - · Li Lei
How to Extract IPv6 Addresses From Logs and Messy Text
A practical guide to pulling IPv6 addresses out of logs and pasted text: the colon-hex format, :: compression, why they hide better than IPv4, and clean dedup.
#ipv6#networking#log-analysisRead more - · Li Lei
How to Normalize IPv4 Addresses and Avoid the Leading-Zero Trap
Strip leading zeros from IPv4 octets, get canonical dotted-decimal form, and stop inconsistent formatting from breaking your dedup and allowlists.
#ipv4#networking#data-cleanupRead more - · Li Lei
How to Deduplicate IP Addresses and Get a Clean List of Unique IPs
Leading-zero IPv4 variants like 010.0.0.1 survive a plain dedup and inflate your unique-IP count. Here is how to normalize first, then collapse an access log to one row per host.
#ipv4#deduplication#access-logsRead more - · Li Lei
IP to Decimal Explained: Turning 192.168.1.1 Into a Single 32-Bit Integer
How IP to decimal works: each IPv4 octet is an 8-bit chunk packed into one 32-bit number. Worked example, why databases store IPs as integers, and the reverse.
#ip to decimal#ip to integer#ipv4Read more - · Li Lei
How to Use an IP Subnet Calculator for CIDR Planning and VLSM
Use an IP subnet calculator to turn an IPv4 address and prefix into network, broadcast, usable range, host count and mask — and plan address space with VLSM.
#networking#subnetting#cidrRead more - · 李雷
How to Write an Invoice That Gets Paid: A Freelancer's Field Guide
What a real invoice needs — required fields, numbering, tax, and currency — plus how freelancers and small businesses can bill a client this afternoon with a local, private invoice generator.
#invoice#freelance#small-businessRead more - · Li Lei
Invisible Text and Blank Characters: How They Work and Where They Break
How invisible text and blank Unicode characters like U+3164 work, where to use them for empty messages and usernames, and which platforms strip them.
#invisible text#blank character#unicodeRead more - · Li Lei
Inventory Turnover, Explained: Ratio, COGS, and Days Sales of Inventory
How to calculate inventory turnover from COGS and average inventory, convert it to days sales of inventory, and read what a high or low number means.
#inventory turnover#retail#ecommerceRead more - · Li Lei
How to Use an Interview Questions Bank to Actually Prepare
Turn a 300+ interview questions bank into real prep: sort questions by category, answer behavioral ones with STAR, practice out loud, and tailor to the role.
#interview questions#behavioral interview#star methodRead more - · Li Lei
How to Use an Integral Calculator to Compute Definite and Indefinite Integrals
A practical walkthrough of integration with an integral calculator: the power rule, substitution, by parts, the constant of integration, and area under a curve.
#calculus#integrals#math toolsRead more - · Li Lei
Insulation R-Value Explained: Stack Layers, Hit Your Target
Understand what R-value measures, why higher means better, how stacked insulation layers add up, and the R-value your climate zone actually needs.
#insulation#r-value#building-scienceRead more - · Li Lei
What Inflation Really Costs You: Reading Past and Present Dollars Through CPI
A plain-English guide to how inflation erodes purchasing power over time, how to compare past and present dollars with CPI, and why compounding adds up fast.
#inflation#purchasing power#personal financeRead more - · Li Lei
Learn Indonesian Words Fast: 100 Essential Bahasa Indonesia Vocabulary for Beginners
A grounded guide to the 100 essential Indonesian words English speakers should learn first, why Bahasa Indonesia is so approachable, and how to drill it.
#indonesian#vocabulary#language-learningRead more - · Li Lei
How China Income Tax Brackets Really Work: Marginal vs Effective Rate
A plain-English guide to China's progressive income tax brackets, why a raise into a higher bracket never lowers your take-home pay, and how deductions cut your bill.
#income tax#tax brackets#personal financeRead more - · Li Lei
How to Watermark an Image: Add a Text or Logo Watermark That Survives Reposting
A practical guide to adding a text or logo watermark to your photos — opacity, the 9-position grid, diagonal tiling, batch runs, and why local processing keeps your originals private.
#image watermark#photo protection#watermark guideRead more - · Li Lei
How to Combine JPG and PNG Images Into One Ordered Image to PDF File
Turn a folder of JPG and PNG photos into a single ordered PDF, set page order and sizing, keep one image per page, and process private scans locally.
#image to pdf#jpg to pdf#png to pdfRead more - · Li Lei
Image to ASCII Art: How Brightness Becomes Characters
Turn any photo into ASCII art. Learn how brightness maps to characters, how output width changes detail, and why everything runs locally in your browser.
#ascii-art#image-conversion#text-artRead more - · Li Lei
How to Resize an Image to Exact Dimensions or by Percentage Without Stretching It
Resize an image to exact pixels or by percentage, lock the aspect ratio so nothing stretches, and learn why downscaling keeps quality while upscaling cannot.
#image-resizer#resize-image#aspect-ratioRead more - · Li Lei
Image Metadata Inspector: Read EXIF, IPTC, and XMP Like an EXIF Viewer
Read the hidden metadata in any image: EXIF camera settings, GPS, IPTC captions and copyright, and XMP edit history. A local EXIF viewer for review, forensics, and rights.
#image metadata#exif viewer#iptcRead more - · Li Lei
Free Image Hosting: Upload an Image and Get a Link You Can Paste Anywhere
How to upload an image and get a direct link for forums, Markdown and docs — and why a direct image link behaves differently from a page link.
#image hosting#direct image link#markdownRead more - · Li Lei
How to Convert Image Format Between PNG, JPG, and WebP (and When to Use Each)
A practical guide to converting images between PNG, JPG, and WebP — what each format is good at, why transparency disappears, and how to convert locally in your browser.
#image-format#png#jpgRead more - · Li Lei
What EXIF Metadata Hides in Your Photos (and How to Check Before You Post)
Photos quietly carry EXIF metadata like GPS coordinates, camera model, and timestamps. Here is how to scan and strip it locally before you share anything.
#exif#photo privacy#metadataRead more - · Li Lei
How to Crop an Image Online: Aspect Ratios, Avatars, and Privacy
A practical guide to cropping images online: lock aspect ratios like 1:1 and 16:9, frame perfect avatars and thumbnails, and keep every pixel in your browser.
#image-cropper#aspect-ratio#privacyRead more - · Li Lei
How to Compress an Image Without Losing Quality You Can See
A practical guide to compressing images: lossy vs lossless, the quality slider tradeoff, why smaller files speed up your site, and how to do it all locally.
#image compression#compress image#web performanceRead more - · Li Lei
How the IELTS Band Score Is Calculated: Rounding, Raw Scores, and the .25 Rule
Learn exactly how your IELTS overall band is averaged from four sections, why .25 rounds up to the next half band, and how Listening and Reading raw scores convert.
#ielts#test prep#studyRead more -
Why 0.1 + 0.2 ≠ 0.3: Reading the IEEE 754 Bits Behind the Most Famous Bug in Programming
Decode the actual sign, exponent, and mantissa bits that make 0.1 + 0.2 print 0.30000000000000004 — with real hex words you can verify yourself.
#ieee-754#floating-point#binaryRead more - · Li Lei
How to Build an ICS Calendar Event That Imports Into Any App
A practical guide to making an .ics calendar event with the right VEVENT fields, time zones, and all-day handling so it imports cleanly into any calendar app.
#ics#calendar#icalendarRead more - · Li Lei
How to Validate an IBAN: Country Code, Check Digits, and the mod-97 Test
How an IBAN is built from a country code, two check digits, and a national account number, and how the mod-97 test catches a typo before you wire money.
#iban#banking#validationRead more - · 李雷
HTTP Status Codes Explained: The Ones That Actually Bite in Production
A practical guide to HTTP status codes — what 2xx, 3xx, 4xx, and 5xx mean, the codes engineers confuse most (401 vs 403, 502 vs 504), and how to debug them fast.
#http status codes#debugging#backendRead more - · Li Lei
HTTP Status Codes by Class: What 200, 301, 404, 429, and 502 Actually Tell You
A practical guide to HTTP status codes by class. What 2xx, 3xx, 4xx, and 5xx mean, the codes you hit most, and how to read them while debugging an API.
#http#api#debuggingRead more - · Li Lei
The HTTP Security Headers Every Site Should Set (and How to Audit Them)
A practical walkthrough of HSTS, CSP, nosniff, frame-ancestors, Referrer-Policy, and Permissions-Policy, what each header defends against, and how to audit a response.
#security#http-headers#web-developmentRead more - · Li Lei
How to Read HTTP Headers: A Practical Field Guide to Request and Response Lines
Learn to read HTTP request and response headers by hand. What Content-Type, Cache-Control, Authorization, Set-Cookie, and CORS lines mean, plus how to debug an API from its headers.
#http#headers#apiRead more - · Li Lei
How to Normalize HTTP Headers Into One Canonical Form
Header names are case-insensitive, so Content-Type and content-type are the same field. Normalize a captured header set to canonical Train-Case before you compare or dedupe.
#http#headers#developer-toolsRead more - · Li Lei
How to Validate HTTP Headers and Clean a Header List
Check a list of HTTP headers for the Name: value shape, catch malformed lines, flag bad field-name characters, and export a clean header set, all in the browser.
#http#headers#validationRead more - · Li Lei
How to Extract HTTP Headers From a Raw Request or curl Dump
Pull every HTTP header out of a raw request, response, or curl -v dump into clean Key: Value pairs, locally in your browser, for docs, diffs, and debugging.
#http#headers#debuggingRead more - · Li Lei
How to Deduplicate HTTP Headers When Case Variants Hide Among Them
Content-Type and content-type are the same field, but a plain text dedup keeps both. Here is how to fold case variants and clean a captured header set.
#http#headers#deduplicationRead more - · Li Lei
How to Create a .htpasswd File for Apache and Nginx Basic Auth
Build a .htpasswd file for Apache or Nginx basic auth in your browser. Learn the user:hash format, when to pick bcrypt over apr1 or SHA-1, and how to wall off a staging site.
#htpasswd#basic auth#apacheRead more - · 李雷
HTML to Markdown: Convert Web Pages and Rich Text to Clean .md
A practical guide to converting HTML to Markdown — how tables, code blocks, and links are handled, why inline styles get dropped, and how to clean dirty CMS or Word HTML before you convert.
#html#markdown#converterRead more - · Li Lei
HTML to JSX: The Renames React Wants and How to Skip the Busywork
A practical guide to converting HTML to JSX for React — class to className, for to htmlFor, self-closing void tags, and turning inline style strings into objects.
#react#jsx#htmlRead more - · Li Lei
How to Convert an HTML Table to Markdown Without Hand-Fixing Rows
Copy a table off a web page and turn it into a clean GitHub-flavoured Markdown table: th becomes the header row, pipes get escaped, and cells flatten to text.
#html#markdown#tablesRead more - · Li Lei
How to Turn an HTML Table to CSV (and Open It Cleanly in Excel)
Copy a table off a web page and get clean CSV for Excel. How tr maps to rows, td to cells, why commas need quoting, plus a worked example.
#html#csv#excelRead more - · Li Lei
Build an HTML Table Without Hand-Coding a Single Tag
A practical guide to HTML table structure — table, thead, tbody, tr, th, td — plus scope for accessibility, styling basics, and pasting data straight from a spreadsheet.
#html#tables#accessibilityRead more - · Li Lei
How to Extract HTML Links and Build a Clean URL Inventory
Pull every anchor href, image, and script URL out of an HTML file, then dedup, split internal vs external, and turn the list into an SEO audit or sitemap.
#html#seo#linksRead more - · Li Lei
How to Format HTML: A Practical Guide to the HTML Formatter
Pretty-print minified or generated HTML into clean indented markup. How nesting, void tags, and inline elements format, all in your browser.
#html#formatting#web-developmentRead more - · Li Lei
Extract HTML Form Fields: Map Every Action, Method, and Input
Pull the structure out of any HTML form. List the action, method, and every field name, type, and required flag locally, without reading raw markup by hand.
#html#forms#frontendRead more - · Li Lei
Encoding HTML Entities: When < > & and " Must Be Escaped
A practical guide to HTML entity encoding and decoding: why <, >, &, and " need escaping, how named and numeric entities differ, and how they stop XSS.
#html#encoding#securityRead more - · Li Lei
Building an .htaccess File: Redirects, HTTPS, www, and Caching Without Breaking Your Site
A practical guide to writing Apache .htaccess rules — 301 redirects, force HTTPS, www canonicalization, caching, and custom error pages — with mod_rewrite basics.
#htaccess#apache#mod_rewriteRead more - · Li Lei
Quiz Yourself by HSK Level: A Chinese Vocabulary Quiz That Actually Tests Recall
How the HSK levels grade your Chinese, why an HSK vocabulary quiz with pinyin and tones beats passive reading, and how to use a Chinese vocabulary quiz to prep for the exam.
#chinese#hsk#vocabularyRead more - · Li Lei
How hreflang Tags Tell Google Which Language a Page Targets
A practical guide to hreflang tags for multilingual and multi-region sites: return-tag rules, x-default, avoiding duplicate content, and a worked example.
#hreflang#international seo#multilingualRead more - · Li Lei
Horsepower vs Torque, and Why They Cross at 5252 RPM
How horsepower, torque and RPM relate, why HP equals torque at 5252 RPM, what each tells you about a car's feel, and how to solve any one from the other two.
#horsepower#torque#rpmRead more - · Li Lei
Hooke's Law Explained: F = kx, Spring Constants, and the Elastic Limit
A practical guide to Hooke's law, F = kx. Solve for spring force, spring constant, or displacement, find elastic energy, and respect the elastic limit.
#physics#hookes-law#springsRead more - · Li Lei
How Much House You Can Afford: The 28/36 Rule, Down Payment, and Debt
Work out how much house you can afford with the 28/36 rule. See how down payment and debt move your number, and why a lender's max is not your real budget.
#home affordability#28/36 rule#mortgageRead more - · Li Lei
HMAC Explained: How a Shared Secret Proves a Webhook Is Real
How HMAC mixes a secret key into a hash like SHA-256 to prove message integrity and authenticity, why it beats a plain hash, and how to verify Stripe and GitHub webhooks locally.
#hmac#webhooks#securityRead more - · Li Lei
The 100 Hindi Words That Carry You: Learn Hindi Words That Actually Get Used
Start Hindi vocabulary the honest way — the most useful core words in Devanagari, with gender, postpositions, and loanwords explained for English speakers.
#hindi#vocabulary#language-learningRead more - · Li Lei
How to Read a Hex Dump: Offset, Hex Bytes and the ASCII Gutter
Learn to read a hex dump column by column, spot file magic numbers like 25 50 44 46, and understand why the ASCII gutter makes binary inspection fast.
#hex#binary#encodingRead more - · Li Lei
How to Convert a Hex Color List into JSON, CSS Variables, and a TypeScript Union
Turn a plain list of hex colors into a JSON palette array, CSS custom properties, a TypeScript union, or a Markdown swatch table for clean design tokens.
#hex colors#design tokens#color paletteRead more - · Li Lei
The Henderson-Hasselbalch Equation: Buffer pH from pKa and the Conjugate Base Ratio
How the Henderson-Hasselbalch equation links buffer pH, pKa, and the conjugate base/acid ratio, with a worked example where equal amounts give pH = pKa.
#chemistry#buffers#biochemistryRead more - · Li Lei
Heat Index Explained: Why 90°F Can Feel Like 105°F
How the heat index turns air temperature and humidity into a real feels-like number, why humid heat is dangerous, and what the NWS risk bands mean.
#heat index#feels like temperature#weather safetyRead more - · Li Lei
Hat Size Explained: Head Circumference to US, UK and S/M/L
Measure your head once and read every hat size from it. How US, UK, EU, and S/M/L sizes relate, with a worked example and the math behind the numbers.
#hat size#head circumference#sizing guideRead more - · Li Lei
How to Normalize Hashtags Into One Canonical Form
A practical guide to normalizing hashtags: one leading #, consistent lowercase, no stray spaces or punctuation, so a campaign tag list dedupes cleanly.
#hashtags#social media#data cleanupRead more - · Li Lei
How to Validate a Hashtag List Before You Schedule a Campaign
Validate hashtags from a pasted list or text file: one leading #, letters, digits, and underscores only. Catch broken tags and clean the set before you post.
#hashtags#social media#validationRead more - · Li Lei
How to Convert a Hashtag List Into a Caption String, CSV, and JSON
Turn a column of hashtags into a space-joined caption line, CSV, JSON array, Markdown, SQL IN, or a TypeScript union, all in one local step for social posts and campaign sheets.
#hashtags#social-media#marketingRead more - · 李雷
How Many Hashtags to Use on Each Platform (Instagram, TikTok, X)
A platform-by-platform hashtag guide: how many to use on Instagram, TikTok and X, relevance vs. trend size, how to pick them, and how to avoid getting throttled.
#hashtags#instagram#tiktokRead more - · Li Lei
How to Extract Hashtags From Any Text and Build a Reusable Tag Library
Pull every hashtag out of pasted posts, exports, or notes, then dedupe, count, and reuse them. A practical workflow for social media managers building a clean tag library.
#hashtag-extractor#social-media#content-workflowRead more - · Li Lei
How to Deduplicate Hashtags and Keep One Clean List of Unique Hashtags
Case variants and missing-# copies make the same tag survive a plain dedup. Here is how to collapse a campaign hashtag list down to truly unique tags.
#hashtags#social media#text cleanupRead more - · Li Lei
How to Read a HAR File and Find What Slows a Page Down
A practical guide to analyzing a HAR file from browser devtools: find the slowest requests, biggest payloads, and render-blocking resources, all locally.
#web performance#HAR file#devtoolsRead more - · Li Lei
Is It a Happy Number? The Sum-of-Squares Rule, Explained
How a happy number works: square each digit, add them up, repeat. Reach 1 and it is happy; fall into the 4-cycle and it is not. With a worked example and code notes.
#happy number#recreational math#cycle detectionRead more - · Li Lei
How to Make a Printable Handwriting Practice Sheet That Actually Helps
A practical guide to printable handwriting practice sheets — the four guide lines, tracing vs blank cells, and custom words for kids learning letters or adults practicing cursive.
#handwriting#practice sheet#printableRead more - · Li Lei
How to Compute Hamming Distance: Count the Positions That Differ
A plain-English guide to Hamming distance: count differing positions in equal-length strings, XOR-and-count for binary, real uses, and how it differs from edit distance.
#hamming-distance#bit-manipulation#error-correcting-codesRead more - · Li Lei
Hamming Code Explained: Encoding, Syndromes, and Fixing One Flipped Bit
How a Hamming code places parity bits at power-of-two positions, computes a syndrome to locate a single-bit error, and corrects it without retransmission.
#hamming-code#error-correction#parityRead more - · Li Lei
How Half-Life Works: Radioactive Decay, Carbon Dating, and Drug Clearance Explained
A plain-English guide to half-life: the N=N0*(1/2)^(t/T) decay formula, the decay constant, mean lifetime, carbon dating, and drug elimination, with worked examples.
#half-life#radioactive decay#exponential decayRead more - · Li Lei
How to Check a Haiku's 5-7-5 Syllable Structure
A practical guide to checking a haiku's 5-7-5 syllables, the form's history and season-word tradition, why English counting is approximate, and how to write a tight haiku.
#haiku#writing#poetryRead more - · Li Lei
Gray Code Explained: One Bit at a Time, From Binary and Back
How Gray code keeps a single bit changing between neighbours, the gray = n XOR (n>>1) formula, a worked decimal example, and why rotary encoders depend on it.
#gray-code#binary#encodersRead more - · Li Lei
How Much Gravel Do I Need? A Driveway and Path Estimating Guide
Estimate gravel for a driveway or path by volume and weight. Learn depth rules, how to convert cubic yards to tons by density, and how to order without running short.
#gravel#driveway#landscapingRead more - · Li Lei
How Much Grass Seed Do You Actually Need? A Seeding Rate Guide
Work out how much grass seed your lawn needs from area and seeding rate, why new lawns need double the overseeding rate, and how species and timing change the math.
#grass seed#lawn care#seeding rateRead more - · Li Lei
How a GraphQL Formatter Turns a Minified Query Back Into Readable Code
A practical look at formatting GraphQL queries and schemas: consistent selection-set indentation, reading a minified query, and processing everything locally in your browser.
#graphql#formatting#developer-toolsRead more - · Li Lei
Graph Paper, Your Way: Square, Dot, Isometric and Log Grids You Can Actually Print
How to make printable graph paper in square, dot, isometric and log grids, pick the right spacing and page size, and print it true to scale.
#graph paper#printable templates#grid designRead more - · 李雷
Grade Calculator Guide: Weighted Scores, Final Exam Targets, and Letter Grades
How a grade calculator turns weighted homework, quizzes, and exams into one course grade, finds the final score you need for a target, and maps it to a letter.
#grade calculator#weighted grade#final examRead more - · 李雷
How GPA Works: The 4.0 Scale, Weighted vs Unweighted, and Letter-to-Point Math
A practical guide to GPA on the 4.0 scale: how weighted and unweighted averages differ, how credit hours change your number, and how A/B/C letters map to grade points.
#gpa#4.0 scale#weighted gpaRead more - · Li Lei
How a Golf Handicap Index Actually Works
A plain-English walk through the golf handicap index: score differentials, course and slope rating, averaging your best recent rounds, and net scoring for fair matches.
#golf#handicap#world handicap systemRead more - · Li Lei
Glove Size Explained: Measure Your Hand and Read Every Scale
Learn how glove size works, how to measure hand circumference around the palm, and how one number maps to S/M/L and EU sizes for work and sports gloves.
#glove size#hand measurement#sizing guideRead more - · 李雷
How to Add a README Badge: The Complete shields.io-Style Guide
Learn what a README badge is, how shields.io styles work, the common build, version, license, and downloads badges, and exactly how to paste badge markdown into your README.
#github#readme#badgeRead more - · Li Lei
The First 100 German Words That Make German Vocabulary Click
Learn German words that actually matter: the most frequent ~100, the three genders der/die/das, cases, compound words, and English cognates that speed you up.
#german#vocabulary#language learningRead more - · Li Lei
How Geohash Turns a Lat/Long Into a Short String You Can Search By Prefix
A practical look at geohash: how each character shrinks the bounding box, why nearby points share a prefix, and how to pick precision against length.
#geohash#geospatial#encodingRead more - · Li Lei
Gear Ratio Explained: Driven Teeth Over Drive Teeth, and the Speed-for-Torque Trade
Gear ratio is driven teeth divided by drive teeth. Learn how it trades speed for torque on bikes, cars and machines, plus how to read multi-stage ratios.
#gear ratio#mechanical#cyclingRead more - · Li Lei
GC Content of a DNA Sequence: What the G+C Percentage Tells You
How to compute GC content of a DNA sequence, why the G+C percentage controls melting temperature and duplex stability, and how it guides PCR primer design.
#bioinformatics#dna#pcrRead more - · Li Lei
How to Play and Win the 2048 Game: The Merge Math and Corner Strategy
A practical guide to the 2048 game: how the merge mechanic doubles equal tiles, why every move spawns a new tile, and the corner strategy that gets you to 2048 and past it.
#2048 game#puzzle strategy#tile mergingRead more - · Li Lei
Future Value of Money: How Compound Interest, Contributions, and Time Build Wealth
A plain-English walkthrough of future value: the compound interest formula, lump sum versus regular contributions, and why an early start beats a bigger one.
#finance#compound interest#future valueRead more - · 李雷
Fuel Cost for Any Trip: Distance, MPG, and Pump Price Made Simple
Turn distance, fuel economy, and pump price into one real fuel cost. Convert MPG to L/100km, handle US vs UK gallons, and split a carpool fairly to the cent.
#fuel cost#fuel economy#road tripRead more - · Li Lei
MPG to L/100km: How to Read Fuel Economy in Any Unit
Convert MPG to L/100km and back, tell US from UK gallons, and understand why fuel economy is inverse not linear — with worked numbers for car buying.
#fuel economy#mpg#l/100kmRead more - · Li Lei
Frequency and Wavelength: The One Equation That Ties Them Together
How frequency and wavelength relate through λ = v/f, with worked radio, light, and sound examples plus a quick antenna sizing method you can trust.
#frequency wavelength#wave physics#radioRead more - · Li Lei
The First 100 French Vocabulary Words: A Faster Way to Learn French Words
Start French with the 100 most useful words. Why high-frequency vocabulary speeds up comprehension, plus how to handle gender, liaison, and silent letters.
#french vocabulary#learn french words#delf a1Read more - · Li Lei
How to Set a Freelance Hourly Rate That Actually Pays You
Set a freelance hourly rate from a target salary plus expenses, billable hours, and taxes. Why your contractor rate must beat any employee wage.
#freelance#hourly rate#pricingRead more - · Li Lei
Free Fall, Explained: The Distance and Velocity Equations That Actually Work
How free fall works under gravity: the distance and velocity equations, a worked 3-second drop, and why air resistance breaks the textbook answer.
#physics#kinematics#free fallRead more - · Li Lei
The Digital Fortune Cookie: A Daily Message You Actually Open
A random digital fortune cookie for a daily nudge or party icebreaker, the surprising California history, and why one short line can feel personal.
#fortune cookie#daily fortune#icebreakerRead more - · Li Lei
Font File Inspector: Read Font Metadata Before You Ship a Typeface
A practical guide to inspecting TTF, OTF, WOFF, and WOFF2 files, reading font metadata like family, version, glyph count, character coverage, and embedding flags, all locally.
#fonts#typography#web-developmentRead more - · Li Lei
How Much Flooring to Buy: A Box-Counting Guide for Laminate, Hardwood, and Vinyl
Stop guessing how many boxes of flooring you need. A practical method for laminate, hardwood, and vinyl: room area, box coverage, the right waste percentage, and a worked example.
#flooring#home improvement#diyRead more - · Li Lei
Aquarium Water Volume: How to Calculate Real Fish Tank Gallons and Liters
Calculate aquarium water volume in gallons and liters with the length x width x height formula, why real volume runs lower than tank size, and the inch-per-gallon stocking rule.
#aquarium#fish tank#calculatorRead more - · Li Lei
How to Find Which Fiscal Year and Quarter Any Date Falls In
A plain guide to fiscal years versus calendar years, why fiscal year-ends differ, and how to map any date to its fiscal year and quarter.
#fiscal year#finance#accountingRead more - · Li Lei
How to Measure a Firewood Cord and Never Get Shortchanged
A plain-English guide to measuring firewood by the cord — what 128 cubic feet means, how a full cord differs from a face cord, and how to check a delivery.
#firewood#firewood cord#measurementRead more - · Li Lei
What You Need on the Final Exam to Hit Your Target Final Grade
Work out the exact score you need on the final exam to reach a target grade — the formula, a worked example, and how to spot when a target is impossible.
#final grade calculator#final exam#study planningRead more - · Li Lei
How to Sanitize a Filename: Make Any String a Safe Filename Everywhere
Learn the forbidden characters, reserved names, and trailing-dot traps that break filenames, and how to sanitize any string into a safe filename across Windows, macOS, and Linux.
#filename#cross-platform#developer-toolsRead more - · Li Lei
Encoding a File to Base64: Data URIs, Inline Assets, and the 33% Tax
How to encode any file to Base64 or a data URI, embed small assets inline, ship binary through JSON and email, and why the output grows about a third.
#base64#encoding#data-uriRead more - · Li Lei
Reading a File's Real Type From Its Magic Bytes, Not Its Extension
A renamed .jpg can really be a PNG or worse. Learn how magic bytes reveal a file's true type, why it matters for upload security, and how to inspect files locally.
#file types#magic bytes#mime typeRead more - · Li Lei
Computing File Hashes with MD5, SHA-1, and SHA-256: A Practical Guide
How to compute file hashes, verify downloads against published checksums, and spot tampering with SHA-256. Runs locally in your browser, no upload.
#file hash#checksum#sha256Read more - · Li Lei
How to Verify a File Hash: Compare a Checksum Before You Trust a Download
A practical guide to verifying downloads with a checksum. Compare the computed SHA-256 or MD5 against the publisher's value, and learn what a match really proves.
#checksum#sha256#file integrityRead more - · Li Lei
How to Estimate Fence Materials: Posts, Rails, Pickets, and Budget
Turn a fence length and post spacing into an exact materials list — posts, rails, pickets, and gate allowance — so you buy once and skip the second store trip.
#fence#home improvement#estimatingRead more - · 李雷
Favicon Sizes Explained: 16, 32, 180, 192, and 512 px Done Right
A practical guide to favicon sizes for every platform — browser tabs, iOS apple-touch-icon, Android Chrome, and PWA manifests — with the exact HTML link tags to paste into your head.
#favicon#web-development#htmlRead more - · Li Lei
How a Fancy Text Generator Turns Plain Words Into Unicode Styles
A practical guide to making bold, italic, script, and bubble fancy text for bios and posts — why it is real Unicode, where it pastes, and the screen-reader caveats.
#fancy text#unicode#social mediaRead more - · Li Lei
Exposure Value Explained: How Aperture and Shutter Combine Into One EV Number
A working photographer's guide to exposure value (EV): the log2 formula, stops, reciprocal settings that share one EV, and using EV to nail exposure in tricky light.
#photography#exposure#exposure valueRead more - · Li Lei
How to Track Spending with a Private Expense Tracker (and Actually Change Your Habits)
Track spending by category, apply the 50/30/20 rule, and spot budget leaks with a free expense tracker that keeps your financial data local to your browser.
#personal finance#budgeting#expense trackerRead more - · Li Lei
Expected Value Explained: the Math Behind Smart Bets and Big Decisions
Expected value is the probability-weighted average of outcomes. Learn the formula, work a dice example, and see why a positive EV bet can still lose short-term.
#expected value#probability#decision makingRead more - · Li Lei
Excel Column Letter to Number: How the A=1, Z=26, AA=27 System Really Works
Excel columns count in bijective base-26: A is 1, Z is 26, AA is 27, with no zero digit. Here is the math, a worked example, and why macros need it.
#excel#spreadsheets#base-26Read more - · Li Lei
How Much Does It Cost to Charge an Electric Car? The EV Charging Cost Math
Work out EV charging cost from battery kWh and your electricity rate, factor in ~10% charging losses, get cost per mile, and compare home vs public charging and petrol.
#ev#electric vehicles#charging costRead more - · Li Lei
Escape Velocity Explained: Why You Need 11.2 km/s to Leave Earth
How escape velocity works with v = √(2GM/r), why Earth needs 11.2 km/s, how the Moon, Mars and black holes compare, and how it differs from orbital speed.
#escape velocity#physics#spaceRead more - · Li Lei
How an English Vocabulary Quiz Tests and Builds Your Word Knowledge
A practical guide to using an English vocabulary test to measure your word knowledge, why active recall beats rereading lists, and how to study the words you miss.
#english vocabulary#vocabulary test#active recallRead more - · Li Lei
English Irregular Verbs: The Three Forms, Common Patterns, and the Ones Learners Get Wrong
A study reference for English irregular verbs — the base, past, and past participle forms, the rhyming patterns like go-went-gone, and the traps to avoid.
#english grammar#irregular verbs#past tenseRead more - · Li Lei
The English Grammar Rules People Look Up Most (and the Mistakes That Follow)
A quick reference to the English grammar rules learners and writers search for most: subject-verb agreement, a/an/the, tense, commas, who/whom, its/it's.
#english grammar rules#grammar reference#english tensesRead more - · Li Lei
Why Native Speakers Make a Decision but Never Do One: A Guide to English Collocations
Collocations are the word pairings native speakers say without thinking. Learn the common types, why they make you sound fluent, and how to look them up.
#english collocations#english learning#vocabularyRead more - · Li Lei
Engineering Notation Explained: Why 4700 Ohms Reads as 4.7k
How engineering notation locks exponents to multiples of three so 4700 ohms becomes 4.7k, how it differs from scientific notation, and how to read electronics markings.
#engineering notation#si prefixes#electronicsRead more - · Li Lei
Emoji to Unicode: Reading the Code Points Behind Every Glyph
How an emoji maps to U+XXXX code points, why some sit above U+FFFF and need surrogate pairs, the \u and U+ formats, and how ZWJ joins several into one glyph.
#emoji#unicode#code-pointsRead more - · Li Lei
How to Remove Emoji From Text Cleanly Without Breaking Your Data
Remove emoji and pictographs from text without touching your words. How emoji live in Unicode blocks, why family and flag emoji break naive tools, and a clean fix.
#emoji#text#unicodeRead more - · Li Lei
How to Suggest Emoji for Any Sentence with an Emoji Recommender
An emoji recommender reads your sentence and suggests emoji that match its keywords and sentiment, so you stop scrolling the picker. Here is how it works and where to use it.
#emoji#writing#social mediaRead more - · Li Lei
Emoji Combos Without the Stickers: How an Emoji Kitchen Builds Copyable Unicode
How an emoji kitchen combines and arranges emoji into a plain Unicode string you copy as text — pastes anywhere, renders per-platform, no image files.
#emoji#unicode#textRead more - · Li Lei
How to Search Emoji by Meaning and Copy Them Anywhere with an Emoji Finder
An emoji finder lets you search emoji by name or feeling, copy the character with one click, and paste it anywhere — because every emoji is a Unicode code point.
#emoji#unicode#productivityRead more - · Li Lei
How to Build a Professional Email Signature That Survives Gmail and Outlook
A practical guide to building a professional email signature: what to include, why HTML signatures use inline-styled tables, and how to install one in Gmail and Outlook.
#email signature#html email#productivityRead more - · Li Lei
Email Obfuscation: How to Hide Your Email From Scraper Bots
Hide your email from harvesting bots with HTML entities, JavaScript link assembly, CSS reversal, and [at]/[dot] text. Practical tradeoffs and a worked example.
#email obfuscation#hide email#anti-spamRead more - · Li Lei
How to Normalize Email Addresses Into One Canonical Form
Learn how to normalize email addresses by trimming whitespace, removing wrappers, and lowercasing, so equivalent entries collapse to one canonical string for dedup and matching.
#email#data-cleaning#normalizationRead more - · Li Lei
How to Validate Email Addresses and Clean a Mailing List
Validate a list of email addresses by syntax, see why each row failed, and learn why a syntax-valid address still bounces. A first-pass filter, not a deliverability check.
#email#validation#data-cleaningRead more - · Li Lei
How to Deduplicate Emails: Remove Duplicate Emails the Smart Way
A plain-text dedup misses case differences and Gmail aliases. Here is how to remove duplicate emails by the inbox they actually reach, all in your browser.
#email#data-cleaning#mailing-listRead more - · 李雷
How to Calculate Electricity Cost: Watts to kWh to Money
Turn appliance wattage into a real electricity cost — convert watts to kWh, work out cost per day, month, and year, find your power hogs, and price standby drain.
#electricity cost#energy#kwhRead more - · Li Lei
Egyptian Fractions Explained: Writing 5/6 as a Sum of Unit Fractions
How the ancient Egyptians wrote every fraction as a sum of distinct unit fractions, how the greedy algorithm builds the expansion, and how to compute it instantly.
#egyptian fractions#unit fractions#math historyRead more - · Li Lei
How EditorConfig Ends the Tabs-vs-Spaces War on Your Team
A practical guide to the .editorconfig file: root=true, indent style and size, end-of-line, charset, and per-filetype overrides that every editor applies automatically.
#editorconfig#code style#developer toolsRead more - · Li Lei
Learn Dutch Words Fast: The Core Dutch Vocabulary an English Speaker Already Half-Knows
A practical guide to the first 100 essential Dutch words for English speakers — cognates, the de/het genders, the throaty g, and how to drill core Dutch vocabulary.
#dutch#vocabulary#language-learningRead more - · Li Lei
From Raw Seconds to Human Readable Duration: 3661s Becomes 1h 1m 1s
Turn raw seconds and milliseconds into readable durations like 1h 1m 1s. The divide-by-60-60-24 math, a worked 90061s example, and where it matters.
#duration#time-format#developer-toolsRead more - · Li Lei
Converting Time Units: Seconds, Minutes, Hours, Days, and Milliseconds
How to convert between seconds, minutes, hours, days, and weeks, turn a big timeout or uptime count into human terms, and reach milliseconds for code.
#duration#time units#seconds to minutesRead more - · Li Lei
How to Find Duplicate Files by Content Hash (Not Filename)
Find duplicate files by content hash, not by name. Learn why SHA matching beats filenames and how to clean a drive or photo library locally.
#duplicate files#file management#hashingRead more - · Li Lei
How Many Drywall Sheets a Room Needs: A Calculator Walkthrough
Work out drywall sheets from wall plus ceiling area, pick 4x8 or 4x12 boards, add a waste margin, and size joint compound and screws — with a worked room example.
#drywall#renovation#calculatorRead more - · Li Lei
Drill Bit Size Decoded: Fraction, Number, Letter and mm Made Simple
Drill bits come in four numbering systems on one scale. Learn to convert between fraction, number, letter and mm and pick the right pilot or tap drill.
#drill bits#tap drill#measurementRead more - · 李雷
Dream Meaning Decoded: Two Ways to Read Falling Teeth, Being Chased, and Flying
What does your dream mean? A practical guide to reading common dream symbols through both Zhougong folk tradition and Jungian psychology, with cultural context and a level-headed take.
#dream interpretation#dream meaning#dream symbolsRead more - · Li Lei
How to Estimate Download Time Without Getting Burned by Bits vs Bytes
Estimate download time from file size and connection speed, dodge the Mbps vs MB/s trap, and add the real-world overhead that makes the number honest.
#download time#bandwidth#file transferRead more - · Li Lei
How to Normalize Domain Names So Your Lists Dedupe Correctly
Normalize domain names by lowercasing, stripping protocol, www, path, port, and trailing dots, plus IDN punycode folding so analytics and allowlists dedupe right.
#domains#data-cleanup#seoRead more - · Li Lei
How to Validate Domain Names in a Pasted List Without Guesswork
Validate a domain list against real label rules, catch malformed entries with a reason on every row, and learn why syntax-valid never means registered.
#domains#validation#text-toolsRead more - · Li Lei
Convert a Domain List into JSON, SQL IN, CSV, and TypeScript Union Output
Turn a plain list of domain names into a JSON allowlist array, a SQL IN clause, CSV, or a TypeScript union in one step, no hand-quoting each host.
#domains#developer-tools#converterRead more - · Li Lei
How to Extract Domain Names From Messy Text, URLs, and Emails
Pull clean, registrable domain names out of pasted text, full URLs, and email addresses, then dedupe and export the list. Everything runs locally in your browser.
#domains#text-processing#data-cleanupRead more - · Li Lei
How to Deduplicate Domains and Keep One Clean Copy of Every Unique Domain
Case, www, protocol wrapping, and trailing dots make one site survive a plain dedup as several rows. Here is how to collapse a domain list into unique domains.
#domains#deduplication#data-cleanupRead more - · Li Lei
How to Normalize DOIs to One Canonical Form Before You Dedupe a Bibliography
Strip the doi.org resolver prefix, drop the doi: scheme, lowercase the registrant, and reduce every reference to a bare 10.xxxx/suffix so duplicates finally string-match.
#doi#bibliography#reference-managementRead more - · Li Lei
How to Validate DOIs and Clean a DOI List Before You Cite It
Validate DOIs against the 10.registrant/suffix syntax, flag entries missing the 10. prefix or slash, and clean a bibliography locally in your browser.
#DOI#bibliography#reference-managementRead more - · Li Lei
How to Extract DOIs From Messy References and Pasted Text
A practical guide to pulling Digital Object Identifiers out of reference lists, PDFs, and notes, then deduping them into a clean citation list locally.
#doi#citations#researchRead more - · Li Lei
How to Deduplicate DOIs Without Letting Prefix and Case Variants Slip Through
A plain text dedup keeps duplicate DOIs because the resolver prefix and letter case differ. Here is how to collapse those variants into one clean citation.
#doi#citations#deduplicationRead more - · Li Lei
How a Dog Breed Finder Matches the Right Breed to Your Actual Life
A practical guide to matching a dog breed to your lifestyle — size, energy, grooming, apartment fit, kids and allergies — and why temperament beats looks.
#dog breeds#pet ownership#lifestyleRead more - · Li Lei
DNA to RNA: How Transcription Turns a Coding Strand into mRNA
Transcribe a DNA sequence to mRNA the right way: swap T for U, tell the coding strand from the template, and read everything 5' to 3' with a worked example.
#biology#bioinformatics#geneticsRead more - · Li Lei
Dividend Yield Explained: Reading Income Stocks Without Getting Burned
How dividend yield works, why a very high yield is often a warning, and how yield on cost turns a 3% buy into a 5%+ payout over time.
#dividend yield#income investing#dividend growthRead more - · 李雷
How a Discount Calculator Gets Stacked Coupons and Tax Right
Learn how percent-off math works, why stacked 20%+10% coupons never equal 30% off, and how to find your real after-tax final price with a discount calculator.
#discount calculator#percent off#stacked discountsRead more - · 李雷
How to Build a Clean ASCII Directory Tree for Your README
Build an ASCII directory tree for your README or docs from an indented file list. Compare the unix tree command, learn the box-drawing connectors, and generate one fast.
#directory tree#readme#asciiRead more - · Li Lei
The Dilution Equation: How to Find Stock and Water Amounts with C1V1 = C2V2
Use the C1V1 = C2V2 dilution equation to find exactly how much stock and how much water to mix for lab, aquarium, and cleaning solutions.
#dilution#chemistry#labRead more - · Li Lei
How a Diceware Passphrase Beats Your Short Complex Password
Why six random words make a stronger, more memorable password than a short complex one — entropy per word, a worked example, and fully local generation.
#security#passwords#passphraseRead more - · Li Lei
Dice Roller for D&D: Notation, Fairness, and Modifiers Explained
How a virtual dice roller handles D&D notation like 3d6+2, why digital randomness can be fairer than physical dice, and how modifiers and advantage actually work.
#dice roller#dnd#tabletopRead more - · Li Lei
Dice Probability Explained: Why 7 Wins and How Dice Odds Really Work
A plain guide to dice probability and dice odds: the 36 outcomes of two dice, why 7 is most likely, the bell curve, and at-least vs exactly chances.
#dice probability#dice odds#tabletopRead more - · Li Lei
Why Dew Point Beats Relative Humidity for the Muggy Feel
Dew point is the temperature air must cool to for saturation. Here is why it predicts the sticky feel better than relative humidity, plus a worked example.
#dew point#humidity#weatherRead more - · Li Lei
Depth of Field Explained: How Aperture, Focal Length and Distance Set Your Sharp Zone
How aperture, focal length, and subject distance control depth of field, plus hyperfocal distance for landscapes and shallow portrait backgrounds.
#photography#depth of field#hyperfocal distanceRead more - · 李雷
Depreciation, Three Ways: Straight-Line vs. Declining Balance vs. Sum-of-Years-Digits
How the three textbook depreciation methods build a year-by-year schedule, when to use each, and a worked example showing a $25,000 van written down to its salvage value.
#depreciation#accounting#financeRead more - · Li Lei
Density Made Simple: Mass, Volume, and Why Things Float
Understand density as mass over volume, solve for any of the three, learn why objects float against water at 1 g/cm³, and handle unit conversions cleanly.
#density#physics#calculatorRead more - · Li Lei
Delta E Explained: Measuring Color Difference for Print and Screen
A practical guide to Delta E (ΔE) color difference: what the number means, CIE76 vs CIEDE2000, a worked Lab example, and how to hold brand colors to tolerance.
#delta-e#color-difference#ciede2000Read more - · Li Lei
How a Decibel Adds Up: Logarithms, +3 dB, and Safe Noise
Why decibels never add arithmetically. How +10 dB means 10x power, +3 dB means double, why two 60 dB sources combine to 63 dB, and safe noise limits.
#decibels#acoustics#noiseRead more - · Li Lei
The Debt-to-Income Ratio Lenders Use: A Practical DTI Guide
How mortgage lenders read your debt-to-income ratio, the difference between front-end and back-end DTI, the 28/36 and 43 percent thresholds, and how to lower yours.
#debt-to-income#dti#mortgageRead more - · Li Lei
Debt Payoff Planning: Avalanche vs Snowball and What an Extra $200 Saves
How the avalanche and snowball methods differ, why extra payments cut years of interest, and how to read a month-by-month debt payoff schedule.
#debt payoff#personal finance#debt snowballRead more - · Li Lei
What Day of the Week Was Any Date? How to Find the Weekday Fast
Find the weekday for any date, past or future. What day you were born, when an anniversary lands, and how Zeller and Doomsday math figure it out by hand.
#date#calendar#weekdayRead more - · Li Lei
How to Calculate the Date Difference: Days Between Dates Done Right
A practical guide to counting days between dates, business days vs calendar days, inclusive vs exclusive counting, and how to avoid the classic off-by-one mistake.
#date-difference#days-between-dates#business-daysRead more - · Li Lei
Mbps vs MB/s: Reading Your Real Data Transfer Rate
Why a 100 Mbps plan downloads at 12.5 MB/s, how to convert bps, Kbps, Mbps and Gbps to bytes per second, and the 8-bits-per-byte trap that trips everyone up.
#bandwidth#networking#data transfer rateRead more - · Li Lei
Bytes, KB, MB, GB, TB: Why Data Storage Units Never Quite Add Up
A plain guide to data storage units — bytes, KB, MB, GB, TB — and the 1000 vs 1024 split (decimal SI vs binary IEC, KiB/MiB) that makes a 1 TB drive read as 931 GiB.
#data storage#bytes#unit conversionRead more - · Li Lei
FTP for Cyclists: The 20-Minute Test, Power Zones, and W/kg Explained
Estimate cycling FTP from a 20-minute test (×0.95), build the seven Coggan power zones in watts, and read your watts per kilogram with a worked example.
#cycling#ftp#power trainingRead more - · Li Lei
Customer Lifetime Value (LTV) Explained: The Formula and the LTV:CAC Ceiling
How to calculate customer lifetime value with the simple and SaaS formulas, why the LTV:CAC ratio matters, and how LTV caps your acquisition spend.
#customer lifetime value#ltv#clvRead more - · Li Lei
Currency Converter Guide: How Exchange Rates Work and Why the Rate You Get Isn't the Headline Rate
A plain-English guide to using a currency converter, how exchange rates are set, the gap between the mid-market rate and what your bank actually pays, and why rates move.
#currency converter#exchange rate#foreign exchangeRead more - · 李雷
curl to Code: Convert curl Commands into Python, JavaScript, and Go
Turn any curl command into idiomatic Python requests, JS fetch, or Go net/http. Copy curl from DevTools, handle headers and JSON bodies, and paste working code.
#curl#http#pythonRead more - · Li Lei
Testing APIs with curl: The curl Commands and Flags You Actually Use
A practical curl cheat sheet for testing APIs: sending JSON, headers, auth, following redirects, downloading files, and debugging requests with -v and -i.
#curl#api-testing#httpRead more - · Li Lei
How to Transpose CSV Data: Flip Rows and Columns Without a Spreadsheet
A practical guide to transposing CSV files: swap rows and columns, reshape wide tables for readability, the Excel transpose shortcut, and prepping data for pivots.
#csv#data#spreadsheetRead more - · Li Lei
CSV to YAML: Turn a Spreadsheet Export Into a Clean Object Array
Convert CSV to YAML the right way: header row becomes keys, each data row becomes an object, and type inference keeps your numbers, booleans and nulls real.
#csv to yaml#yaml#converterRead more - · Li Lei
CSV to XML: Map Every Row to a Record Element the Right Way
A practical guide to converting CSV to XML — each row a record element, columns as child tags or attributes, custom root and row names, and safe escaping for legacy and SOAP imports.
#csv to xml#xml#data conversionRead more - · Li Lei
CSV to TSV: When Tabs Beat Commas, and How to Convert Safely
A practical guide to converting CSV to TSV, why tab-delimited data survives commas in your fields, and how quoting and escaping should be handled.
#csv#tsv#dataRead more - · 李雷
CSV to SQL: Generate Type-Inferred INSERT Statements Safely
A practical guide to converting CSV to SQL — type inference, single-quote escaping against injection, batched vs per-row INSERTs, and bulk imports into MySQL, PostgreSQL, and SQLite.
#csv#sql#databaseRead more - · Li Lei
How to Convert a CSV to Markdown Table for GitHub and Docs
Convert a CSV to Markdown table for GitHub READMEs, issues, and docs. Learn the header separator row, column alignment, and how to escape pipes safely.
#csv#markdown#githubRead more - · Li Lei
How to Convert a CSV to a LaTeX Table for Academic Papers
Turn CSV data into a compile-ready LaTeX table: build the tabular environment, set column alignment, use booktabs rules, and escape special characters safely.
#latex#csv#academic-writingRead more - · Li Lei
How to Convert CSV to HTML Table Without Hand-Typing Tags
Turn a CSV export into a clean HTML table: first row to thead, data rows to tbody, special characters escaped, ready to paste into pages, blogs, and email.
#csv#html#converterRead more - · Li Lei
A Fast CSV Statistics Summary for Sanity-Checking Exported Data
Get a quick CSV summary with count, min, max, mean, median, and sum per numeric column. Spot outliers and nulls in seconds, locally, without a spreadsheet.
#csv#data-quality#statisticsRead more - · Li Lei
How to Sort CSV Files by Column Without a Spreadsheet
Sort CSV rows by any column, ascending or descending, with numeric-aware ordering, multi-column passes, and a header row that stays put. All local, no upload.
#csv#data#sortingRead more - · Li Lei
How to Normalize CSV Headers: Convert Messy Column Names to Clean snake_case
Turn First Name, first-name, and FirstName into consistent snake_case CSV headers. Trim spaces, strip junk, and make any CSV importable into scripts and databases.
#csv#data-cleaning#developer-toolsRead more - · Li Lei
How to Filter CSV Rows by Column Value Without Excel Formulas
Filter CSV rows by a column condition (contains, equals, greater than) right in your browser. Keep the header, slice exported data fast, and process files locally.
#csv#data-cleaning#filteringRead more - · Li Lei
How to Deduplicate CSV Rows: Drop Identical Rows or Keep One Row per Key
A practical guide to deduplicating CSV rows: remove exact duplicate rows or rows that repeat on a key column like email, with the header preserved.
#csv#data-cleaning#deduplicationRead more - · Li Lei
Profile a CSV for Data Quality Before It Breaks Your Pipeline
A practical guide to using a CSV profiler to catch missing values, duplicates, inconsistent date formats, type mismatches, and outliers before dirty data corrupts a report or import.
#csv#data quality#data profilingRead more - · Li Lei
How to Extract a CSV Column by Name or Index Without a Spreadsheet
Pull one or more columns out of a CSV by header name or position, keep quoted fields intact, and export a smaller file. Runs locally in your browser.
#csv#data#privacyRead more - · Li Lei
Reading a Content Security Policy: How CSP Stops XSS Before It Runs
A practical guide to Content-Security-Policy (CSP): the directives that matter, why unsafe-inline and wildcards weaken script-src, and how nonces ship safely.
#security#csp#xssRead more - · Li Lei
How to Build a Content Security Policy (CSP) Header That Actually Blocks XSS
A practical walkthrough of writing a Content Security Policy header: default-src and script-src directives, allowlisting domains, and why unsafe-inline undoes your work.
#security#csp#web-securityRead more - · Li Lei
Crypto Profit Calculator: Net Profit, ROI, and Break-Even on a Trade
How to calculate profit and loss on a crypto trade with a crypto profit calculator: buy and sell price, amount, both fees, percentage return, and break-even.
#crypto#calculator#tradingRead more - · Li Lei
How to Detect Credit Card Type From the Number: BIN Prefix and Luhn Explained
A practical guide to reading a credit card's network from its first digits — Visa, Mastercard, Amex BIN ranges — plus how the Luhn check digit works.
#credit-card#bin#luhnRead more - · Li Lei
How to Normalize Card Numbers Before You Dedupe or Mask a Data Export
Strip spaces, dashes, and dots from card-shaped strings to get bare digits, so a redaction or test-data pass can dedupe and mask them consistently.
#credit card normalizer#test data#data redactionRead more - · Li Lei
How to Validate Card Numbers With the Luhn Check for Test Data and Redaction QA
Validate card-shaped numbers with the Luhn check and a length test. What Luhn catches, why a valid shape is still only test data, and a worked example.
#luhn#validation#test-dataRead more - · Li Lei
How to Find Card Numbers in Logs: A Card Number Scanner for Leak Detection
Scan logs, exports, and pasted text to find card numbers that slipped through. Learn the 13-19 digit Luhn check and why local detection matters for PCI.
#pci-compliance#data-leak#redactionRead more - · Li Lei
How to Deduplicate Card Numbers When Three Formats Hide the Same Value
A plain text dedupe keeps 4111 1111 1111 1111, 4111-1111-1111-1111, and the bare-digit version as three rows. Here is how to collapse formatting variants into one.
#test-data#deduplication#redactionRead more - · Li Lei
CRC32 Checksum Explained: File Integrity, ZIP, and Why It's Not MD5
A plain guide to the CRC32 checksum: what the 8-hex result means, how ZIP and gzip use it for integrity, why it catches accidental errors but not tampering, and how it differs from MD5.
#crc32#checksum#file-integrityRead more - · Li Lei
CPM Explained: The Cost Per Thousand Impressions Formula and How to Plan a Budget With It
Learn the CPM formula (cost per thousand impressions), how CPM differs from CPC and CPA, and how to size an ad budget by reach with a worked example.
#cpm#advertising#media-buyingRead more - · 李雷
How to Write a Cover Letter That Recruiters Actually Read
A practical guide to cover letter structure, tailoring to a job posting, length, and the mistakes that get you filed in the no pile — with a real before-and-after example.
#cover letter#job search#careerRead more - · 李雷
How to Use a Countdown Timer for Events, Launches, and Exams
A practical guide to the countdown timer: set a target date, share a live link, and watch days, hours, minutes, and seconds tick down to any event or deadline.
#countdown-timer#productivity#date-toolsRead more - · Li Lei
Coulomb's Law Explained: Force Between Two Point Charges
How Coulomb's law works, why force follows an inverse-square rule, and a worked example finding the force between two charges, plus a free calculator.
#physics#electrostatics#coulombs-lawRead more - · Li Lei
Understanding CORS Headers: Why the Browser Blocks Cross-Origin Requests
A practical guide to CORS and the Access-Control-Allow headers: why browsers block cross-origin calls, how preflight works, and the credentials wildcard trap.
#cors#web-security#http-headersRead more - · Li Lei
How to Read a Pearson Correlation Coefficient (r) Without Fooling Yourself
A plain-English guide to the Pearson correlation coefficient r: what its sign and size mean on the -1 to 1 scale, why correlation is not causation, and how scatterplots keep you honest.
#statistics#correlation#data analysisRead more - · Li Lei
GPS Coordinates Explained: Decimal Degrees, DMS, and the Sign That Trips Everyone Up
A plain-English guide to GPS coordinates: how decimal degrees and DMS describe the same point, how to convert between them, and why N/S/E/W becomes a sign.
#gps#coordinates#mapsRead more - · Li Lei
Cooking Units Made Simple: A Measurement Conversion Guide for Cups, Tablespoons, and Grams
Convert cooking measurements between cups, tbsp, tsp, ml and grams the right way. Learn why a cup of flour and a cup of water weigh different amounts.
#cooking#baking#unit conversionRead more - · 李雷
Cooking Measurement Conversion: Cups, Spoons, Grams and mL Without the Guesswork
A practical guide to cooking measurement conversion — cups to grams, tablespoons to mL, US vs imperial vs metric, dry vs liquid, and following foreign recipes accurately.
#cooking#measurement#bakingRead more - · Li Lei
How to Calculate Conversion Rate (and Actually Trust the Number)
The conversion rate formula explained for marketing and ecommerce, plus what counts as a conversion, why benchmarks lie, and the sample size you need first.
#conversion rate#cro#ecommerceRead more - · Li Lei
A Content Refresh Checklist to Update Old Posts and Win Back Rankings
Refreshing old blog content recovers rankings faster than writing new posts. Here is the checklist for updating stats, dates, links, titles, and thin sections.
#content refresh#seo#content operationsRead more - · Li Lei
Find Your Star Sign From a Birth Date: The Real Story Behind the 12 Zodiac Signs
Find your zodiac sign by birthday, see all 12 date ranges, and learn why your star sign no longer matches the actual constellation overhead — plus the cusp question.
#zodiac#astrology#star signsRead more - · Li Lei
What a Confidence Interval Actually Tells You (and What It Doesn't)
A plain-English guide to confidence intervals for a mean or proportion: what 95% really means, the margin of error, and how sample size narrows the range.
#statistics#confidence interval#margin of errorRead more - · Li Lei
How to Estimate Concrete Volume for Slabs, Footings and Columns
Work out concrete volume for a slab, footing or column, convert between cubic yards and cubic meters, count cement bags, add a waste margin and order ready-mix.
#concrete#construction#calculatorRead more - · Li Lei
How to Calculate Engine Compression Ratio from Swept and Clearance Volume
A builder's guide to engine static compression ratio: what the number means, the swept-plus-clearance formula, and how to compute it from bore, stroke, chamber and gasket.
#compression ratio#engine building#automotive mathRead more - · 李雷
How Compound Interest Actually Works: The Formula, Frequency, the Rule of 72, and Why Monthly Investing Wins
A plain-English walkthrough of compound interest: the A=P(1+r/n)^(nt) formula, how compounding frequency changes your return, the Rule of 72, and why steady monthly contributions beat lump sums.
#compound interest#investing#personal financeRead more - · Li Lei
How Sales Commission Actually Gets Calculated: Flat, Tiered, Base Plus Commission, and Draws
A practical guide to sales commission math — flat rate vs tiered brackets, base salary plus commission, draws, and a worked tiered example for reps.
#commission#sales#calculatorRead more - · Li Lei
Combined Gas Law Explained: One Equation for Pressure, Volume, and Temperature
How the combined gas law P1V1/T1 = P2V2/T2 unites Boyle, Charles, and Gay-Lussac, why temperature must be Kelvin, and a worked example you can check.
#chemistry#gas laws#physicsRead more - · Li Lei
Columnar Transposition Cipher: How a Keyword Scrambles a Grid
Learn how the columnar transposition cipher writes a message into a grid under a keyword and reads the columns out in alphabetical order, with a worked example.
#cryptography#ciphers#ctfRead more - · Li Lei
How to Align Columns of Text Into Neat Tables
Align columns of ragged text by a delimiter so every cell lines up in a monospace grid. Pad CSV, TSV, and config rows, right-align numbers, keep CJK width correct.
#column align#align columns#text formattingRead more - · 李雷
Color Temperature Explained: Kelvin, Warm vs Cool Light, and How to Read It
A practical guide to color temperature and Kelvin: why 2700K looks warm and 6500K looks blue, the daylight number photographers trust, and how to preview any Kelvin value as RGB.
#color temperature#kelvin#photographyRead more - · Li Lei
Color Contrast and WCAG: How to Pass AA and AAA
A practical guide to text and background color contrast: WCAG AA needs 4.5:1 for normal text and 3:1 for large text. Worked examples, AAA, and how to fix failing pairs.
#accessibility#wcag#color contrastRead more - · Li Lei
The Collatz Conjecture: Why 3n+1 Always Seems to End at 1
A plain walkthrough of the 3n+1 problem: halve the evens, triple-plus-one the odds, watch every sequence fall to 1, and see why it is still unproven.
#collatz conjecture#3n+1 problem#hailstone numbersRead more - · Li Lei
Flip a Coin Online: Why Every Coin Flip Is Fair and Independent
How a fair digital coin flip works, why each toss is independent, the gambler's fallacy explained, and how to flip many coins at once for quick decisions.
#coin flip#probability#decision makingRead more - · Li Lei
The Coffee to Water Ratio: How a 1:16 Golden Ratio Makes Every Cup Repeatable
Learn the golden coffee ratio (about 1:16), how to scale it by cups, and why weighing your beans beats scooping for pour-over, French press, and cold brew.
#coffee#brewing#ratiosRead more - · Li Lei
Turn Code Into a Polished Image: A Code Screenshot to Image Guide
Turn any snippet into a shareable code screenshot with syntax highlighting, themes, window chrome, and padding. Why an image beats raw code, generated locally.
#code screenshot#code to image#syntax highlightingRead more - · Li Lei
Feeds and Speeds for CNC: How to Find RPM and Feed Rate Without Breaking Tools
A practical guide to CNC feeds and speeds — spindle RPM from surface speed and tool diameter, feed rate from chip load, and why material picks the numbers.
#cnc#feeds-and-speeds#machiningRead more - · Li Lei
Clothing Size Across US, UK, EU and International Charts: Why Centimetres Beat Letters
How to convert clothing size between US, UK, EU and international systems, and why your tape-measured chest and waist in cm beat any S-M-L letter code.
#clothing size#size conversion#online shoppingRead more - · Li Lei
The Circle of Fifths Explained: Keys, Signatures, and Chords
How the circle of fifths organizes keys by perfect fifths, reads sharps and flats, finds relative minors, and builds chord progressions for songwriting.
#music theory#circle of fifths#key signaturesRead more - · Li Lei
Churn Rate, Explained: The Formula, Customer vs Revenue, and Why Small Numbers Hurt
How to calculate customer churn rate for SaaS and subscriptions, the formula, customer vs revenue churn, why small churn compounds, and retention as the flip side.
#churn rate#saas#retentionRead more - · Li Lei
The Chinese Zodiac Explained: Find Your Animal Sign and Read Its Fortune
What the Chinese zodiac is, how the 12-animal cycle maps to your birth year, how to find your sign and its traits, and how the for-fun fortune works.
#chinese-zodiac#culture#fortuneRead more - · Li Lei
How to Find Your Chinese Zodiac Animal by Birth Year
Find your Chinese zodiac animal by birth year, understand the 12-year animal cycle, and learn why a January or February birthday can flip your sign.
#chinese zodiac#astrology#cultureRead more - · Li Lei
China Used Car Value: How to Build a Used Car Price Estimate Before You Sell or Trade In
How dealers in China estimate a used car's value with tiered depreciation rules, plus a worked example showing how age, mileage, and brand tier set the price.
#used-car#china#depreciationRead more - · Li Lei
China Childcare Subsidy After the Three-Child Policy: Why the Three-Child Subsidy Differs by City
China's three-child subsidy isn't one number. Some cities pay a one-time bonus, others a monthly stipend until age 3, plus housing and school perks — here's how to find yours.
#china#parenting#subsidyRead more - · Li Lei
How to Count Chinese Character Strokes (and Why the Number Matters)
A practical guide to counting Chinese character strokes: what counts as one stroke, why the stroke count matters for dictionaries and names, and how simplified and traditional forms differ.
#chinese#language-learning#hanziRead more - · Li Lei
China's Delayed Retirement Reform: Finding Your New Retirement Age and Date
China is raising retirement ages a few months per birth cohort through 2039. Here is how the delayed retirement reform works and how to find your exact new date.
#china retirement age#delayed retirement#pensionRead more - · Li Lei
How to Search Chinese Poetry by a Line, an Author, or a Title
A practical guide to searching classical Chinese poetry — find a Tang shi or Song ci by a half-remembered line, by poet, or by title, and read what it means.
#chinese poetry#tang poetry#song ciRead more - · Li Lei
China's Special Additional Deductions: How Seven Individual Income Tax Items Cut Your Bill
A plain guide to China's seven special additional deductions under individual income tax — children's education, elderly care, rent, mortgage and more — with a worked example.
#china tax#individual income tax#special additional deductionsRead more - · Li Lei
How China Pension Calculation Works: Basic, Personal Account, and Transitional Parts
A plain-English walkthrough of China pension calculation — the pooled basic pension, your personal-account balance, the months divisor, and a worked monthly example.
#china pension#retirement#personal financeRead more - · Li Lei
How to Get a Chinese Name Like 林婉清 That Actually Means Something
A plain guide to how Chinese names work, why family name comes first, what the characters mean, and how to get a real Chinese name instead of a sound-alike.
#chinese name#language learning#chinese cultureRead more - · Li Lei
How China's Maternity Allowance Is Actually Calculated (生育津贴) — Leave Days, Wage Base, and the Numbers HR Won't Volunteer
China's maternity allowance equals the employer's average monthly contribution wage divided by 30, times your maternity-leave days, plus a medical reimbursement. Here is how it works.
#china maternity benefits#maternity allowance#生育津贴Read more - · Li Lei
Understanding China's Betrothal Gift (彩礼 / Caili): Amounts, Regions, and the Law
What caili is, why typical Chinese betrothal-gift amounts swing by an order of magnitude between provinces, and when a 2024 court ruling says it must be returned.
#chinese wedding customs#betrothal gift#cailiRead more - · Li Lei
Reading the Chinese Almanac (Huangli): What a Tongshu Page Actually Tells You
A plain-English guide to the Chinese almanac (huangli / tongshu) — the lunar date, the day's suitable and avoid activities, the zodiac clash, and how families use it to pick dates.
#chinese-culture#huangli#lunar-calendarRead more - · Li Lei
How to Search Chinese Idioms (Chengyu) by Meaning, Character, or Pinyin
A learner's guide to searching Chinese idioms (chengyu) — the four-character form, the story behind each one, and how to look them up by meaning, hanzi, or pinyin.
#chinese#chengyu#language-learningRead more - · Li Lei
China Housing Fund Mortgage Explained: How a Housing Provident Fund Loan Beats the Bank Rate
How China's Housing Provident Fund mortgage works: why the public fund loan rate sits a full point below commercial banks, the per-city loan cap, and the monthly math.
#housing provident fund#china mortgage#public fund loanRead more - · Li Lei
How Chinese Students Pick a College Major After the Gaokao (and the 3+1+2 Catch)
A plain-English walkthrough of how a gaokao score and 3+1+2 subject combo decide which China college major you can apply to, with a worked 580-point example.
#gaokao#china college major#3+1+2 new gaokaoRead more - · Li Lei
China Unemployment Benefits in 2026: How Much Unemployment Insurance You Can Actually Draw
A plain guide to China's unemployment insurance (失业保险金) in 2026 — who qualifies, how months of benefit scale with contribution years, and the city benefit standard.
#china unemployment benefits#unemployment insurance#failbe insuranceRead more - · Li Lei
China Second-Hand House Tax: A Foreigner's Guide to Resale Property Tax (2024 Rules)
What you actually pay to buy a resale home in China: deed tax, VAT, personal income tax, agency fee. The 2-year and 满五唯一 exemptions explained with a worked example.
#china property tax#second-hand house#resale propertyRead more - · Li Lei
China Drink Driving Penalty Explained: The 20/80 BAC Tiers Every DUI in China Hangs On
A clear guide to China's drink driving law for foreign drivers — the two BAC tiers (20 vs 80 mg/100mL), license penalties, fines, and when DUI becomes a criminal charge.
#china drink driving#dui china#bac thresholdRead more - · Li Lei
How China Corporate Income Tax Works for Foreign-Invested Companies
A plain guide to China's Corporate Income Tax for foreign businesses: the 25% standard rate, small low-profit relief, the 15% high-tech rate, and how to model it.
#china-tax#corporate-income-tax#foreign-invested-enterpriseRead more - · Li Lei
The China Child Vaccine Schedule for Expat Parents: Free Class I and Paid Class II Shots, Decoded
A plain-English guide to the China immunization schedule for foreign parents: which childhood vaccines are free, which you pay for, and how to plan from a birth date.
#china child vaccine schedule#china immunization#expat parents chinaRead more - · Li Lei
Child Height Predictor: How the Mid-Parental Method Estimates Adult Height
A plain-English guide to predicting your child's adult height with the mid-parental (target height) formula, the boy/girl adjustment, and why the result is a range.
#child height#adult height prediction#mid-parental heightRead more - · Li Lei
Chengyu Jielong: The Chinese Idiom Chain Game That Grows Your Vocabulary
A guide to chengyu jielong, the Chinese idiom chain game where each new four-character idiom starts with the last character of the previous one. Rules, a worked example, and how to play solo.
#chinese#chengyu#language-learningRead more - · Li Lei
How to Balance Chemical Equations: Coefficients, Mass, and Two Methods
Learn to balance chemical equations the right way: why mass is conserved, how to find coefficients without touching subscripts, and when to swap trial-and-error for the algebraic method.
#chemistry#equations#study-guideRead more - · Li Lei
Character Frequency Counting: From Cipher Cracking to Cleaner Text
How counting each character in text powers cryptanalysis, data cleaning, and linguistics, plus why E is English's most common letter and how case sensitivity changes the math.
#character frequency#frequency analysis#cryptanalysisRead more - · Li Lei
Centripetal Force Explained: How to Use a Centripetal Force Calculator
Centripetal force is the inward pull that keeps anything on a circular path. Learn F=mv²/r with a worked car-cornering example and where the centrifugal myth comes from.
#physics#circular motion#centripetal forceRead more - · Li Lei
How Certificate of Deposit Returns Actually Work: APY, Penalties, and CD Ladders
Understand CD returns the way banks compute them: APY vs APR and compounding, the maturity formula, early-withdrawal penalties, and CD laddering.
#certificate of deposit#cd#apyRead more - · Li Lei
How to Match a Cat Breed to Your Home: Temperament Over Looks
A practical guide to matching a cat breed to your home — weigh energy, grooming, vocal level, lap-cat vs independent, apartment fit, and allergies, not just the coat.
#cat breeds#pet adoption#cat careRead more - · 李雷
The Case Converter Field Guide: camelCase, snake_case, kebab-case, and the Acronyms That Break Them
A practical guide to text case conventions — when to use camelCase, snake_case, kebab-case, PascalCase, and Title Case, plus the acronym and small-word traps that trip up most converters.
#case-converter#naming-conventions#developer-toolsRead more - · Li Lei
How Much Carpet a Room Needs: Roll Width, Waste, and Square Yards
Carpet is sold off a fixed-width roll by the square yard or metre. Here is how to size a room, add a waste margin, and plan seams and pile direction.
#carpet#flooring#homeRead more - · Li Lei
How a Car Loan Actually Works: Monthly Payment, Prepayment, and the Interest You Can Kill
Break down the car loan amortization formula, see exactly how extra payments cut interest and term, and why early prepayments save the most money.
#car loan#prepayment#amortizationRead more - · Li Lei
How a Car Lease Payment Is Actually Built: Money Factor, Residual, and the Rent Charge
A car lease payment is depreciation plus a rent charge plus tax — not price divided by months. Here is the exact math, with money factor and residual.
#car lease#money factor#residual valueRead more - · Li Lei
How a Guitar Capo Transposes Chords: Capo Chords Made Simple
A capo raises every string one semitone per fret, so the shape you finger is not the chord that sounds. Here is how capo chords actually work.
#guitar#capo#music theoryRead more - · Li Lei
Capacitor Energy Explained: Why ½CV² Is About Voltage, Not Capacitance
How energy stored in a capacitor follows E = ½CV², why doubling voltage quadruples joules, and how flash, power smoothing, and safe discharge use it.
#electronics#capacitors#calculatorRead more - · Li Lei
How to Read a 3-Digit Capacitor Code: 104 Means 100nF
Decode the 3-digit number on ceramic capacitors. Learn why 104 equals 100nF, how the significant-figures-plus-power-of-ten rule works, and how to convert pF, nF and µF.
#electronics#capacitors#repairRead more - · Li Lei
Cap Rate Explained: How NOI and Property Value Reveal a Rental's Real Return
Learn the cap rate formula (NOI ÷ property value × 100), a worked example, and what a high vs low capitalization rate signals about risk and growth.
#cap rate#real estate#rental propertyRead more - · Li Lei
How Much Wax and Fragrance a Candle Making Batch Really Needs
Candle recipes are written by volume but wax is sold by weight. Here is the density, fill rate, and fragrance load math to size a candle batch.
#candle making#candle wax#fragrance loadRead more - · Li Lei
How to Set a Calorie Deficit That Actually Works for Fat Loss
Set a daily calorie deficit for fat loss using the 7700 kcal per kg rule, TDEE minus deficit, and why too steep a cut backfires.
#calorie deficit#fat loss#weight lossRead more - · Li Lei
How to Read CAGR: The Honest Way to Annualize Multi-Year Growth
CAGR turns messy multi-year returns into one fair yearly number. Learn the formula, a worked example, why it beats a simple average, and where it misleads.
#cagr#finance#investingRead more - · Li Lei
How the Caesar Cipher Works: Encode, Decode, and Crack a Shift
A plain-English guide to the Caesar cipher: how each letter shifts, why ROT13 is a special case, and why it is a puzzle toy, not encryption.
#caesar cipher#shift cipher#rot13Read more - · Li Lei
Counting Business Days Between Two Dates: A Working Days Calculator Guide
How to count working days between two dates with weekends and holidays excluded, why calendar days mislead project deadlines, SLAs, and shipping estimates.
#business days#working days#project managementRead more - · Li Lei
Buoyancy Force Explained: How Archimedes' Principle Decides What Floats
How buoyancy works through Archimedes' principle, the F = ρ·V·g formula, why ships and balloons float, and a worked example you can check by hand.
#physics#buoyancy#archimedesRead more - · Li Lei
How to Size an Air Conditioner by Room BTU (Without Oversizing)
Size an AC by room BTU using the 20 BTU per square foot rule plus adjustments for ceiling height, sun, occupants, and kitchen heat — with a worked example.
#btu calculator#air conditioner sizing#cooling loadRead more - · Li Lei
Break-Even Calculator: Find the Sales Volume That Covers Your Costs
How to find your break-even point in units and revenue using fixed costs, variable costs, and contribution margin — with a worked example and pricing tips.
#break-even#contribution margin#pricingRead more - · Li Lei
How Braille Works, and How to Turn Any Text Into Braille Dots
A plain-English guide to the six-dot braille cell, Grade 1 letter-by-letter mapping versus Grade 2 contractions, and turning text into Unicode braille.
#braille#accessibility#text-toolsRead more - · Li Lei
Tap Tempo Explained: How a BPM Tap Counter Finds Any Song's Beats Per Minute
How a tap tempo BPM counter works: tap along to any song, the tool averages your tap intervals, and more taps mean a tighter, more accurate reading.
#bpm#tap tempo#musicRead more - · 李雷
How to Calculate a Bond Price: YTM, Premium and Discount Explained
Learn how a bond price is calculated from face value, coupon rate, YTM and maturity. Worked examples for premium, discount and par bonds, plus the present-value formula.
#bond pricing#finance#yield to maturityRead more - · Li Lei
Body Surface Area Explained: The Mosteller and Du Bois BSA Formulas
How body surface area (BSA) is calculated with the Mosteller and Du Bois formulas, and why clinicians dose chemo and pediatric drugs by BSA, not weight.
#body-surface-area#bsa#medical-mathRead more - · Li Lei
How to Calculate Board Feet When You Buy and Build With Lumber
Learn what a board foot is, how lumber is priced by volume, and how to total a cut list for woodworking budgets, including nominal versus actual dimensions.
#woodworking#lumber#board footRead more - · Li Lei
BMR Explained: How to Calculate Basal Metabolic Rate and Use It
A plain-English guide to basal metabolic rate (BMR): the Mifflin-St Jeor and Harris-Benedict formulas, a worked example, and how BMR feeds TDEE and weight goals.
#bmr#basal metabolic rate#tdeeRead more - · 李雷
A Practical Guide to Bitwise Operations: AND, OR, XOR, NOT and Shifts
Learn how bitwise AND, OR, XOR, NOT and bit shifts really work, with worked binary examples, flag and mask tricks, and a free calculator that shows decimal, hex and binary side by side.
#bitwise#binary#developer-toolsRead more - · Li Lei
Bit Shift Explained: Why Left Shifts Double and Right Shifts Halve
A practical guide to bit shift operations — left and right shifts, why a left shift multiplies by two, arithmetic versus logical right shifts, and flags.
#bit shift#bitwise#binaryRead more - · Li Lei
Bionic Reading, Explained: Does Bolding the First Letters Help You Read?
A plain look at bionic reading — how bolding the leading letters of each word guides your eyes, the focus and speed claims, the mixed evidence, and who it helps.
#bionic reading#reading#focusRead more - · Li Lei
The Binomial Theorem Made Practical: Expanding (a + b)ⁿ Term by Term
A working guide to binomial expansion: how the binomial theorem writes (a+b)ⁿ as a sum of C(n,k) terms, where Pascal's triangle comes from, and how to read each term.
#binomial theorem#binomial expansion#algebraRead more - · Li Lei
How to Make Printable Bingo Cards: Classic Numbers vs Custom Words
A practical guide to printable bingo cards — classic 75-ball numbers, custom word and picture bingo, the free center space, and generating unique cards for a group.
#bingo#printables#classroomRead more - · Li Lei
Binary Calculator Guide: Add, Subtract, Multiply and Divide in Base Two
A practical binary calculator guide to adding, subtracting, multiplying and dividing binary numbers, with carries, borrows, a worked example and bitwise context.
#binary#binary arithmetic#computer scienceRead more - · Li Lei
Pulley Speed Made Simple: How Belt Drive Diameters Set Your RPM
How pulley diameters set driven RPM through one belt drive formula, with a worked example and tips for matching speed on a drill press, lathe or fan.
#belt drive#pulley speed#rpmRead more - · Li Lei
The Beaufort Cipher Explained: One Keyword That Both Encrypts and Decrypts
How the Beaufort cipher works, why subtracting plaintext from the key makes it its own inverse, and how it differs from Vigenere, with a worked example.
#cryptography#ciphers#ctfRead more - · 李雷
Why Passwords Need bcrypt, Not MD5: Cost Factor, Salt, and bcrypt vs argon2
A practical guide to bcrypt for password storage: why MD5 fails, how the cost factor and built-in salt work, a real hash walkthrough, and how bcrypt stacks up against argon2.
#bcrypt#password security#hashingRead more - · Li Lei
BCD Explained: How Binary Coded Decimal Keeps Clocks and Displays Honest
A plain guide to binary coded decimal (BCD): how each digit gets its own 4-bit nibble, why hardware prefers it over pure binary, and the size cost.
#bcd#binary coded decimal#number representationRead more - · Li Lei
BBCode to HTML: A Practical Guide to Converting Forum Markup
How BBCode bracket tags map to HTML, with a worked example, rules for nesting and links, and a safe way to migrate old phpBB or vBulletin posts to a modern site.
#bbcode#html#forum-migrationRead more - · Li Lei
Battery Life From mAh and Current Draw: Estimating Real Runtime
How to estimate battery runtime from capacity in mAh and device current draw, why an efficiency factor of 0.8 keeps you honest, and how to size packs for projects.
#battery#electronics#calculatorRead more - · Li Lei
How to Batch Rename Files Safely With a Reviewable Plan
Plan a bulk rename before you touch a single file: build patterns with sequence numbers and tokens, normalize case and slugs, then preview the mv commands to avoid collisions.
#batch rename#rename files#file managementRead more - · Li Lei
The Basic Auth Header Explained: How Authorization Basic Actually Works
How HTTP Basic Authentication builds the Authorization Basic header, why username:password is only Base64-encoded (not encrypted), and why HTTPS is mandatory.
#http#authentication#base64Read more - · Li Lei
Batting Average Explained: Hits, At-Bats, and Why .300 Reads .300
How batting average works — hits over at-bats, the three-decimal scoreboard convention, why walks aren't at-bats, and why on-base percentage tells you more.
#baseball#batting average#sports statsRead more - · Li Lei
Base85 (Ascii85) Explained: Why It Beats Base64 on Size
How Base85 and Ascii85 pack 4 bytes into 5 characters for ~25% overhead instead of Base64's 33%, with a worked example and where PDF and Git use it.
#base85#ascii85#encodingRead more - · Li Lei
Converting Base64 to Hex: Reading the Raw Bytes Underneath
How to convert Base64 to hex by decoding to raw bytes first, why hex is twice as long, and where this byte-level view matters for keys, hashes and certificates.
#base64#hexadecimal#encodingRead more - · Li Lei
Base64 to File: Decode a String Back Into a Downloadable File
A practical guide to turning raw Base64 or a data URL back into a real file in your browser, recovering assets from API responses and logs with auto type detection.
#base64#encoding#developer-toolsRead more - · 李雷
Base64 Encoding Explained: How It Works, Why It Grows Your Data 33%, and When to Use URL-Safe
A practical guide to Base64 encoding: how 3 bytes become 4 characters, why output grows ~33%, the URL-safe variant from RFC 4648, and when Base64 is the wrong tool.
#base64#encoding#web-developmentRead more - · Li Lei
How to Normalize Base64 Blocks Into One Canonical Form
Join line-wrapped PEM blocks, unify URL-safe and standard alphabets, restore padding, and keep case intact. A practical guide to normalizing messy Base64.
#base64#encoding#developer-toolsRead more - · Li Lei
How to Validate Base64 Blocks in a Pasted List Without Decoding Every Line
Validate Base64 blocks from a pasted list: check the A-Z a-z 0-9 + / alphabet, padding, and length, and flag bad characters or misplaced = with a reason.
#base64#validation#encodingRead more - · Li Lei
How to Convert a Base64 Block List into CSV, JSON, and SQL
Turn a plain list of Base64 blocks into CSV, JSON arrays, SQL IN clauses, TypeScript unions, Markdown, or lines for code and data work, locally.
#base64#data-cleanup#developer-toolsRead more - · Li Lei
How to Extract Base64 Blocks From Text, Logs, and PEM Files
A practical guide to pulling Base64 blocks out of messy text, server logs, and PEM files, recognizing the alphabet, joining wrapped lines, all locally.
#base64#encoding#developer-toolsRead more - · Li Lei
How to Deduplicate Base64 Blocks Without Quietly Corrupting Your Data
A practical guide to deduplicating Base64 blocks. Why case-sensitivity is mandatory here, unlike email or UUID dedup, and how to strip duplicate cert, key, and payload blocks safely.
#base64#deduplication#encodingRead more - · Li Lei
Base62 Encoding Explained: Short URLs and Short IDs from Big Integers
How Base62 turns big integer IDs into short URL-safe strings. Why short-link services pick 0-9a-zA-Z, how it beats Base64 in a URL, with a worked example.
#base62#encoding#short-urlRead more - · Li Lei
Base32 vs Base58: Picking the Right Alphabet for Secrets, Addresses, and Short Codes
A practical guide to Base32 and Base58 encoding — why Base32 fits TOTP secrets and DNS, why Base58 suits crypto addresses, and how both compare to Base64.
#base32#base58#encodingRead more - · 李雷
Number Base Converter: Binary, Octal, Decimal, and Hex Explained
A practical guide to converting between binary, octal, decimal, and hex by hand, why programmers reach for hex, and how 255 looks in every number base.
#binary#hexadecimal#number-systemsRead more - · 李雷
How to Use a Barcode Generator: Code 128, EAN-13, UPC-A and Code 39 Explained
A practical guide to picking the right 1D symbology, computing EAN/UPC check digits, and printing barcodes that actually scan — with a real store-shelf example.
#barcode#ean-13#retailRead more - · Li Lei
Baker's Percentage Explained: Hydration, Salt, and Scaling Any Recipe
A plain-English guide to bakers percentage — why flour is always 100%, how to read hydration, and how to scale a bread recipe to any flour weight.
#baking#bread#baker percentageRead more - · Li Lei
Bacon Cipher Explained: Five Bits of A and B Hiding in Plain Text
How the Bacon cipher turns every letter into five A/B symbols, why it doubles as steganography hidden in typography, and how to crack it in CTFs and puzzles.
#bacon cipher#cryptography#steganographyRead more - · Li Lei
Backup Codes and 2FA Recovery Codes: Your Way Back In When the Phone Is Gone
What 2FA backup codes are, why each recovery code works only once, how to store them offline safely, and how to generate a batch locally in your browser.
#security#2fa#backup-codesRead more - · Li Lei
Atom Economy Explained: A Green Chemistry Metric and How to Calculate It
What atom economy means, the formula (product mass over total reactant mass), a worked example, and why it differs from percent yield in green chemistry.
#chemistry#green-chemistry#atom-economyRead more - · Li Lei
The Atbash Cipher: How Reversing the Alphabet Hides (and Reveals) Text
A plain-English guide to the Atbash cipher: how mirroring the alphabet works, why one button encodes and decodes, its ancient Hebrew roots, and CTF uses.
#atbash cipher#classical cryptography#ctfRead more - · 李雷
The ASCII Table Explained: 0–127 Characters, Control Codes, and Printable Glyphs
Understand the ASCII table from character 0 to 127: control codes, printable glyphs, and decimal, hex and binary values, with practical programming uses.
#ascii#character encoding#programmingRead more - · Li Lei
Armstrong Numbers Explained: Why 153 Equals Its Own Digit Powers
A clear guide to Armstrong numbers (narcissistic numbers): the digit-power rule, the famous three-digit set, a hand-checked example, and the classic coding interview question.
#armstrong number#narcissistic number#number theoryRead more - · Li Lei
Learn Arabic Words That Matter: A Core Arabic Vocabulary Guide for Beginners
Start Arabic the honest way. Learn the core 100 Arabic words, read right-to-left script, and understand the three-letter root system that ties it all together.
#arabic#vocabulary#language-learningRead more - · 李雷
APR vs APY: How to Convert Between Them and Stop Comparing the Wrong Numbers
Learn the real difference between APR and APY, how compounding frequency changes your effective rate, and why deposits quote APY while loans quote APR — with a worked example.
#apr-to-apy#interest-rates#personal-financeRead more - · 李雷
How to Generate a Strong API Key: Entropy, Prefixes, and Local Privacy
A practical guide to generating secure API keys: how much entropy you actually need, why prefixes like sk_live_ carry no secrecy, and how to mint keys 100% in your browser.
#api-key#security#developer-toolsRead more - · Li Lei
How to Find Antenna Length From Frequency: Dipole, Quarter-Wave, and Velocity Factor
Turn any frequency in MHz into a resonant antenna length. Half-wave dipoles, quarter-wave verticals, the velocity factor, and a worked ham band example.
#antenna#ham radio#rfRead more - · Li Lei
How an Annuity Calculator Turns Rate and Term Into Real Monthly Numbers
A plain-English guide to present value, future value, ordinary vs annuity-due, and how an annuity calculator turns rate and term into monthly retirement income.
#annuity#retirement#financeRead more - · 李雷
The Anagram Solver That Skips the Dictionary (and Why That's Faster)
Check if two words are anagrams, rearrange any set of letters into every ordering, and read the sorted letter fingerprint. A practical guide with real examples, wildcard tricks, and Scrabble use.
#anagram#wordplay#scrabbleRead more - · Li Lei
Airline Baggage Allowance: A Practical Guide to Carry-on and Checked Luggage Limits
How to check airline baggage allowance, why carry-on and checked luggage limits vary by carrier and cabin, and how to avoid steep overweight fees before you pack.
#travel#baggage allowance#luggage limitsRead more - · Li Lei
How to Count Tokens for LLM Prompts: A Practical Token Counter Guide
Learn what a token is, why token count drives LLM cost and context limits, how counts differ across GPT, Claude, and Gemini, and how to trim prompts.
#ai#tokens#llmRead more - · Li Lei
AI Model Comparison: How to Compare LLMs on the Dimensions That Actually Decide Your Pick
A practical guide to AI model comparison — compare LLMs by context window, price per token, speed, and capability, and learn why the cheapest model rarely wins.
#ai#llm#model comparisonRead more - · Li Lei
How to Plan an AI Evaluation: An LLM Eval Workflow That Catches Real Failures
A practical guide to planning an AI evaluation for an LLM feature: define the task, build a representative test set, pick metrics, and split automated vs human grading.
#ai eval#llm evaluation#ai testingRead more - · Li Lei
The Age Difference Between Two People, Done Right (Years, Months, and Days)
Why subtracting birth years gets the age difference wrong, and how to find the exact gap between two birthdays in years, months, and days for couples and siblings.
#age difference#date math#calculatorRead more - · 李雷
How to Calculate Your Exact Age Down to the Day (Months, Leap Years, and the Edge Cases People Get Wrong)
Most age tools round to the nearest year. This guide shows how to get your exact age in months and days, why Jan 31 trips up month math, and the Feb 29 rule.
#age-calculator#dates#leap-yearRead more - · Li Lei
The Affine Cipher Explained: Why a Must Be Coprime With 26
How the affine cipher E(x)=(ax+b) mod 26 works, why the key a must be coprime with 26, why a=1 is just Caesar, and where it fits in CTFs and teaching.
#cryptography#ciphers#ctfRead more - · Li Lei
Aesthetic Text and Vaporwave Text: How Fullwidth Letters Actually Work
How aesthetic text and vaporwave text work — real fullwidth Unicode glyphs, not a font, so the wide look pastes into any bio or post. Plus caveats.
#aesthetic text#vaporwave text#fullwidthRead more - · Li Lei
How to Encrypt Text with AES and a Passphrase (AES-256-GCM, Done Right)
Encrypt text with a password using AES-256-GCM in your browser. What the key, IV, and salt do, why GCM is the modern default, and when to use it.
#aes#encryption#webcryptoRead more - · Li Lei
How to Add Line Numbers to Text or Code (and Number Lines the Way You Want)
A practical guide to adding line numbers to text or code: padding to align the column, choosing a start value and step, picking a separator, and processing everything locally.
#text#line numbers#developer toolsRead more - · 李雷
How to Add Days to a Date Without Getting the Math Wrong
Learn how to add days to a date the right way — handling month-end rollover, leap years, and business days that skip weekends, with worked examples for contracts and deadlines.
#date calculator#add days to date#business daysRead more - · Li Lei
The A1Z26 Cipher Explained: Turning Letters Into Their Alphabet Position
A1Z26 swaps each letter for its alphabet position — A is 1, Z is 26. A plain-language guide to the simplest substitution cipher, with a worked HELLO example.
#ciphers#puzzles#ctfRead more - · Li Lei
555 Timer Calculator: Frequency, Duty Cycle and Pulse Width from R and C
How to size R1, R2 and C for an NE555. Astable frequency f=1.44/((R1+2R2)C), duty cycle, and monostable pulse width, with a worked LED blinker example.
#555 timer#ne555#electronicsRead more - · Lei Li
URL Encoding vs Percent Encoding vs Form Encoding: One String, Three Different Outputs
Percent encoding, URL encoding, and form encoding sound interchangeable until a space character breaks your query string. I ran one real string through all three pipelines — here is exactly where they diverge and why.
#url#encoding#web-developmentRead more - · Lei Li
Unicode, UTF-8, and Emoji Character Counts: Why Text Length Tools Disagree
JavaScript says 11, Python says 7, your database says 25, and your eyes say 1. A practical walk through graphemes, code points, UTF-16 units, and UTF-8 bytes — with real measured numbers.
#unicode#utf-8#emojiRead more - · Lei Li
React Hooks Pitfalls That Survive Code Review (and the Cheat Sheet Habit That Catches Them)
Stale closures in useEffect, useId values that crash querySelector, useMemo that makes renders slower — four hook traps that pass review looking correct, with the actual broken code and the fix for each.
#react#javascript#frontendRead more -
How to Use a Words Per Minute Calculator to Nail Your Speech Length
Learn how to calculate speaking rate and estimate speech duration accurately — with real examples for keynotes, podcasts, and voiceovers.
#speaking#wpm#speechRead more -
How Developers Use Test Credit Card Numbers Without Touching a Real Gateway
A practical guide to generating Luhn-valid test card numbers for payment form testing, database seeding, and fuzzing — without using real PANs or sandbox accounts.
#payments#testing#developer-toolsRead more - · Lei Li
BaZi Calculator: What Your Eight Characters Actually Tell You
BaZi (Four Pillars) gives you eight stem-branch characters from your birth year, month, day, and hour. This guide explains each layer — pillars, Day Master, Five Elements bars, Ten Gods — and shows a worked example so you know what to look at once your chart appears.
#chinese-astrology#bazi#four-pillarsRead more -
Rune Translator: Elder Futhark for Tattoos, Games, and Decoding Real Inscriptions
A practical guide to translating English into Elder Futhark runes and back — how two-letter sounds work, what makes a rune tattoo accurate, and how to decode glyphs you find in games or on artifacts.
#runes#elder-futhark#tattooRead more -
How to URL Encode and Decode Query Parameters Safely: A Developer's Field Guide
Learn the difference between encodeURIComponent and encodeURI, when + vs %20 breaks your API, and how to handle edge cases like nested objects and special characters.
#url-encoding#query-string#web-developmentRead more -
The Next.js 15 Cheat Sheet I Reach For: Caching Flips and the Server/Client Line
The two Next.js 15 changes that broke my muscle memory — fetch is no longer cached by default, and the client router cache went stale-by-zero. Real snippets, the exact pitfalls, and where to look them up fast.
#nextjs#app-router#server-componentsRead more - · Lei Li
Unicode, UTF-8, and ASCII Explained for Everyday Developer Tools
A practical guide to Unicode, UTF-8, and ASCII for developers who debug byte counts, pasted text, invisible characters, URLs, JSON, and database limits.
#unicode#utf-8#asciiRead more - · Lei Li
How to Safely Encode Text for APIs, Webhooks, and Query Strings
A practical checklist for encoding text in API calls, webhook signatures, redirect URLs, and query strings without corrupting plus signs, spaces, Unicode, or signed payloads.
#encoding#api#webhooksRead more -
How Many Days Until a Date? A Calculator That Counts the Way Planners Think
Counting days to a deadline by hand is where errors creep in. Here is how the Days Until Date Calculator handles leap years, business days, and the off-by-one trap — with a worked example to Christmas 2026.
#date#productivity#calculatorRead more - · Lei Li
Six Encodings Developers Use Every Day: URL, Base64, Hex, Unicode Escapes, HTML Entities, and Percent Encoding
A practical hub for telling URL encoding, Base64, Hex, Unicode escapes, HTML entities, and percent encoding apart, with real outputs and conversion rules.
#encoding#base64#urlsRead more - · Lei Li
Clean pinyin columns for rosters and CSVs
A practical guide to using Toolora's Chinese Pinyin Converter for name rosters, CSV cleanup, username drafts, and mixed Chinese-English records.
#pinyin#chinese#csvRead more - · Lei Li
Test titles before publishing
A practical headline-analyzer workflow for scoring blog titles, comparing variants, and turning headline feedback into publishable SEO copy.
#seo#copywriting#contentRead more - · Lei Li
Build a SERP and social title lab
Use Toolora's headline analyzer as a small title lab for SEO posts: compare SERP fit, social fit, clickbait risk, and snippet support before publishing.
#seo#copywriting#contentRead more - · Lei Li
Refresh SEO titles without clickbait
A practical workflow for using Toolora's headline analyzer to audit old SEO titles, compare variants, and pair the final headline with a better snippet.
#seo#copywriting#contentRead more - · Lei Li
Turn a content brief into publishable titles
A practical headline-analyzer workflow for turning a content brief into honest SEO title options, with a real Toolora input/output example.
#seo#copywriting#contentRead more - · Lei Li
Welcome to Toolora
What Toolora is, who it's for, and the 15 tools we'd reach for first across five everyday personas.
#intro#toolsRead more