Sudoku generator and solver — 4 difficulties (easy / medium / hard / expert), unique-solution guaranteed, play in the browser or print as PDF.
- Runs locally
- Category Generator
- Best for Starting from a blank page without committing to the first result.
What this tool does
A working sudoku workshop in one tab. Press "New puzzle" and it back-tracks a fresh 9×9 from scratch, carves holes one cell at a time, and re-runs a solver after each hole to confirm the puzzle still has exactly one solution — so what you print or play is guaranteed unique, not "looks unique because we stopped checking." Four difficulty bands map to the number of givens left behind: Easy keeps 39–43, Medium 32–37, Hard 26–31, Expert reaches the lower bound at 22–25 (anything lower and unique solutions get rare even with backtracking).
Play it in the browser: tap a cell, tap a number, mistakes light up against the live solution, Hint fills the cell you're stuck on, Undo walks the move stack back. The clock runs from the first move and pauses when you finish. Drop in your own residual puzzle, hit Solve, and you get the completed grid plus a step-by-step trace of the back-tracking solver (good for verifying that a magazine puzzle actually has one solution, not two). Print sends a clean A4 page with the puzzle on top and the solution upside-down at the bottom — coffee shop and classroom friendly.
One extra: the Daily Sudoku is deterministic by date (UTC), so every player worldwide gets the same puzzle on the same calendar day. Progress saves to localStorage, so closing the tab does not lose your board. 100% client-side: no API, no signup, no tracking.
Tool details
- Input
- Text + Numbers
- The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
- Output
- Live result
- The result area focuses on usable output, with copy, download, or preview actions when supported.
- Privacy
- Browser-side processing
- The main tool logic does not call an external API, so inputs normally stay in the current tab.
- Save / share
- Local preference storage
- Preferences, history, or drafts are saved in this browser without an account.
- Performance budget
- Initial JS <= 25 KB
- No WASM budget is declared, keeping the tool quick to open on mobile.
- Best fit
- Generator · Student
- Category and role tags drive related tools, internal links, and quick fit checks.
How to use
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1. Input
Paste or drop your content into the tool panel.
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2. Process
Click the button. All processing is local in your browser.
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3. Copy / Download
Copy the result or download to disk in one click.
How Sudoku Generator fits into your work
Use it to get a strong first draft, starter asset, or structured output that you can edit before publishing.
Generation jobs
- Starting from a blank page without committing to the first result.
- Creating repeatable drafts, names, templates, or placeholder assets.
- Exploring options before choosing the one that fits the job.
Generation checks
- Review generated output before it reaches a customer, page, or document.
- Change defaults when you need a specific brand voice, format, or audience.
- Keep only the parts that match the real task.
Good next steps
These links move the current task into a more complete workflow.
- 1 Chinese Poetry Search Chinese classical poetry — 300+ hand-annotated Tang/Song/Yuan canon (唐诗宋词元曲) plus 80,000+ searchable Tang/Song/Shijing/Chuci poems on demand. Open
- 2 Scientific Calculator Scientific calculator — sin / cos / log / sqrt / power, with full keyboard input + history, deg/rad mode. Open
- 3 Math Formula Reference Math formula reference — algebra, geometry, trigonometry, calculus, statistics, all in one place. Open
Real-world use cases
Print a week of puzzles for a classroom warm-up
A grade-5 teacher needs five Medium grids for Monday-Friday morning starters. Generate one, hit Print, change the difficulty, repeat — five A4 sheets in two minutes, each with the solution upside-down at the bottom so the answer key never gets separated from the puzzle. No login, no watermark, no 30-puzzle-per-month paywall.
Verify a newspaper puzzle that looks ambiguous
You are halfway through a magazine Sudoku and stuck because two digits seem to both fit a cell. Switch to Solve mode, type the printed givens, press Solve. If it returns "multiple solutions" the magazine printed a broken puzzle (a clue was dropped at the press); if it returns the grid, you missed a logic step, not them.
Race the Daily Sudoku with a friend in another timezone
You are in Berlin, your sister is in Mexico City. You both open the Daily Sudoku on Expert, same calendar day, and the UTC date seed gives you the identical grid. Screenshot the start, time yourselves, compare. No account, no friend-add flow, no server keeping score — just the same 22-given puzzle and a stopwatch each.
Train one specific solving technique on demand
You want to drill X-wings before a puzzle tournament. Set the level to Expert and keep pressing New puzzle: the 22-25 given band reliably forces advanced patterns rather than naked singles. Use Hint when you want the tool to point at the next logically-forced cell, and Undo to re-run the same board state after a wrong guess.
Common pitfalls
Leaving difficulty on Easy and wondering why no advanced technique ever appears — Easy keeps 39-43 givens, so naked singles solve everything; switch to Expert for X-wings.
In Solve mode, typing a wrong given (say 8 instead of 3) then blaming "no solution" on the tool — re-check your transcription cell by cell, the solver is reporting your input is inconsistent.
Expecting the print sheet to keep your pencil marks — print intentionally drops candidate marks and prints only the original givens plus the upside-down solution, so mark up the paper copy instead.
Privacy
Everything runs in your browser. The grid you generate or paste, the timer, the move stack, and your chosen difficulty are stored only in this tab's localStorage — nothing is sent to a server and nothing is written to the URL, so pasting a newspaper puzzle to solve it never leaves your machine. Clearing site data or pressing New puzzle wipes the saved board.
FAQ
Tool combos
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