Does this support 6-field cron (with seconds)?

No — only the classic 5-field POSIX cron used by /etc/crontab and Linux/macOS user crontabs. Six-field variants (Quartz, Spring, BusyBox in some builds) add a leading seconds field and a trailing year field, and the syntax for day-of-week differs (0–6 vs 1–7). Mixing them up silently shifts schedules. If you need Quartz, use a Quartz-specific tool — the rules are different enough that one UI can't honestly cover both.

What's the difference between `* * * * 1` (Monday) and `* * 1 * *` (1st of the month)?

Field position. The fifth field is day-of-week (0 = Sunday … 6 = Saturday, with 7 also meaning Sunday on most implementations) and the third field is day-of-month (1–31). `* * * * 1` fires every minute, all day, every Monday — about 1,440 runs per Monday. `* * 1 * *` fires every minute, all day, only on the 1st of each calendar month. When both day-of-month and day-of-week are set (neither is `*`), Vixie cron — the most common implementation — treats it as "OR", which surprises people.

Will cron still fire if my laptop is asleep at the scheduled time?

On Linux servers, classic cron will not catch up missed jobs (anacron does, if installed and configured). On macOS, launchd is what actually runs your "cron" lines, and it has the `StartCalendarInterval` + missed-run replay behavior built in for jobs added via launchctl, but `crontab -e` entries still go through legacy cron which does not replay. The safe pattern for laptops: use launchd directly, or use systemd timers with `Persistent=true` on Linux, both of which replay a missed run on wake.

What's the smallest interval cron actually supports?

One minute. The minute field is the finest grain — `* * * * *` fires every minute. To run more often than once a minute you need a different scheduler (a sleeping loop in your process, systemd timer with `AccuracySec=1s`, or a job queue with a fast tick). Note: even at `* * * * *`, cron's wakeup is not millisecond-precise; jobs typically start within the first 1–2 seconds of the minute.

Crontab Helper — Build, Explain & Preview Cron Expressions

Visual crontab builder + human-readable explanation + next run preview.

Runs locally
Category Format Converter
Best for Turning pasted content or local files into a handoff-friendly format.

Expression

Explanation

Every 5 minutes

Next 5 runs (local time)

2026-05-29 21:35
2026-05-29 21:40
2026-05-29 21:45
2026-05-29 21:50
2026-05-29 21:55

Presets

Minute

Every

Hour

Day of month

Month

Day of week

What this tool does

Build cron expressions without remembering the field order. Five side-by-side panels (minute, hour, day-of-month, month, day-of-week) each offer the four real-world patterns: "every", "every N", "specific values", and "range". The expression updates as you click, with a plain-English explanation under it ("Every 4 hours, at minute 0") and the next five firing times computed for your local clock. Paste an existing line like `*/15 9-17 * * 1-5` and the UI parses it straight back into the panels so you can edit visually. Eight named presets cover the patterns people actually write — hourly, daily at 3 AM, every weekday business hours, monthly on the first, etc. All math runs in the tab; nothing is sent anywhere.

Tool details

Input: Numbers + Structured content; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy + Preview; 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: No account required; Open the page and use it; whether results survive refresh depends on the tool.
Performance budget: Initial JS <= 20 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Crontab Helper — Visual Builder & Explainer fits into your work

Use it when the main problem is getting content from one practical format into another.

Conversion jobs

Turning pasted content or local files into a handoff-friendly format.
Previewing a conversion before you use it in a larger workflow.
Cleaning small format mismatches without opening a full editor.

Conversion checks

Try a small sample first when the source format is messy.
Check character encoding, separators, and line endings after conversion.
Keep the source until the converted output has been reviewed.

Good next steps

These links move the current task into a more complete workflow.

FAQ

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Crontab Helper — Build, Explain & Preview Cron Expressions

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Crontab Helper — Visual Builder & Explainer fits into your work

Conversion jobs

Conversion checks

Good next steps

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