This explainer reads classic crontab syntax: stars, numbers, comma-separated lists, inclusive ranges, steps, and three-letter month or weekday names. It intentionally rejects seconds, years, and Quartz-only symbols such as ?, L, W, and #, because those belong to different scheduler dialects.
Private browser utility / Developer
Free Cron Expression Explainer
Runs entirely in your browser - no upload, no sign-up.
Five fields: minute, hour, day of month, month, day of week.
Paste a cron expression to explain itYou will get a plain-English summary, a field breakdown and the next five UTC run times.
What does a cron expression explainer do?
A cron expression explainer translates a standard five-field Unix cron schedule into plain English. Paste an expression to see its overall meaning, what each minute, hour, day, month and weekday field selects, and the next five matching UTC run times. It validates the syntax locally as you type.
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How to use
- 01Paste the expression
Enter a standard five-field cron expression in minute, hour, day-of-month, month and day-of-week order.
- 02Read the schedule
Check the plain-English summary and inspect each field card to see its source value, allowed range and meaning.
- 03Verify the next runs
Review the next five UTC timestamps and any warning about day-field OR behavior or an impossible date.
- 04Copy the explanation
Copy the complete summary and field breakdown for a ticket, runbook or code review.
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Who it's for
- Developers checking a schedule copied from a repository, deployment file or CI configuration.
- System administrators reviewing backups, maintenance jobs and cleanup tasks before changing a crontab.
- Incident responders confirming when a job should fire without decoding five compact fields under pressure.
- Technical writers adding a readable schedule explanation to runbooks and internal documentation.
FAQ
Is this cron expression explainer free?
Yes. The cron expression explainer is free, needs no account and has no usage limit. Validation, translation and run-time calculation happen in your browser, so you can check as many standard five-field expressions as you need.
Is my cron expression uploaded?
No. Your cron expression is parsed and explained locally by JavaScript in your browser. It is not uploaded for processing, which is useful when a schedule reveals internal job names, maintenance windows or infrastructure details.
Which cron format does the explainer support?
It supports standard five-field Unix cron in minute, hour, day-of-month, month and day-of-week order. Fields may contain stars, lists, upward ranges, steps, and three-letter month or weekday names. It does not accept a seconds or year field.
What does */15 9-17 * * MON-FRI mean?
It runs every 15 minutes during hours 09 through 17 on Monday through Friday. Because cron steps restart within their field, the matching minutes are 00, 15, 30 and 45 during every selected hour.
Why does the explainer warn about two day fields?
Traditional cron uses OR behavior when both day-of-month and day-of-week are restricted. A job can run when either field matches. That differs from the intuitive AND reading, so the tool calls it out before you paste the expression into a scheduler.
Are the next run times in my local timezone?
No. This page shows next runs in UTC so the preview stays consistent and unambiguous. A real cron daemon usually evaluates schedules in the server timezone unless its configuration or platform lets you choose another zone.