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Cron Expression Explainer
Explain a cron expression in plain English, or build one from a schedule with no syntax to memorize.
Updated July 7, 2026
How to use the cron expression explainer
- 1In Explain mode, type or paste a cron expression. The English translation updates live.
- 2Or switch to Build mode and pick a frequency, time, and days to generate the expression.
- 3Copy the generated expression, and check the syntax table for what each symbol means.
- 4Confirm the English matches your intent before deploying, and mind the server's time zone.
Common uses
- Sanity-checking a crontab entry before it goes to production
- Decoding a cron schedule you found in an unfamiliar codebase or CI config
- Writing schedules for GitHub Actions, Vercel Cron, or Kubernetes CronJobs
- Learning cron syntax by editing presets and watching the English change
Frequently asked questions
What are the five fields?
In order: minute (0–59), hour (0–23), day of month (1–31), month (1–12), day of week (0–6, Sunday = 0). '30 18 * * 5' reads: minute 30, hour 18, any day, any month, Friday, 6:30 PM Fridays.
What happens when day-of-month AND day-of-week are both set?
The classic gotcha: standard cron ORs them. '0 9 13 * 5' runs at 9 AM on the 13th AND on every Friday, not only Friday the 13th. If you need the intersection, put the second condition in the script itself.
How do steps like */15 work?
'Every Nth value': */15 in the minute field fires at :00, :15, :30, :45. Steps combine with ranges too. 9-17/2 in the hour field means every 2 hours from 9 AM through 5 PM.
Why did my job run at the wrong hour?
Time zones. Cron uses the host machine's zone, which on servers is usually UTC, so '0 9' means 9 AM UTC, not your local morning. Check the server's zone, and remember DST shifts can double-fire or skip jobs scheduled in local-time zones.
About this tool
The cron expression tool works both ways. Explain mode translates crontab schedules into plain English as you type: 0 9 * * 1-5 becomes 'At 9:00 AM, on Monday through Friday.' It handles the full standard 5-field syntax, wildcards, exact values, ranges, steps (*/15), lists, and named months and weekdays, plus one-click presets and a syntax reference. Build mode is the reverse: pick a frequency (every N minutes, daily at a time, weekly on chosen days, monthly on a date) and it generates the correct expression with a live English preview and one-click copy, no memorizing field order. Cron's terseness is its trap: the fields are easy to transpose, day-of-month and day-of-week interact in a way almost nobody remembers, and a mistake means a job silently running at 3 AM daily instead of monthly. Reading it back in English before deploying is the cheap insurance.
Like most tools on UtilityBase, the cron expression explainer runs entirely in your browser. Nothing you enter is uploaded or stored on a server. It's free to use with no account required. Browse more developer tools here.
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