About the Cron Explainer
The cron tool explains a cron expression by validating its five fields and previewing the next run times in your local timezone. It supports the standard syntax including asterisks, comma lists, ranges with a dash, step values with a slash, and names like mon or jan.
Use it to double-check a crontab entry or scheduled job before deploying it, or to understand what an unfamiliar schedule actually does. It runs locally in the browser, so you get instant feedback without sending your schedules to any service.
How to use it
- Enter a five-field cron expression, such as 0 9 * * mon.
- Check that each field validates without errors.
- Read the plain-language explanation of the schedule.
- Review the previewed next run times in your local timezone.
Examples
- 0 9 * * mon runs at 09:00 every Monday.
- */15 * * * * runs every 15 minutes.
- 0 0 1 jan * runs at midnight on January 1st each year.
Frequently asked questions
What cron format does it use?
Standard five-field cron: minute, hour, day of month, month and day of week. It supports *, comma lists, dash ranges, slash steps and month/weekday names.
What timezone are the next run times in?
The previewed run times are shown in your local browser timezone, so they reflect what you would see on your own machine.
Can I use names like mon and jan?
Yes. Three-letter weekday names (mon-sun) and month names (jan-dec) are supported in addition to numbers.
Does it support seconds or special strings like @daily?
No. It parses the classic five-field format, so six-field (seconds) expressions and macros like @daily are not handled.
Is my cron expression sent anywhere?
No. Parsing, validation and the next-run preview all happen locally in your browser; nothing is uploaded.
What is the difference between */15 and 15 in a field?
*/15 means every 15 units (a step), so 0, 15, 30, 45, while a plain 15 means only at the single value 15.