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Cron expression explainer
Cron syntax is dense: five fields of asterisks, slashes, and ranges that are easy to misread. Paste any standard crontab expression below to get a plain-English description, a field-by-field breakdown with range validation, and the next five times it will actually run. Everything is computed in your browser; nothing is sent to a server.
Five fields, space-separated: minute · hour · day-of-month · month · day-of-week.
Everything runs in your browser. No expression is ever sent anywhere.
Try an example
In plain English
At 09:00 on Monday through Friday.
Field breakdown
| Field | Value | Meaning |
|---|---|---|
| Minute | 0 | 0 |
| Hour | 9 | 9 |
| Day of month | * | Every day of the month |
| Month | * | Every month |
| Day of week | 1-5 | Monday through Friday |
Next 5 runs
(your local time)Calculating…
How to read a cron expression
Read the five fields left to right: minute, hour, day of month, month, and day of week. A job fires when the current time satisfies every field at once. The value 0 9 * * 1-5 means minute 0, hour 9, any day of the month, any month, on days 1 through 5. In other words, 09:00 every weekday.
Frequently asked questions
- What are the five cron fields?
- A standard crontab line has five space-separated fields, in order: minute (0 to 59), hour (0 to 23), day of month (1 to 31), month (1 to 12), and day of week (0 to 6, where 0 is Sunday). A job runs when the current time matches all of them.
- What do the special characters mean?
- An asterisk (*) matches every value in the field. A slash sets a step, so */15 means "every 15 units". A hyphen makes a range, like 1-5 for Monday through Friday. A comma lists specific values, like 0,30 for the top and half of the hour. You can combine them: 0-30/10 runs at 0, 10, 20, and 30.
- How do day-of-month and day-of-week interact?
- When both the day-of-month and day-of-week fields are restricted (neither is *), cron treats them as an OR: the job runs when either one matches. This explainer follows that rule, so "0 0 1 * 1" fires on the 1st of the month and on every Monday.
- Are the next run times accurate for my timezone?
- The next-run list is computed in your browser using your local clock, so it reflects your machine’s timezone. A real cron daemon evaluates the schedule in the server’s timezone, so confirm the server clock if the two need to line up.
- Is my cron expression sent anywhere?
- No. Parsing, the plain-English translation, and the next-run calculation all happen entirely in your browser with no network requests. Nothing you type leaves the page.