Cron Builder
Build, validate and understand cron expressions with ease. Create cron schedules in seconds – no memorization required.
1. Build your cron expression
Understanding cron expression
| Field | Required | Allowed values | Allowed special characters | Examples |
|---|---|---|---|---|
| Minute | Yes | 0-59 | * , - / | 0, */5, 0-30 |
| Hour | Yes | 0-23 | * , - / | 9, 9-17, */2 |
| Day of month | Yes | 1-31 | * , - / ? | *, 1, 1-15 |
| Month | Yes | 1-12, JAN-DEC | * , - / | *, 1, JAN |
| Day of week | Yes | 0-6, SUN-SAT | * , - / ? | *, 1-5, MON-FRI |
2. Your cron expression
3. Next execution times
(UTC+0)Tips
- * — any value
- , — value list separator
- - — range of values
- / — step values
- ? — no specific value (day of month or weekday)
Your data stays private
Everything is processed locally in your browser. We never upload or store your data.
About five-field cron in the browser
Cron Builder composes a UNIX-style five-field expression: minute, hour, day of month, month, day of week. Builder dropdowns and presets (weekdays at 9 AM is a common start) update a live expression, a plain-English summary, and next run times. Editor lets you type a string. Seconds (six-field) are not supported. ? on day fields is treated like *.
Worked example: 0 9 * * 1-5 is 09:00 Monday–Friday. Lists, ranges, and steps follow common cron rules. Next-run times use this device’s clock interpretation of the expression — confirm against the system that will actually run the job (UTC vs local is a frequent production bug).
Cron Explainer is the reverse: paste an existing string. This is not systemd OnCalendar and not GitHub Actions cron with different weekday numbering. Nothing is uploaded.
How to build a cron expression
Pick the fields
Choose minute, hour, day, month, and weekday — or start from a preset.
Read the schedule
The expression, plain-English summary, and next run times update as you change fields.
Copy or edit
Copy the 5-field cron, or open the editor to type an expression directly.
Stays private
Parsing and next-run times run in this tab. Nothing is uploaded.
Common use cases
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Cron Builder FAQ
Use the Builder dropdowns or a quick preset (Weekdays at 9 AM is the default). The 5-field expression, plain-English summary, and next run times update as you change fields. Switch to Editor to type a cron string. Nothing is uploaded.
Minute, hour, day of month, month, and day of week. Use * for every, lists, ranges, steps, and names like MON-FRI. ? is treated like * for day fields. Seconds (6-field) expressions are not supported.