How do I validate a cron expression?

Paste your cron expression into SimpleCronTab. It will instantly tell you if the expression is valid, what it means in plain English, and when it will next run.

What are common cron expression errors?

Common errors include: wrong number of fields (should be 5 for standard cron), values out of range (e.g., month 13), invalid step values (e.g., */0), and typos in field separators.

Cron Expression Validator

0 */4 * * 1-5

Every weekday from 12:00 AM to 12:59 AM, 4:00 AM to 4:59 AM, 8:00 AM to 8:59 AM, 12:00 PM to 12:59 PM, 4:00 PM to 4:59 PM, and 8:00 PM to 8:59 PM

Next 10 Executions

Times shown in UTC

Mon, May 18, 202612:00
Mon, May 18, 202616:00
Mon, May 18, 202620:00
Tue, May 19, 202600:00
Tue, May 19, 202604:00
Tue, May 19, 202608:00
Tue, May 19, 202612:00
Tue, May 19, 202616:00
Tue, May 19, 202620:00
Wed, May 20, 202600:00

Field Breakdown

0

Minute

*/4

Hour

Every 4 hours

*

Day of Month

Every day

*

Month

Every month

1-5

Day of Week

Mon, Tue, Wed, Thu, Fri

About This Schedule

A cron expression validator checks whether a cron string is syntactically correct and shows you what schedule it produces. Paste an expression like 0 */4 * * 1-5 and the validator tells you it means "at minute 0 past every 4th hour, Monday through Friday."

Validation catches common mistakes: wrong number of fields, values out of range, invalid step syntax, and conflicting day-of-month and day-of-week combinations. Catching these errors before deployment prevents silent failures where your cron job never runs.

SimpleCronTab validates in real time as you type, showing errors inline and previewing the next 10 execution times. It supports standard 5-field cron, Quartz 6-field, and AWS EventBridge formats.