HyperMonitors
Free tool

Cron expression tester

Paste a cron expression to see what it actually means and when it will run next. Runs entirely in your browser — nothing is sent to a server.

This means

Every 5 minutes every day

Next 5 runs

UTC
Fri 21 Aug, 11:15Next
Fri 21 Aug, 11:20
Fri 21 Aug, 11:25
Fri 21 Aug, 11:30
Fri 21 Aug, 11:35

The five fields

FieldAllowed valuesNotes
Minute0–59Minute of the hour the job starts.
Hour0–2324-hour clock, in the server's local timezone.
Day of month1–31Combined with day-of-week using OR when both are set.
Month1–12, JAN–DECNames are case-insensitive: JAN, jan, Jan.
Day of week0–6, SUN–SAT0 and 7 both mean Sunday. Names SUN–SAT also work.

Syntax you can use

*

Every value — every minute, every hour, every day.

1,15,30

A list of specific values.

9-17

An inclusive range.

*/15

Every Nth value, starting at the lowest.

0-30/10

Every Nth value within a range.

Common questions

Why does my job run more often than expected?

Almost always the day-of-month and day-of-week fields. Cron combines them with OR, not AND: if both are set to something other than *, the job runs whenever either one matches. To get “Friday the 13th” you need a check inside the job itself, because cron cannot express it.

Which timezone does cron use?

The local timezone of the machine running it, which is often UTC on a server even when you are not. That means a schedule can shift by an hour twice a year when daylight saving changes, and a job scheduled during a spring-forward gap may not run at all that day. This tool shows the next runs in your browser timezone, which is displayed above the list.

Can I run a job every 30 seconds?

Not with standard cron — the smallest unit is one minute. Some implementations add a seconds field, but it is not portable. The usual workaround is a job that runs every minute and sleeps, or a proper scheduler.

How do I know if a cron job did not run?

Cron itself will not tell you: a job that never starts produces no output and no error. The usual approach is a heartbeat — the job calls a URL when it finishes, and you get alerted if that call does not arrive on schedule.

Get alerted when a cron job silently stops

A cron job that fails to run is invisible — there is no error, because nothing ran. Add a heartbeat monitor and HyperMonitors alerts you when the expected check-in does not arrive. The free plan includes 5 monitors.

Monitor a cron job free

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