Cron Decoder - decode any cron expression online

Paste the cron into the editor. CronTool shows editable labeled fields, a plain-English sentence, five next runs in the selected timezone, and a navigable month calendar.

It places each token in an editable labeled field with a help popover for range and syntax. The combined sentence, five next runs, and calendar show the resulting schedule; CronTool does not display a semantic AST.

Decoding takes a cron string and explains it. Writing (or building) goes the other way - you describe the schedule in your head and compose the cron string. Use the cron builder for the latter, or the cron tester to validate as you write.

L selects a last occurrence, W the nearest weekday, # an nth weekday, and ? leaves a day field unspecified. Exact support depends on the dialect.

It means every 5 minutes: minute values 0, 5, 10, and so on through 55. It does not mean only the fifth minute of each hour. Expression: */5 * * * *

A literal 5 means minute 5 of every hour, such as 09:05 and 10:05. The step */5 means every five minutes. Expression: 5 * * * *

For Vixie cron, 0 9 1 * 1 means every Monday OR every first day of the month. Quartz and AWS instead require ? in one day field. Expression: 0 9 1 * 1

It means 09:00:00 on the second Monday of every month in a Quartz-style extended expression. The ? leaves day-of-month unspecified. Expression: 0 0 9 ? * MON#2

No. A step selects values inside one field and resets at the boundary. In day-of-month, */7 selects 1, 8, 15, 22, and 29, then restarts next month. Expression: 0 0 */7 * *

Field validity does not guarantee a possible date. 0 0 30 2 * uses legal values but asks for February 30, so CronTool reports that it never fires. Expression: 0 0 30 2 *

The sentence describes clock fields, while the selected timezone controls the next-run timestamps and calendar. Confirm that timezone against the scheduler's actual configuration.

It can parse many six- and seven-field forms in Extended mode, but it does not identify or validate a target dialect. Use the dialect matrix and Copy as output, then verify the result with AWS or Quartz.

Yes. CronTool never executes the scheduled command. In production, however, PostHog events may include valid, copied, or shared cron strings, so do not assume the expression remains only in the tab.

Share /?cron=<expression> and add mode=extended when needed. Add tz=<IANA zone> if the decoded timestamps must use the same timezone; Copy link omits timezone.

No. It explains and validates the schedule only; it cannot see your server's PATH, environment, permissions, logs, or command result, and it never executes commands.