Crontab validator
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Crontab
Per-line
# daily report
L2
0 9 * * 1-5 → at minute 0, at hour 9, on weekday 1-5 · /usr/bin/reportL3
*/15 * * * * → every 15 minutes · /usr/bin/heartbeatL4
0 0 1 * * → at minute 0, at hour 0, on day-of-month 1 · /usr/bin/monthly-archiveWhat this tool does
Paste a whole crontab and see comments, valid lines, and invalid lines side by side.
Tip
Add comments above scheduled lines to remember why a job exists. Cron does not.