Crontab checker with Cron Studio
The Audit tab opens with a sample crontab full of classic mistakes. Paste your own (crontab -l) and every line is explained and checked. Free covers the first three jobs.
- Run crontab -l (or open /etc/crontab) and paste the output.
- Read each job's plain-English schedule and the findings under it.
- Fix bugs first, then risks; notes are informational.
- Re-paste to confirm the findings are gone.
What to know
Most "my cron job does not run" problems are not syntax errors. They are the unescaped %, which cron turns into a newline so date +%F breaks; a command that depends on a PATH cron does not have (cron starts with /usr/bin:/bin); output that goes to local mail nobody reads; and schedules that mean something other than you think.
The checker flags schedules that never run (0 0 31 2 *), lines with both a day of the month and a weekday (cron runs on either), jobs every minute that can overlap themselves, schedules between 01:00 and 03:59 local time, which run twice or not at all on daylight-saving change days, and several jobs all set to minute 0 of the same hour, which makes a server do ten things in the same second. Each finding says why it matters and what to change.
Everything runs in your browser; your crontab is not uploaded. Paste a copy with secrets removed anyway if the lines contain tokens or passwords, because crontabs often hold more than schedules: database URLs, API tokens and hostnames are common in command lines, and they are better kept in a protected environment file.
Updated · Cosmovex
Questions
How do I check if my crontab is valid?
Paste it into the Audit tab. Each line is parsed with the same rules cron uses, errors are shown with the field that is wrong, and common mistakes are flagged.
Why does a % in my crontab break the command?
In a crontab, an unescaped % is a newline; everything after the first one is passed to the command as standard input. Escape it as \% or put the command in a script.
Why does my cron job work in the shell but not in cron?
Cron runs with a minimal environment and PATH. Use absolute paths, set PATH at the top of the crontab, and redirect output to a log so you can see the error.
Is my crontab uploaded anywhere?
No. The audit runs in your browser and nothing you paste is sent to our servers.
The free plan covers everything on this page. Cron Studio Pro ($19, paid once) is described on the Cron Studio page.
