Cron recipe
Cron job every 30 seconds: the exact expression
The expression
*/30 * * * * *Paste it into crontab -e, your platform cron config, or tool.crontap.com/cronjob-debugger to preview the next runs.
What it does
Six-field Quartz-style syntax: seconds first, then minute, hour, day, month, weekday. `*/30` in the seconds field means every 30 seconds. Most Linux `cron` daemons ignore a sixth field.
When to use it
Quartz, Spring, or AWS EventBridge
Platforms that explicitly support a seconds field.
When you thought you needed 30-second cron
Often a sign you want a long-running worker or queue consumer instead of cron.
Common variations
* * * * *Closest portable five-field equivalent: every minute on Crontap or Linux cron.
Run this with Crontap
External HTTP cron hits your URL on this schedule, stores every response, and emails you when a run fails. No daemon on the box, no drift when the server reboots. Pro schedules down to a 1-minute cadence; $3.25/mo annual flat for unlimited jobs.
Related recipes
More patterns in the cron syntax cheat sheet and what is a cron job in Linux.
FAQ
- What is the cron expression for every 30 seconds?
- Use */30 * * * * * (six fields with seconds first). Verify the next run times in the free cron debugger before you deploy.
- Can Crontap run this schedule?
- Standard Linux crontab and Crontap use five fields (minute resolution). Crontap's fastest schedule on Pro is every 1 minute. For true sub-minute work, use an in-process scheduler or a worker loop; do not expect `crontab` to fire twice per minute.