Cron Expression for Every 30 Seconds

Cron does not support seconds. Use two entries or a scheduler.

Why Cron Cannot Do This

Standard cron has five fields: minute, hour, day-of-month, month, and day-of-week. The smallest granularity is one minute. There is no seconds field.

Workaround: Two Cron Entries

You can approximate every-30-seconds by combining two entries in your crontab:

* * * * * /your/command
* * * * * sleep 30 && /your/command

The first runs at the top of each minute. The second sleeps 30 seconds, then runs the same command — giving you two executions per minute, 30 seconds apart.

Better Alternatives

• systemd timers — support sub-second precision on Linux
• Node.js / Python schedulers — use setInterval or APScheduler
• Kubernetes CronJob — pair with a sidecar loop for sub-minute intervals

Try the Cron Expression Builder to create and test cron schedules.

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