Cron Job Every 30 Minutes

The expression

*/30 * * * *  /path/to/command

The */30 step fires at minute 0 and minute 30 of every hour — 48 runs per day. It is identical to writing 0,30 * * * *. Both forms are widely used; the list form is sometimes preferred because it reads as an explicit "at :00 and :30".

Shifting the half hour

If you would rather run at quarter-past and quarter-to, list the minutes directly:

15,45 * * * *  /path/to/command

This still runs every 30 minutes, but at :15 and :45 instead of :00 and :30. Offsetting like this is a simple way to avoid colliding with other top-of-hour jobs on a busy server.

Useful variations

• */30 9-18 * * 1-5 — every 30 minutes, 9am–6pm, weekdays.
• 0,30 * * * 0,6 — every 30 minutes on weekends only.
• 15,45 8-20 * * * — offset half-hour runs during the day.
• 0,30 0-6 * * * — every 30 minutes overnight for batch processing.

Choosing the right cadence

Thirty minutes suits jobs that are moderately expensive — report generation, mailbox polling, syncing a remote cache — where running every five minutes would waste resources and once an hour would feel stale. If a single run risks taking longer than 30 minutes, guard it with a lock so two copies never overlap. As always, paste your final line into the generator to confirm the meaning and preview the next executions before committing it to your crontab.