What cron expression runs every 3 hours starting at midnight?

The cron expression `0 */3 * * *` runs every 3 hours starting at midnight. Paste this into your crontab file, Vercel cron config, GitHub Actions schedule, or any cron-compatible scheduler.

How do I test the cron expression 0 */3 * * *?

Use a cron tester like crontab.guru or run `crontab -l` to list current jobs. For dry-run testing, many schedulers (Vercel, GitHub Actions, AWS EventBridge) have a "test schedule" or "preview next runs" button.

How do I add "0 */3 * * *" to my crontab?

Run `crontab -e` to edit your crontab, add a new line with `0 */3 * * * /path/to/your-command`, and save. The command will run on the schedule you specified. Check `/var/log/syslog` or `journalctl -u cron` for execution logs.

Does this cron expression work on Vercel / GitHub Actions / AWS?

Yes, `0 */3 * * *` is a standard 5-field POSIX cron expression (or 6-field for Quartz/Spring). It works on Vercel Cron Jobs, GitHub Actions (`schedule: [{ cron: '0 */3 * * *' }]`), AWS EventBridge, Google Cloud Scheduler, Kubernetes CronJobs, and most Linux cron daemons.

Cron Expression: Every 3 hours starting at midnight

Cron Expression

0 */3 * * *

Every 3 hours starting at midnight

Click the expression to select it, then copy.

Quick Answer

The cron expression for "every 3 hours starting at midnight" is `0 */3 * * *`. Copy and paste this into your crontab, Vercel cron config, GitHub Actions workflow, or any standard cron-compatible scheduler.

Field-by-Field Breakdown

Field	Value	Meaning
Minute	0	At minute 0
Hour	*/3	Every 3 hour
Day of Month	*	Every day of month
Month	*	Every month
Day of Week	*	Every day of week

Common Use Cases

→Regular backups
→Stats rollup
→Cache invalidation

How to Use This Expression

Vercel Cron Jobs

// vercel.json
{
  "crons": [{
    "path": "/api/your-endpoint",
    "schedule": "0 */3 * * *"
  }]
}

GitHub Actions

# .github/workflows/scheduled.yml
on:
  schedule:
    - cron: '0 */3 * * *'

Linux crontab

0 */3 * * * /path/to/your-command.sh

Frequently Asked Questions

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