What is Cron?
Cron is a time-based scheduler on Unix-like systems. A cron expression has five fields — minute, hour, day of month, month, and day of week — that together define when a job runs, such as */5 * * * * for every five minutes.
Cron is used to automate recurring tasks like backups, report generation, and cleanup jobs. Many platforms and libraries reuse the same expression syntax.
Key points
- Five fields: minute, hour, day-of-month, month, day-of-week.
- * means "any"; */n means "every n"; a-b is a range; a,b is a list.
- Schedules align to the clock, not to when the last run finished.
- Jobs run in the server timezone — often UTC.
Example
*/5 * * * * → every 5 minutes 0 9 * * 1-5 → weekdays at 9 AM
Common uses
- Scheduling backups and cleanup jobs
- Sending recurring emails or reports
- Polling APIs and refreshing caches
- Running any recurring background task
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Open the Cron Expression