Cron Expression: Run Every Hour (0 * * * *)
The standard crontab expression to execute a task once every hour at the top of the hour (minute 0) is `0 * * * *`. This interactive schedule tester validates the expression, translates it into natural language, and simulates the next upcoming execution timestamps entirely in your browser with zero server latency.
#How to Use This Tool
#Mathematical Formula & Standards
#Edge Cases & Technical Considerations
Asterisk in Minute Field Trap (* * * * *)
A common beginner mistake is writing `* * * * *` expecting an hourly job. However, `*` in the minute field causes the command to execute EVERY MINUTE of every hour. To run once per hour, the minute field MUST be a specific number like `0`.
Top-of-the-Hour Load Spikes (Thundering Herd)
If thousands of servers schedule database backups or cache warming at `0 * * * *`, shared infrastructure can experience extreme CPU and I/O spikes. Consider offsetting the minute (e.g., `17 * * * *` or `43 * * * *`) to distribute load evenly.
#Frequently Asked Questions
Q:What is the cron expression for running every hour?
The standard cron expression is `0 * * * *`. It triggers at the start of every hour (e.g., 00:00, 01:00, 02:00).
Q:How do I run a cron job at half past every hour?
Use `30 * * * *`. This fires at minute 30 of every hour (00:30, 01:30, 02:30, etc.).
Q:How do I run every 2 hours?
Use `0 */2 * * *`. This fires at minute 0 of every second hour (00:00, 02:00, 04:00, etc.).
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