What does * mean in cron?

The asterisk (*) in cron means "every" or "any value". For example, * in the minute field means "every minute", and * in the day field means "every day".

How do I run a cron job every 5 minutes?

To run a cron job every 5 minutes, use the expression "*/5 * * * *". The */5 in the minute field means "every 5 minutes".

Cron Expression Generator

Build cron expressions visually. Get human-readable explanations and see the next scheduled run times.

Quick presets

Minute

Hour

Day (Month)

Month

Day (Week)

Cron Expression

0 * * * *

Human readable

Every hour, on the hour

Next 5 runs

Sat, Dec 27, 09:00 PM

Sat, Dec 27, 10:00 PM

Sat, Dec 27, 11:00 PM

Sun, Dec 28, 12:00 AM

Sun, Dec 28, 01:00 AM

Cron Syntax Reference

Field	Allowed Values	Special Characters
Minute	0-59	* , - /
Hour	0-23	* , - /
Day of Month	1-31	* , - / L W
Month	1-12 or JAN-DEC	* , - /
Day of Week	0-6 or SUN-SAT	* , - / L #

Special Characters

* — Any value
, — Value list separator
- — Range of values
/ — Step values

Common Examples

*/15 * * * * — Every 15 minutes
0 */2 * * * — Every 2 hours
0 9-17 * * 1-5 — Hourly 9-5 weekdays
0 0 1,15 * * — 1st and 15th of month

What is a Cron Expression?

A cron expression is a string consisting of five fields that represent a schedule. Originally from Unix systems, cron expressions are now used everywhere — from Linux crontab to cloud schedulers like AWS EventBridge and GitHub Actions.

The Five Fields

A standard cron expression has five fields, separated by spaces:

┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-6, Sunday=0)
│ │ │ │ │
* * * * *

Tips for Writing Cron Expressions

Start simple — Begin with presets and modify from there
Test your expression — Always verify the next run times
Consider timezones — Cron typically runs in server timezone
Avoid minute 0 — Many jobs run at :00, causing load spikes
Monitor your jobs — Use heartbeat monitoring to ensure jobs complete

Cron vs Crontab

Cron is the daemon (background service) that executes scheduled commands. Crontab (cron table) is the file where you define your scheduled jobs. Each line in a crontab file contains a cron expression followed by the command to run.

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