Question 1

What is a cron expression?

Accepted Answer

A cron expression is a string of 5 or 6 fields separated by spaces that defines a schedule for recurring tasks. The fields represent minute, hour, day of month, month, day of week (and optionally seconds). It is widely used in Linux crontab, Jenkins, Kubernetes CronJobs and task schedulers.

Question 2

What does * * * * * mean in cron?

Accepted Answer

Five asterisks * * * * * means every minute. Each asterisk is a wildcard meaning every value for that field. For example, 0 * * * * means at minute 0 of every hour (hourly), and 0 0 * * * means at midnight every day (daily).

Question 3

How do I run a cron job every day at 9am?

Accepted Answer

Use 0 9 * * *. This means: at minute 0, hour 9, every day of month, every month, every day of week. You can also select 9:00 AM Daily from the presets in this tool.

Question 4

What is the difference between 5-field and 6-field cron?

Accepted Answer

Standard Unix cron uses 5 fields (minute hour day month weekday). Some systems like Quartz Scheduler and Spring add a leading seconds field, making it 6 fields. This tool supports both formats — toggle the seconds field as needed.

⚡

⚙️

🕐