Cron Expression Builder

What a cron expression actually says

Cron is the scheduling language behind Linux servers, CI pipelines, database backups, and cloud jobs. A single line packs five fields — minute, hour, day-of-month, month, and day-of-week — into terse symbols like 0 3 * * 1. That reads as "at 3:00 AM every Monday," but the syntax is easy to misread, and a wrong asterisk can mean a job fires every minute instead of once a week. This builder turns the cryptic string into a plain-English sentence so you can confirm it does what you meant before you paste it into a crontab or a scheduler.

When you'd reach for it

Reach for it when you're writing a crontab -e entry, filling in the schedule box for a GitHub Actions workflow, a Kubernetes CronJob, a Jenkins trigger, or an AWS EventBridge rule. It's also handy for reading someone else's config during a code review — you can check "does */15 9-17 * * 1-5 really mean every 15 minutes during business hours on weekdays?" without keeping the field order in your head.

A worked example

Take 30 2 1 * *. Field by field: minute 30, hour 2, day-of-month 1, any month, any weekday — so "at 2:30 AM on the 1st of every month." Swap the 1 for * * 1 and the meaning jumps to every Monday. The step syntax */5 means "every 5 units," a range like 1-5 means Monday through Friday, and a list like 1,15 means the 1st and 15th. Ranges and steps combine, which is where mistakes hide.

How to use it

1. Type a five-field expression into the box, or click a preset like "every day at midnight" to start from a known-good line.
2. Read the plain-English translation that updates as you type, and check each field matches your intent.
3. Adjust a single field — for example change * to 1-5 to limit it to weekdays — and watch the sentence change.
4. Copy the finished expression into your crontab, CI file, or scheduler.

FAQ

Is Sunday 0 or 7?

In the day-of-week field, 0 and 7 both mean Sunday in most cron implementations; 1 is Monday through 6 for Saturday. Names like SUN and MON also work in many schedulers.

What time zone does the schedule use?

Cron itself has no time zone — it runs in whatever zone the host or service is set to, often UTC on cloud platforms. Always confirm the server's zone, because 3 AM there may not be 3 AM for you.

Does it support seconds or the special "@reboot" syntax?

This builder focuses on the standard five-field format. Some tools add a sixth seconds field or shortcuts like @daily; those are extensions, so check your specific scheduler's docs.

Is it free, and does anything leave my machine?

It's free and ad-supported, and it runs entirely in your browser — nothing you type is uploaded.