What is a cron expression?

A cron expression is a string of five space-separated fields that represent a schedule. The fields are: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6). For example, '0 9 * * 1-5' means 9:00 AM every weekday.

How do I validate a cron expression?

Enter your cron expression in the input field on CronTab.space. The validator instantly checks the syntax and shows any errors. Valid expressions display a human-readable description and the next 5 scheduled execution times.

What does the asterisk (*) mean in cron?

The asterisk (*) in a cron expression means 'every' or 'any value'. For example, * in the minute field means every minute, and * in the day field means every day of the month.

How do I schedule a cron job to run every 5 minutes?

To run a cron job every 5 minutes, use the expression '*/5 * * * *'. The */5 in the minute field means every 5th minute, and the asterisks in other fields mean any hour, day, month, and weekday.

Can I generate a cron expression using natural language?

Yes! CronTab.space features an AI-powered generator. Simply type your schedule in plain English like 'every Monday at 9am' or 'twice daily' and the AI will generate the correct cron expression for you.

AI Cron Generator

Describe your schedule in plain English. We translate it into a cron expression you can copy or refine in the visual builder.

Build by field

click to refine each part

AI cron generator

describe it in English

Cron, in plain English

Type what you want. We’ll write the expression.

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Next runs

in a few secondsTue, Jul 14, 05:30 PM UTC

in 15 minutesTue, Jul 14, 05:45 PM UTC

in 15 hoursWed, Jul 15, 09:00 AM UTC

in 15 hoursWed, Jul 15, 09:15 AM UTC

in 16 hoursWed, Jul 15, 09:30 AM UTC

Use it in

# /etc/crontab
*/15 9-17 * * 1-5  user  /usr/local/bin/your-script.sh

Snippets are templates — replace placeholders with your script and paths.

Going to production? Cron won’t tell you when it fails.

Standard cron silently skips runs when the machine is off, the script crashes, or the network drops. Get an alert the moment a scheduled run misses its window.

Monitor with cronradar

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Cron, in 90 seconds

A cron expression is five fields separated by spaces. Each field controls one piece of the schedule: minute, hour, day of month, month, day of week.

min

0–59

hour

0–23

dom

1–31

mon

1–12

dow

0–6

Special characters: * any, , list, - range, / step.

FAQ

An asterisk matches every valid value for that field. In the minute field it means every minute; in the hour field, every hour, and so on. "* * * * *" runs every minute of every hour, every day.

Both. Standard cron accepts 0 and 7 as Sunday. Day-of-week runs Sunday=0, Monday=1, ..., Saturday=6, with 7 also recognized for Sunday in most implementations.

No. Standard cron only fires at the exact scheduled times — there is no catch-up. If you need missed-run recovery, look at anacron, systemd timers with Persistent=true, or a job scheduler like Quartz.

Quartz uses 6- or 7-field expressions with seconds and optional year, plus extras like "L" (last) and "#" (nth weekday). Standard Unix cron is 5 fields: minute, hour, day-of-month, month, day-of-week.

Cron runs in the timezone of the system or the configured TZ. During DST transitions, a missing hour is skipped and a repeated hour fires twice. Use UTC scheduling for predictable behavior across regions.