Cron expressions are famously terse — five space-separated fields that decide exactly when your backups run, your emails send, and your reports generate. They are also famously easy to get wrong. This visual builder lets you pick values with dropdowns or start from common presets, shows the equivalent expression, describes it in plain English, and previews the next execution times, so you can be confident before pasting anything into a crontab.
Understanding Cron Syntax
A standard cron expression has five fields, in this order: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–7, where both 0 and 7 mean Sunday). The special characters do the heavy lifting. An asterisk * matches every value; a comma lists alternatives (0 9,17 * * * runs at 9 AM and 5 PM); a hyphen defines a range (0 9 * * 1-5 runs at 9 AM on weekdays); and a slash sets a step (*/15 * * * * runs every 15 minutes).
The classic trap is combining day-of-month with day-of-week: when both are restricted (neither is *), cron runs when either field matches, not both. So 0 0 13 * 5 fires on the 13th and on every Friday — not only on Friday the 13th. Knowing this one rule prevents a lot of surprise executions.
How to Use
- Select values: Choose minute, hour, day, month, weekday
- Use presets: Select common schedules
- View expression: See the generated cron expression
- Copy: Copy to clipboard
Features
- Visual cron expression builder
- Common presets (every minute, hourly, daily)
- Human-readable description
- Copy to clipboard
- Preview of upcoming execution times
Use Cases
Sysadmins schedule nightly backups, log rotation, and certificate renewals. Developers queue report generation, cache warming, and cleanup jobs. Data teams orchestrate ETL pipelines. The expression you build here works in classic crontabs and, with minor dialect differences, in GitHub Actions, Kubernetes CronJobs, AWS EventBridge, and most modern schedulers.