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A cron expression is a string of five space-separated fields that defines a recurring schedule. The fields represent minute, hour, day of month, month, and day of week. Special characters like * (every), / (step), - (range), and , (list) create flexible scheduling patterns used by Unix cron, CI/CD pipelines, cloud schedulers, and task automation tools.
The */5 syntax means "every 5th interval" starting from 0. In the minute field, */5 fires at minutes 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 55. You can use any step value: */2 means every 2nd, */10 means every 10th, and so on.
Day of month (field 3) specifies calendar dates like the 1st or 15th. Day of week (field 5) specifies named days like Monday (1) or Friday (5). If both are set to specific values, most cron implementations run the job when either condition is met (OR logic), not both (AND logic).
This tool supports the standard 5-field cron format used by Unix crontab, most cloud schedulers (AWS, GCP, Azure), and popular libraries like node-cron. Some systems like Quartz use 6 or 7 fields with seconds and year, but those are non-standard extensions not covered here.
No. All cron parsing, expression building, and next-run-time calculations happen entirely in your browser using JavaScript. Nothing leaves your machine.