Build and explain cron expressions interactively. See next run times and human-readable descriptions.
The Cron Expression Builder helps you construct, validate and understand cron schedule strings without memorising the syntax. Type an expression directly or use the visual field-by-field builder, and the tool instantly translates it into plain English and shows the next five scheduled run times. A library of common presets lets you start from a working example in one click.
The builder parses cron expressions using the standard five-field format (minute, hour, day-of-month, month, day-of-week) and supports the full syntax including ranges (1-5), step values (*/15), lists (1,3,5), and shorthand names (MON, JAN). To compute the next scheduled run times, it iterates forward from the current moment until it finds five matching timestamps - all calculations run in the browser using your device's local clock and timezone.
Yes - while the five-field standard is universal, many cloud platforms extend it. AWS EventBridge and Google Cloud Scheduler support a six-field format that adds a seconds field or a year field. Jenkins and Quartz use a seven-field variant. GitHub Actions cron syntax follows the standard five-field POSIX format, while some platforms interpret ? in the day fields differently. Always consult the documentation of your specific platform and test with a tool that previews actual run times before deploying.
Use the expression */15 9-17 * * 1-5 - this fires every 15 minutes (minute field: */15), between 9 AM and 5 PM inclusive (hour field: 9-17), on Monday through Friday (day-of-week field: 1-5). Note that cron runs in the server's local timezone, so if your server is set to UTC you will need to adjust the hour range to match your target timezone offset. Use a timezone-aware scheduler like AWS EventBridge if accurate local time scheduling is critical.
The most frequent mistake is confusing the day-of-week field numbering: on most systems Sunday is 0 or 7, Monday is 1, and Saturday is 6. Another common error is expecting */60 in the minute field to mean "every hour" - it is actually invalid on many systems, and 0 * * * * is the correct expression for hourly jobs. Mixing day-of-month and day-of-week restrictions in the same expression also produces unexpected results because most cron implementations treat them as an OR condition rather than AND.
crontab.guru is the de-facto standard reference for cron expression explanation and is excellent for quick translation of a single expression to English. This builder adds a visual field-by-field construction interface, a library of common presets, and a next-five-run-times preview - making it faster to build expressions from scratch without needing to know the syntax upfront. Both tools are complementary: use this builder to construct and validate, and crontab.guru as a secondary sanity check for complex patterns.