View future cron matches in a calendar
Showing next 1000 cron schedules
CronTool runs every keystroke through the same parser used by production schedulers. It validates:
*/n), range (1-5), list (1,15), and alias (MON-FRI) syntax.?, L, W, #.0 0 31 2 * validates syntactically but never fires; the tester surfaces this.Different schedulers parse cron differently. CronTool covers the popular dialects out of the box:
?, no L.L, ?, #.L, W, #, ?.Want to gate your deploys on a valid cron? Pair @datasert/cronjs-parser (the parser CronTool uses) with cronstrue in a Node script and run it as a pre-commit / pre-deploy step. The browser tester is the visual version; the CLI test is the same logic in your pipeline.
Field-by-field syntax, value ranges, day-of-month / day-of-week conflicts, support for the modifier you used (`L`, `W`, `?`, `#`) in the chosen mode, and that the expression actually has at least one future match. If any of those fail, the offending field is highlighted and the parser error is shown verbatim.
Yes — toggle the extended-cron switch in the top bar. AWS EventBridge uses a 6-field syntax (with year) and supports `?` and `L` modifiers. CronTool's tester runs the same parser used in production schedulers, so the calendar matches what EventBridge will actually do.
Yes. Quartz supports 6 or 7 fields (seconds and optional year) plus `?`, `L`, `W` and `#`. Use the extended-cron mode and CronTool will accept Quartz-compatible syntax. Note: Quartz forbids both day-of-month and day-of-week being non-wildcard simultaneously — the tester flags it.
Yes — Vercel cron jobs use standard 5-field cron syntax (timezone is always UTC). Test the expression in CronTool's default mode, then drop it into your `vercel.json` `crons` array. Note Vercel's free plan caps cron frequency at once per hour; the tester doesn't enforce platform-specific limits.
Validation is purely syntactic — the parser accepts or rejects the string. Testing goes further: it computes the next runs, projects them onto a calendar, and lets you eyeball whether the schedule actually matches your intent. CronTool does both in real time as you type.
Not built-in, but the same parser CronTool uses (`@datasert/cronjs-parser` and `@datasert/cronjs-matcher`) is available on npm if you want to script tests in CI. Pair it with `cronstrue` for the natural-language description.
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