developer-tools

Cron Expression Parser

Parse five-field Unix cron expressions locally in your browser, expand field meanings, and preview upcoming run times.

Tool workspace

The interactive tool requires JavaScript.

Instructions

1. Enter a five-field Unix cron expression in the order minute hour day-of-month month day-of-week.
2. Choose browser local time or UTC, and optionally set the preview start and row count.
3. Click "Parse Cron" to see expanded fields, dialect notes, and upcoming run times.
4. Use the result as a static check, then compare seconds, timezone, and special syntax with the target scheduler documentation.

Paste a cron expression such as */15 9-17 * * MON-FRI to inspect minute, hour, day-of-month, month, and weekday fields. Preview upcoming runs in your browser local timezone or UTC without creating a job or contacting a server.

The Cron Expression Parser supports five-field Unix cron plus common @hourly, @daily, @weekly, @monthly, and @yearly macros. It explains the dialect, timezone mode, day-of-month versus weekday OR semantics, and previews a limited number of future runs within a 366-day window. Quartz seconds, year fields, and provider-specific syntax are outside scope.

Supported cron dialect

The tool focuses on five-field Unix cron: minute, hour, day of month, month, and weekday. It supports numbers, ranges, lists, steps, English month and weekday aliases, and common macros such as @hourly, @daily, @weekly, @monthly, and @yearly.

Timezone and preview limits

Preview can run in browser local time or UTC and shows up to 12 future times strictly after the chosen starting minute. The search stops after 366 days; 0 9 1 1 * started at 2026-01-01 09:00 UTC therefore returns 2027-01-01 09:00 UTC, not the starting instant.

Not a replacement for the scheduler

Platforms may use Quartz, Kubernetes, GitHub Actions, or cloud-provider extensions. Before production changes, compare the expression with the target scheduler documentation and actual execution logs.