Cron Explainer
Turn cron expressions into readable schedules.
| Field | Value |
|---|---|
| Minute | 0 |
| Hour | 9 |
| Day of month | * |
| Month | * |
| Day of week | 1-5 |
Enter a valid five-field cron expression to see a plain-language explanation.
Cron Explainer turns five-field cron expressions into plain language in your browser. See a field-by-field breakdown, catch parser errors early, and copy human-readable schedules—cronstrue loads dynamically so the page stays lightweight.
How it works
Enter a standard minute-hour-day-month-weekday expression. The tool validates field count, then calls cronstrue to produce a verbose English description. Invalid tokens or unsupported syntax return explicit error messages.
Benefits
- Plain-language explanations for standard cron
- Field breakdown table for quick scanning
- Parser errors surfaced clearly
- cronstrue loaded on demand
- Runs locally with no upload step
Use cases
- Verify Kubernetes CronJob schedules before deploying
- Document backup windows for runbooks
- Decode legacy crontab entries during migrations
- Teach cron syntax with immediate feedback
Best practices
- Confirm five-field format matches your scheduler
- Document timezone assumptions separately—cron is timezone-local
- Prefer explicit ranges over magic numbers in shared configs
- Test edge cases like last-day-of-month patterns in staging
Common mistakes
- Using six fields when the platform expects five
- Swapping day-of-month and day-of-week constraints
- Assuming */5 in the hour field means every five minutes
- Forgetting that some engines use 0 or 7 for Sunday
Privacy
Cron parsing happens entirely in your browser via a dynamically imported library. ToolHub does not receive your expressions. Optional device history stores inputs only if you explicitly enable and save them locally.
Frequently asked questions
- Which cron format does this tool support?
- Standard five-field Unix cron: minute, hour, day of month, month, and day of week. Expressions with other field counts show a clear validation error.
- Does Cron Explainer upload my schedules?
- No. Parsing uses cronstrue loaded dynamically in your browser. Your expressions never leave your device.
- Why do I see a field count error?
- Most schedulers expect exactly five whitespace-separated fields. Six-field variants with seconds are not supported in this tool.
- Can I copy the plain-language explanation?
- Yes. Use Copy to grab the generated description, or Download to save it as a text file.
- Does day-of-week numbering match my server?
- cronstrue follows common Unix conventions (0 or 7 = Sunday). Always confirm against your scheduler docs for cloud-specific quirks.
- Why is cronstrue loaded lazily?
- The parser library is dynamically imported so the tool page stays fast until you actually explain an expression.
- What if the expression is invalid?
- Parser errors surface as readable messages—fix the offending field rather than getting a silent empty result.
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