Cron Expression Parser
Parse cron expressions, see human-readable descriptions, and preview the next run times in any timezone
Interactive tool
Cron expression
What is a Cron Expression Parser?
A cron parser translates compact cron expressions like "0 9 * * 1-5" into plain English and computes the next run times. It is the fastest way to verify that a schedule means what you think it means before deploying it.
How to Use This Cron Expression Parser
- 1Type or paste a cron expression (5-field format)
- 2Pick the timezone the schedule should run in
- 3Adjust how many upcoming run times you want to preview
- 4Read the human-readable description and verify the next runs
- 5Choose 12-hour or 24-hour formatting to match your team
Key features
Human-Readable Output
Translates cron expressions into clear English using cronstrue
Validation
Catches syntax errors with a clear message so you know which field is wrong
Next Run Preview
Lists the next 1 to 20 run times with date, weekday, and relative time
Timezone Aware
Pick the timezone your scheduler runs in so previews match production reality, including DST
12 or 24 Hour Format
Toggle output format to match your team conventions
Field Breakdown
Shows minute, hour, day-of-month, month, and day-of-week fields side by side
Common Presets
One-click presets for hourly, daily, weekly, and monthly schedules
100% Private
Parsing runs in your browser. Nothing is uploaded
Why Verify Cron Expressions?
Cron syntax is terse and easy to misread. A schedule that fires every minute instead of every hour can flood logs and burn budget. A parser that explains the schedule in English and previews the next runs eliminates this class of bug before it ships.
Common use cases
- Verifying scheduled job expressions before deployment
- Documenting cron schedules in plain English for runbooks
- Translating crontab entries from legacy systems
- Planning cron schedules for new services
- Debugging a job that runs at the wrong time
- Comparing schedules across services
- Onboarding teammates to cron syntax
- Sanity-checking scheduled report generation
Cron Syntax Quick Reference
Five fields: minute (0-59), hour (0-23), day-of-month (1-31), month (1-12 or names), day-of-week (0-6 or names). Wildcards: * matches anything, , lists values, - ranges, / steps. Example: "*/15 9-17 * * 1-5" means every 15 minutes between 9am and 5pm on weekdays.
Timezone and DST
Cron schedules typically run in the system timezone. Pick the matching IANA zone in the parser to see exactly when the job will fire. The preview accounts for DST transitions automatically.
Tips & best practices
Always pick the right timezone
A schedule in UTC fires at different local times than the same expression in America/New_York. Match the parser to your scheduler
Watch for "every minute" mistakes
A bare * in the minute field means every minute. If you meant once an hour, use 0 instead
Use ranges and steps
0-30/5 means every 5 minutes from 0 to 30. Steps work in any field and keep expressions short
Day-of-month vs day-of-week
When both are set, the schedule fires on either condition. Most platforms treat them as OR
Test with the preview
Always glance at the next 5 runs before deploying. Mistakes look obvious in the preview
Privacy & security
This cron parser runs entirely in your web browser using the cron-parser and cronstrue libraries. Inputs are never uploaded to any server, stored anywhere, or transmitted. All parsing happens locally on your device.
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Frequently Asked Questions
What cron format does this support?
It supports the standard 5-field format (minute, hour, day-of-month, month, day-of-week) plus extended features like step values, ranges, and named months and days. It does not parse the optional 6-field (with seconds) Quartz format.
Why do I see different next runs in different timezones?
Cron schedules are evaluated in a specific timezone. The same expression fires at different absolute moments depending on the chosen timezone. Match the parser timezone to your scheduler to see the real run times.
How does it handle daylight saving time?
It uses IANA timezone data, so DST transitions are applied correctly. A daily 2:30am job will fire (or skip, or duplicate) the same way the real scheduler would handle the spring-forward and fall-back transitions.
What is the difference between day-of-month and day-of-week?
When both fields are restricted, most cron implementations treat them as OR: the job fires when either condition matches. The preview reflects this behavior.
Why is my expression invalid?
Common mistakes include too many or too few fields, out-of-range values (like minute 60), or unsupported syntax like ? or L on platforms that do not allow them. The error message points at the problem.
Is my data sent to any server?
No. Parsing runs entirely in your browser. Inputs are never uploaded, stored, or transmitted to any server.