Cron Expression Validator - Test & Explain
Validate your cron expressions and see when they'll run next. Get human-readable explanations of cron syntax and preview upcoming execution times.
Understanding This Tool
What It Does
Validate and explain cron expressions used in scheduled tasks. This tool checks if your cron syntax is correct and shows when the job will run.
Understanding the Results
- Cron Expression: The schedule syntax being analyzed
- Validity: Whether the expression is syntactically correct
- Description: Human-readable explanation of the schedule
- Next Run Times: When the scheduled job will run next
- Frequency: How often the job executes
Common Use Cases
- Scheduled Tasks: Configure cron jobs for Linux/Unix systems
- Cloud Schedulers: Set up schedules in AWS, Azure, GCP
- Testing: Verify cron syntax before deployment
- Documentation: Understand existing cron schedules
- Troubleshooting: Debug scheduling issues
Pro Tips & Best Practices
- Five Fields: Cron uses minute, hour, day, month, day-of-week
- Asterisk: * means all possible values for that field
- Common Patterns: Daily at midnight: 0 0 * * * | Every hour: 0 * * * *
Frequently Asked Questions
Standard cron uses five fields: minute, hour, day of month, month, and day of week. Each field controls when the job runs, from left to right.
An asterisk means every allowed value for that field. For example, 0 * * * * runs at minute 0 of every hour, every day.
Use 0 0 * * *. This means minute 0, hour 0 (midnight), on every day of the month, every month, and every day of the week.
Common causes include server timezone differences, invalid field values, missing cron daemon/service, or using the wrong number of fields for your platform.
Most Linux and Unix systems use five-field cron syntax, but some schedulers add seconds or use different field orders. Always verify against your platform's documentation.
Frequently Asked Questions
What do the five fields in a cron expression mean?
Standard cron uses five fields: minute, hour, day of month, month, and day of week. Each field controls when the job runs, from left to right.
What does an asterisk (*) mean in cron syntax?
An asterisk means every allowed value for that field. For example, 0 * * * * runs at minute 0 of every hour, every day.
How do I schedule a job to run daily at midnight?
Use 0 0 * * *. This means minute 0, hour 0 (midnight), on every day of the month, every month, and every day of the week.
Why does my cron job not run when I expect it to?
Common causes include server timezone differences, invalid field values, missing cron daemon/service, or using the wrong number of fields for your platform.
Is cron syntax the same everywhere?
Most Linux and Unix systems use five-field cron syntax, but some schedulers add seconds or use different field orders. Always verify against your platform's documentation.
Last reviewed:
How this tool works: This tool runs in your browser and on our server in real time. Depending on the tool, results are computed directly from the input you provide or retrieved from live, authoritative data sources at the moment you run a lookup. We do not sell your data, and your lookups are kept private — any history shown here is stored only on your device.