Cron Expression Tester
Parse cron expressions, preview schedules, get human-readable descriptions
Cron Expression Tester validates a cron string (<code>0 */6 * * *</code>) and shows the next 10 scheduled runs. Supports standard cron + Quartz + non-standard predicates. Prevents typos in crontab.
Common Presets
Why teams trust us
How it works
Enter cron expression
Parse the schedule
Show 5 next run times
Why test cron expressions?
Cron expressions are easy to get wrong. One incorrect symbol and the job runs every minute instead of once a day. The tester decodes the expression and shows the next run times.
Expression Parser
Support for 5-component format: min, hour, day, month, day_of_week.
Next 5 Runs
Exact timestamps of next executions — verify the schedule is correct.
Time Zones
Calculation in UTC, Moscow, and server local time.
Human-readable Description
"Every Friday at 23:00" instead of 0 23 * * 5.
Who uses this
DevOps
cron check before deploy
Developers
task schedule debugging
Sysadmins
crontab audit
Business
critical job control
Common Mistakes
*/5 = every 5 minutes, 5 = only at minute 5 of the hour.Best Practices
@daily, @weekly — more readable and less error-prone than numbers.Add cron job monitoring
Heartbeat monitor: know when a cron job misses its run.
Sign up freeCron Expression Tester
Cron Tester lets you validate cron expressions and see upcoming task execution dates. Standard 5-field expressions are supported (minutes, hours, day of month, month, day of week), as well as special characters: * (any value), N-M (range), N/S (step), commas for lists.
Cron expressions use 5 fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), day of week (0-7). Special characters include * (any), / (step), - (range), and , (list). For example, */15 9-17 * * 1-5 means every 15 minutes during business hours on weekdays.
After configuring your cron schedule, set up heartbeat monitoring with dead man's switch to ensure cron jobs actually execute on time and don't silently fail.
Frequently Asked Questions
What is a cron expression?
A cron expression is a string of 5 fields (minute, hour, day of month, month, day of week) that defines a task execution schedule. Example: */5 * * * * — every 5 minutes. Used in Linux/Unix for automation.
How does cron syntax work?
Format: minute (0-59) hour (0-23) day (1-31) month (1-12) day_of_week (0-7). Special characters: * (any value), */N (every N), N-M (range), N,M (list). Example: 0 9 * * 1-5 — at 9:00 on weekdays.
What are common cron schedules?
Common schedules: * * * * * (every minute), 0 * * * * (every hour), 0 0 * * * (daily at midnight), 0 0 * * 0 (every Sunday), 0 0 1 * * (first day of every month).
How does timezone work in cron?
Cron uses the server timezone (usually UTC). To change it: set TZ=Europe/Moscow variable in crontab. Or recalculate time manually. Our tester shows next runs in the specified timezone.
How to debug a broken cron job?
Check: 1) crontab -l shows the task, 2) script has execute permissions, 3) file paths are absolute (cron does not use PATH), 4) redirect output: >> /tmp/cron.log 2>&1, 5) set up heartbeat monitoring.
Related guides
Longer-form reading on this topic from the knowledge base.
Dead man's switch for cron
Each job pings a URL — if it stops, you get alerted. Works for backups, cron, CI pipelines.