UlvixorCron Expression Generator
Build 5-field cron expressions using guided controls and ready-made templates, or paste an existing cron expression to get a plain-English description. Everything is calculated in your browser, with no external dependencies.
How it works
- In the 'Build' tab, pick a quick template or fill in the minute, hour, day-of-month, month, and day-of-week fields manually.
- The resulting cron expression and its plain-English description update in real time.
- In the 'Interpret' tab, paste any 5-field cron expression to see what it means, in plain English.
- If the expression has a syntax error, you'll see exactly which field and value caused the problem.
- Copy the final expression with one click to use in your crontab or task scheduler.
Use cases
- Set up scheduled tasks (cron jobs) on Linux servers without memorizing the syntax.
- Understand what a legacy cron expression does before modifying it.
- Schedule CI/CD workflows or serverless functions that use cron syntax (GitHub Actions, AWS EventBridge, Kubernetes CronJobs).
- Verify that a cron expression does exactly what you expect before deploying it to production.
Use cases
- Set up scheduled tasks (cron jobs) on Linux servers without memorizing the syntax.
- Understand what a legacy cron expression does before modifying it.
- Schedule CI/CD workflows or serverless functions that use cron syntax (GitHub Actions, AWS EventBridge, Kubernetes CronJobs).
- Verify that a cron expression does exactly what you expect before deploying it to production.
Common mistakes
- Mixing up the field order, for example putting the month before the day.The standard 5-field order is: minute, hour, day of month, month, day of week. The 'Build' tab avoids this mistake by using separate fields.
- Assuming day-of-month and day-of-week combine with 'AND' when both are restricted.Cron combines them with 'OR', not 'AND', whenever both fields have a value other than *. The tool explains this in the generated description.
- Forgetting that the time doesn't account for your personal time zone.The cron expression runs according to the time zone configured on the server or service, not yours. Check that setting separately.
Frequently asked questions
It supports standard 5-field expressions (minute, hour, day of month, month, day of week) with asterisks (*), exact numbers, ranges (a-b), steps (*/n or a-b/n), and comma-separated lists (1,15,30). It doesn't support text month or day names (JAN, MON), special characters like L, W, or # from dialects such as Quartz, or 6-field expressions with seconds.
Following standard cron behavior, when both fields have a value other than '*', the task runs if either condition is met (not both at once). The tool reflects this logic with the word 'or' in the description.
No. Both building and interpreting cron expressions happen entirely in your browser using JavaScript, with no external library or server calls.
The tool doesn't apply any time zone: the hour and minute fields are interpreted exactly as you type them. The time zone in which the task actually runs depends on how the system or service running the cron job is configured (for example, UTC in many CI/CD environments), not on this tool.
Alternatives
Sites like crontab.guru offer a similar feature in English. This tool adds a guided 'Build' mode with templates and a plain-English description, useful if you don't want to memorize the syntax.