Cron Expression Generator

A cron expression is a compact string of five fields that tells a Unix or Linux scheduler exactly when to run a job. Originally introduced in the AT&T Bell Labs Version 7 Unix operating system, the cron daemon has become the universal standard for time-based task automation on servers, cloud platforms, and CI/CD pipelines worldwide.

Each expression consists of five space-separated fields representing, in order: minute, hour, day of month, month, and day of week. This cron expression generator lets you build and preview any schedule visually — no need to memorise numeric ranges or special-character syntax.

Understanding how the five fields combine is the key to writing reliable schedules. For example, the widely-used expression 0 2 * * * fires at exactly 2:00 AM every single day, while */15 * * * * fires every fifteen minutes around the clock. The generator on this page assembles the final expression in real time as you adjust each field, and translates it back into plain English so you can confirm the schedule before copying it into your crontab or cloud scheduler.

Each of the five fields in a cron expression accepts a specific numeric range, and any field can be replaced with a wildcard or a special-character expression. The table below summarises the allowed values for quick reference whenever you are writing or debugging a crontab entry.

When both day of month and day of week are set to specific values (not wildcards), the cron daemon fires the job when either condition is true — not when both are simultaneously true. Keep this OR behaviour in mind to avoid unintended double-executions.

Cron's power comes from four special characters that let you express complex repeating schedules in a single field. Mastering them turns a rigid five-number string into a highly flexible scheduling language.

• Asterisk (*) — Matches every possible value in a field. * * * * * runs every minute of every day.
• Comma (,) — Creates a list of discrete values. 0,30 * * * * fires at minute 0 and minute 30 of every hour, giving you a twice-per-hour schedule.
• Hyphen (-) — Defines an inclusive range. 0 9-17 * * 1-5 fires every hour from 9 AM to 5 PM on weekdays — ideal for business-hours monitoring jobs.
• Slash (/) — Specifies a step interval. */15 in the minute field means "every 15 minutes starting from 0", producing executions at :00, :15, :30, and :45. */6 in the hour field fires every six hours: midnight, 6 AM, noon, and 6 PM.

You can freely combine these characters within a single field. For instance, 0,30 */2 * * 1-5 fires at minutes 0 and 30 of every other hour, but only on weekdays. Building up complex expressions step by step in this cron expression generator — checking the plain-English description after each change — is the safest way to get exactly the schedule you need.

Certain cron schedules appear so frequently in production environments that they have become de-facto standards. Knowing these patterns by heart speeds up configuration and reduces the chance of typos in critical scheduling jobs.

These patterns are available as quick-select presets in the generator above. Click any preset to populate all five fields at once, then fine-tune individual fields as needed for your specific use case.

Cron expressions power an enormous range of automated tasks in modern infrastructure. Understanding which schedule pattern fits each use case helps you write more reliable and efficient jobs from the start.

• Database backups — A nightly 0 2 * * * job runs a full database dump at 2 AM when traffic is lowest, minimising performance impact.
• Log rotation and cleanup — Weekly jobs using 0 0 * * 0 compress old log files every Sunday, preventing disk exhaustion on busy servers.
• Email digests and reports — 0 8 * * 1-5 sends a morning business report to stakeholders at 8 AM every weekday.
• Cache invalidation — */5 * * * * refreshes a CDN or application cache every five minutes to keep data reasonably fresh without hammering the origin server.
• Health checks and monitoring — * * * * * runs a lightweight ping script every minute to detect downtime within 60 seconds.
• Monthly billing runs — 0 0 1 * * triggers invoice generation on the first of every month.
• Seasonal tasks — 0 9 1 1,4,7,10 * fires on the first day of each quarter for financial reporting or data archiving.

Cloud platforms such as AWS EventBridge, Google Cloud Scheduler, GitHub Actions, and Kubernetes CronJobs all accept standard five-field cron expressions, making the skills you develop with this cron expression generator directly portable across environments.