Cron Expression Builder

About the Cron Expression Builder

A cron expression is a string with five space-separated fields that define a repeating schedule for a task. Cron is used by Linux/Unix schedulers, Kubernetes CronJobs, CI/CD pipelines, cloud functions, and most task queue systems. Getting the syntax right can be tricky — this tool makes it easy to build, validate, and understand any cron expression.

Cron expression syntax

The five fields, from left to right, are:

Field syntax

Each field supports four types of value:

• * — wildcard, matches every value in the range
• 5 — literal value, matches only that value
• 1-5 — range, matches every value from 1 to 5 inclusive
• 1,3,5 — list, matches 1, 3, and 5 only
• */15 — step, matches every 15th value (0, 15, 30, 45 for minutes)

Builder vs. raw mode

The builder mode provides a separate input for each of the five fields, which is helpful when you are constructing an expression from scratch or learning the syntax. Raw mode lets you type or paste a complete expression and see the human-readable description update instantly. Both modes are kept in sync — switching between them preserves the current expression.

Next run preview

The tool calculates the next five scheduled run times using your browser's local timezone. This is useful for verifying that a schedule fires when you expect — particularly important when a cron job runs on a server in a different timezone. Remember: most cron daemons and Kubernetes CronJobs run in UTC by default, so consider converting your local times accordingly.

Common use cases

• Configuring a Kubernetes CronJob to run a batch process at a specific time
• Setting up a CI/CD scheduled pipeline (e.g. nightly builds, weekly reports)
• Debugging an existing cron expression that is firing at unexpected times
• Converting a plain-English schedule into a valid cron expression
• Verifying that a step expression (e.g. every 6 hours) covers the expected time slots

Privacy

This tool runs entirely in your browser. No cron expressions or schedule data are sent to any server. Learn more about how Dev-Utilities handles privacy.