Cron Expression Builder — Generate & Validate Cron Expressions

A cron expression is a compact scheduling notation: five space-separated fields — minute, hour, day-of-month, month, day-of-week — that define when a job should run. The notation was introduced in the Unix V7 cron daemon in 1979 and is now the universal scheduling language for Linux crontabs, GitHub Actions scheduled workflows, Kubernetes CronJobs, Vercel and Netlify functions, GitLab CI pipelines, and most cloud platform schedulers.

Reading a cron expression like 0 */6 * * * is easy once you know the field order, but writing one from intent — "I want this job to run every weekday at 9 AM" — requires knowing both the field order and the syntax for ranges, steps, and lists. This builder removes that friction: click chips to express your intent, and the corresponding expression is generated live. The output bar updates after every chip click so you see the result before copying anything.

Builder mode

Seven common preset chips at the top cover the most-used schedules: every minute, every 5 minutes, hourly, daily at midnight, weekdays at 9 AM, first of the month, and January 1st. Below them, a five-field chip grid lets you compose any expression chip by chip. Each field shows a live badge with its current value. For values not covered by the preset chips, every field has a Specific… input that accepts the full cron syntax: comma-separated lists (0,15,30), ranges (8-18), and step expressions (*/5).

Parser mode

Paste any five-field cron expression and the tool decodes it: the plain-English description appears immediately, the five-field chip grid highlights to reflect the parsed values, and the next five fire times are computed. Use this to audit a cron expression from a config file or a colleague's code before deploying it.

Next fire times

The fire times panel computes the next five moments the expression would trigger, starting from now. All computation uses the JavaScript Date API — no server call, no rounding error from timezone conversion. Toggle between UTC and your local timezone to see how the schedule maps to your workday.

The 5-field standard vs the 6-field Quartz variant

Some frameworks (Spring, Quartz, AWS EventBridge) use a six-field format that adds a seconds field at position zero. The POSIX 5-field format — which this tool supports — is what crontab, GitHub Actions, Kubernetes CronJob, Vercel, and Netlify use. If your platform requires a seconds field, check its documentation; pasting a 6-field expression here will be flagged as invalid because it has too many fields.