Free Cron Expression Builder & Tester Online
Write, parse, and validate any standard 5-field cron schedule. See the next five execution times, get a plain-English description, and ship your CI, GitHub Actions, or Kubernetes CronJob with confidence.
Valid schedule
Every 5 minutes
- Mon, May 11, 2026, 11:10 PM2026-05-11T23:10:00.000Z
- Mon, May 11, 2026, 11:15 PM2026-05-11T23:15:00.000Z
- Mon, May 11, 2026, 11:20 PM2026-05-11T23:20:00.000Z
- Mon, May 11, 2026, 11:25 PM2026-05-11T23:25:00.000Z
- Mon, May 11, 2026, 11:30 PM2026-05-11T23:30:00.000Z
Quick Presets
Next 5 Fire Times
Computed from your local clock so you can immediately verify whether the schedule lines up with your intent — no mental math, no surprises in staging.
Per-Field Validation
If any of the five fields is invalid, we tell you which one and why. Catches off-by-one ranges, illegal steps, and month/weekday name typos.
12 Common Presets
One-click templates for the schedules you actually use — every 5 minutes, hourly, daily at 9, weekdays, monthly-on-the-first, quarterly, yearly.
100% Client-Side
Parsing, validation, and next-fire calculation all run in your browser. Your scheduling logic stays local — no server logs, no analytics on the expression.
The Engineer's Cron Expression Reference
Cron is one of the few UNIX-era tools that has aged into a true universal standard. Whether you are wiring a GitHub Actions workflow, deploying a Kubernetes CronJob, writing a Vercel Cron trigger, or scheduling a recurring AWS Lambda, the cron string is the lingua franca. Yet the syntax is famously easy to get wrong — a single off-by-one in the day-of-week field can mean your nightly backup quietly fails for a month. Our Free Online Cron Expression Builder & Tester exists to close that gap: paste any expression, see exactly when it fires next, and ship without second-guessing.
Pair this tool with our Timestamp Converter to cross-check Unix-time job logs, and the UUID Generator to tag each scheduled job with a unique correlation ID for observability.
Cron Field Reference
| Position | Field | Allowed Values | Aliases |
|---|---|---|---|
| 1 | Minute | 0–59 | — |
| 2 | Hour | 0–23 | — |
| 3 | Day of Month | 1–31 | — |
| 4 | Month | 1–12 | JAN, FEB, … DEC |
| 5 | Day of Week | 0–6 (Sun=0) | SUN, MON, … SAT |
Special Characters You Must Know
Wildcard *
Matches every value in the field. * * * * * fires every minute, all the time.
List ,
Multiple discrete values. 0 8,12,17 * * * fires at 8 AM, noon, and 5 PM daily.
Range -
0 9-17 * * 1-5 fires at the top of every hour from 9 AM through 5 PM, weekdays only.
Step /
*/15 * * * * fires every 15 minutes: :00, :15, :30, :45. Combine with ranges: 10-50/10 means 10, 20, 30, 40, 50.
The Three Mistakes Engineers Always Make
1. Forgetting that GitHub Actions / Vercel run in UTC
Your "9 AM" schedule may actually run at 4 AM local. Always convert to UTC for cloud cron runners. Our builder shows local time so you can subtract your UTC offset before pasting into your workflow file.
2. The OR rule for day-of-month + day-of-week
0 9 1 * MON does NOT mean "9 AM on the 1st when it's a Monday" — it means "9 AM on the 1st OR 9 AM every Monday." If you need an AND, gate inside your job.
3. Sub-minute precision does not exist in standard cron
If you need to run every 30 seconds, standard cron cannot help. Use Quartz, systemd timers, BullMQ, or have a 1-minute job that schedules an inner 30-second loop.
A Reliable Cron Authoring Workflow
Start From a Preset
Pick the closest preset above and adjust. Saves you from blank-page cron syntax recall.
Verify Next 5 Fires
Confirm the upcoming run times match your intent — including any weekday / day-of-month edge case.
Convert to UTC if Needed
Use our Timestamp Converter to translate local times to UTC before pasting into cloud workflow files.
Tag the Job for Observability
Pair every scheduled run with a fresh UUID as the correlation ID. Future-you will thank present-you when debugging at 2 AM.