About this tool

Cron Expression Generator is a small, focused utility for anyone who has ever stared at a line like */15 9-17 * * 1-5 and wondered exactly when it fires.

I’m Marcio, an independent developer‑tools builder. I built this because the moment you only touch crontab a few times a year, the syntax slips out of your head – and the one rule everybody forgets (the day‑of‑month versus day‑of‑week OR behaviour) is exactly the one most likely to schedule a job at the wrong time. A tool that decodes the expression into plain English and shows the actual next run times removes the guesswork.

How it works

Everything runs in your browser with plain JavaScript. When you type an expression, the page parses all five fields, applies the real Vixie‑cron matching rules, and computes the upcoming run times against your device’s clock. Nothing is sent to a server, there is no account, and there are no uploads – your schedules stay on your machine.

Accuracy

The parser implements standard five‑field cron: wildcards, ranges, lists, steps and named months and days, plus the correct OR behaviour when both day fields are set. For non‑standard dialects such as Quartz or cloud schedulers, see the platform comparison. If you spot a case the tool reads incorrectly, I’d genuinely like to hear about it – please get in touch.

This site is reader‑supported and may display advertising to cover hosting; it does not change how the tool behaves. See the privacy policy for details.