Cron is the scheduler that runs tasks on Linux servers, cloud functions and many CI systems. Its syntax — five fields that say when something should run — is powerful but famously easy to get wrong. One misplaced asterisk and a job meant for midnight fires every minute instead.
This builder removes the guesswork. Pick a value for each field and it assembles a valid expression, explains it in plain English, and shows the next five times it will actually run so you can confirm it behaves the way you expect.
What does 0 9 * * 1 mean? It runs at 09:00 on Mondays — minute 0, hour 9, every day of month, every month, weekday 1 (Monday).
What does */15 in the minute field mean? Every 15 minutes — the step value after the slash repeats that often.
Do day-of-month and day-of-week combine? If both are set, the job runs when either matches, which surprises people. Keep one of them as * unless you know you want that.