Cron expression for every 15 minutes

The expression */15 * * * * runs a job four times an hour — at :00, :15, :30 and :45 — every hour of every day. The */15 step counts from minute 0, and because 15 divides 60 evenly the quarter-hour spacing is exact and repeats cleanly at the top of each hour.

Fifteen minutes is a sweet spot for jobs that need to feel current without the noise of per-minute runs: syncing external data, sending batched notifications, or scraping a rate-limited API. It is frequent enough that a single missed run is rarely serious, and infrequent enough to keep logs readable.

To limit it to part of the day, add hour and weekday constraints — */15 8-18 * * 1-5 runs every 15 minutes from 8 AM to 6:59 PM on weekdays. If you want the quarter-hours of a single hour only, drop the step: 0,15,30,45 9 * * * is the explicit form for 9 AM.