*/20 * * * * — what this cron expression means
The cron expression */20 * * * * runs every 20 minutes. Here is the field-by-field breakdown and what it means in plain English.
What */20 * * * * means
It runs every 20 minutes, at :00, :20 and :40 past every hour.
Field by field
minute=*/20 (a step: 0, 20, 40), hour/day/month/day-of-week all * (every).
72 times a day — three times per hour, around the clock.
When it runs next
Next run: the next matching time for */20 * * * *.
FAQ
How often is */20 * * * *?
Three times an hour: at :00, :20 and :40 — 72 runs per day.
Does */20 start at the top of the hour?
Yes. Steps count from 0, so the first run each hour is at :00.