The cron expression for every 30 minutes

To run a job every 30 minutes, use */30 * * * *. Read aloud it means: At every 30th minute.

Field by field: minute */30 — every 30th minute; hour * — every hour; day of month * — every day-of-month; month * — every month; day of week * — every day-of-week.

Drop the expression into a crontab, a CI schedule, or anything else that speaks standard five-field cron syntax. The times above are in your local timezone — most cron daemons run in the server's timezone, so mind the difference when it matters.