0 * * * * — every hour, on the hour

Answer

0 * * * * runs once an hour, at minute 0: 00:00, 01:00, 02:00 and so on, 24 times a day. @hourly means exactly the same.

At minute 0 past every hour.

0
Minute (0-59)
At minute 0 (on the hour)
*
Hour (0-23)
Every hour
*
Day of month (1-31)
Every day (no restriction)
*
Month (1-12 or JAN-DEC)
Every month
*
Day of week (0-7 or SUN-SAT (0 and 7 = Sunday))
Every day (no restriction)

24 runs a day on average168 a week364 of the next 364 days have a run

Hours of the week (darker = more runs)

The next 52 weeks, one square per day

What to know

The 0 matters. Writing * 0 * * * instead gives the opposite: every minute, but only during the midnight hour (60 runs from 00:00 to 00:59).

To run hourly at a quieter moment, pick a different minute: 17 * * * * runs at 17 past every hour.

17 * * * *
hourly at 17 pastAt minute 17 past every hour.
0 8-18 * * 1-5
hourly during working hours on weekdaysAt minute 0 past every hour from 08:00 to 18:00 on Monday through Friday.

* * * * * is every minute, not every hour: the minute field must be a fixed number for hourly.
Many scheduled jobs across the internet fire at :00. If the job calls an external API, an odd minute avoids the rush.