As attendees enroll for events, we can check if they happen to have something else going on at the same time by checking their calendar. If they do, we’ll provide a warning just before they complete the enrollment.
To enable this feature, go to Settings / Double-Booking Warning.
How it works
We use event organizer’s Google permissions to check free/busy of the attendee enrolling into the event. There may be a case where the attendee has Google Calendar permissions set to that the organizer is not allowed to do this API check. In that case, the Double-Booking Warning will be ignored since it cannot be checked.