You can specify that all or some of your event tickets are only open to attendees over 21 by setting a 21+ age limit on your tickets tickets.
21 and Over Checkbox
You will need to check the Is this ticket 21 years and older only? checkbox for EACH ticket that you would like to only open to attendees over 21. To do this in your event dashboard, navigate to Tickets >> Setup.
For simple tickets, click the Actions dropdown on the right-hand side of the ticket and select More Settings:
If you have enabled Advanced Tickets (under Tickets >> Advanced Tickets), click the Edit Icon on the right-hand side of the ticket:
Click the 21 and over checkbox, and click Save:
Turn on Individual Ticket Information Collection
In order to make sure each ticket holder is over 21, you must enable Individual Ticket Information. To do this, navigate to Tickets >> Information Collection, click the Edit Icon for the selected ticket/ticket group, and turn on the Individual Ticket Information toggle:
If you choose to require that either Age OR Date of Birth under Individual Ticket Information, each ticket holder will have to enter an age or date of birth that is over 21.
When enabled, the personal information collection page will show an error if someone under 21 (based on the age and/or date of birth entered) tries to buy a 21+ ticket:
If you select to make Age and Date of Birth either Optional or Not Shown in the Individual Ticket Information collection, each ticket holder will be required to check a checkbox to confirm this person is at least 21 years old:
When a ticket holder tries to continue through the purchase path without checking the 21 years old checkbox, they will receive and error: