QR codes are added to the tickets of a ticket event by default, so you can use them to check people in at the door with the Confetti Check-In app. The QR codes are unique for each attendee and can lead to the information that they entered when signing up for the event.
QR codes on tickets can also be used if you have different Scanning sessions, for example used by partners on your event, as an easy way to collect contacts and information about the attendees.