Custom Fields are used to collect various kinds of information from your participants as they enter tournaments on Battlefy. They have a very similar functionality to customizing a google registration form for tournament entry.
Simply click the "plus" button to add additional custom fields to your registration process
You can also toggle your custom fields to be public to everyone, or only visible to the organizer by clicking on the "eyeball toggle"
Some Use Cases:
Shadowverse organizers set custom fields for deck registration at the start of the tournament for conquest mode
Some Organizers set a custom field for paypal email (toggled to private) for payouts after tournaments are done
Some Organizers set a custom field to get a sense of where their players have heard about their tournament from: "Where did you hear about this tournament?"
Editing Custom Fields directly affect player registration. After the Tournament is Published, Custom Fields cannot be edited and new custom fields (or deleting other fields) can only be done after first unpublishing the tournament.