| Identifier Type | Format Example | Uniqueness Requirement | | :--- | :--- | :--- | | | user@domain.com | Must be confirmed & unique per account | | Mobile Phone Number | +1 555 123 4567 | Must be verified via SMS or call | | Username (Custom URL) | username or facebook.com/username | Globally unique across Facebook | | Alternate Email | backup@domain.com | Must be attached to the same profile |
If you want, I can: