Guidelines for creating a custom username or screen name on Facebook
When you create a custom username for your Page or profile, keep in mind:
- You can only have one username for your Page or profile, and you can't have a username that is already being used.
- Usernames can only contain alphanumeric characters (A–Z, 0–9) and periods ("."). They can't contain generic terms or extensions (.com, .net).
- Usernames must be at least 5 characters long.
- Periods (".") and capitalization can't be used to differentiate usernames. For example, johnsmith55, John.Smith55 and john.smith.55 are all considered the same username.
- Usernames shouldn't impersonate someone else.
- Your username must adhere to the Facebook Terms.
Usernames for Pages
Keep in mind that you must be an admin to create or change the username for a Page.
You may not be able to immediately create a username for a new Page if you’ve recently created several new Pages. A Page’s username can also be removed because of inactivity.