Every Universe website comes with a free subdomain that looks like yourname.univer.se. Sometimes this has been referred to as a username. Often Sometimes we have seen it referred to as a domain. It is most often referred to correct as a subdomain. Whatever you want to call it, it is an address for your website on the internet.

You selected your subdomain when you created your website. You can change your subdomain anytime from Site Settings.

If you are wondering about usernames because you are trying to login. Universe does not use usernames as a login method. Universe logins work with email and password or through Sign in with Apple. Contact support if you need help logging into your account.