Using built-in authentication
If you don't use a centralized, external system for your users' identity, you can use built-in authentication to allow GitHub Enterprise Server to manage accounts and perform local authentication.
When you use the default authentication method, all authentication details are stored on your GitHub Enterprise Server instance.
When you use built-in authentication for GitHub Enterprise Server, you can invite people by email address to create a user account on your instance.
If you're using built-in authentication for your GitHub Enterprise Server instance, you can block unauthenticated people from creating new user accounts on your instance.