While Community certainly includes a fully functional membership system using ASP.net Forms Authentication, sometimes another solution is needed. If your customers already have accounts in another application in your environment, it may be undesirable to make them create separate accounts specifically for your community, and may lower adoption rates and participation. To adapt to this, Community also provides integration points to allow authentication control (login, logout, and registration) by a third party system, a process known as Single Sign-On (SSO).
Some pre-made clients exist already in Community. Here we provide an overview of those plugins.
Managing authentication can also be done via OAuth. Here we provide a sample implementation of OAuth authentication using Open ID Connect.
If you need to share authentication from an application that doesn't use ASP.net, you'll need to do it via Cookie Authentication.