Signout Support
When a user signs out of IdentityServer it is possible that client applications that the user has signed into want to be notified that the user is no longer logged in.
IdentityServer supports two styles of signout notifications. These styles coorespond to two (of the three) different OpenID Connection session management specifications: the session management and the HTTP-based logout specifications. One is designed for client-side JavaScript-based applications, and the other is designed for server-side web applications (ASP.NET, etc).
More info for support in IdentityServer for each can be found here: