As we all know IdentityServer is built with the concept of the central identity provider and it is supporting single sign-on by default as part of its main feature, but the single sign out is not coming as a part of inbuilt feature till IdentityServer3. Now they have added support for front-channel and back-channel specification for server-side clients in IdentityServer4. Here, I am going to explain how single sign out works using back-channel configurations.