Introduction: In Part-1 we have implemented SSO with sharing authentication cookie between domain and subdomain binds to an MVC application. Now we implement the sharing authentication cookie between two different applications which runs under another application in IIS Server. For example, ASP.NET Core MVC application is client application shares login cookie to the ASP.NET Core WEB API which is hosted under the MVC application as a child in IIS Server. To know more about child application runs under another application click here Core Concept: Sharing authentication Cookie between entirely two different applications, but one application runs under other applications in IIS. Create an MVC Application: Create an MVC application by following Part-1 , consider it is the main application for registering users and log-in to the application. Create WEB API Application: Now we have to create another application, which runs under the MVC application(created by following Step 1