Introduction: Single Sign-On (SSO) is an authentication technique where the user uses one set of login credentials to access multiple web applications. About Platform: . Asp.net core MVC . Microsoft Identity Login . Dotnet core 2.2 . SQL LocalDB Core Concept: In the dotnet core, by sharing authentication cookie we can achieve SSO for the subdomains. A subdomain is a domain which part of another domain. Additional name prefixed to a domain that URL can be a subdomain. For example " http://testmyapp.com/ " is a domain, its subdomain looks like " http://mobile.testmyapp.com ". Create MVC Application & LocalDB Setup To IIS & IIS Hosting: Create an Asp.net MVC Core application by selecting a login individual user template from a visual studio. For this application use, LocalDB as a database then host this application to local IIS, bind "http://testmyapp.com" as domain and "http://mobile.testmyapp.com" as a domain to test