IdentityServer is a free, open source OpenID Connect and OAuth 2.0 framework for ASP.NET Core. Founded and maintained by Dominick Baier and Brock Allen, IdentityServer4 incorporates all the protocol implementations and extensibility points needed to integrate token-based authentication, single-sign-on and API access control in your applications. IdentityServer4 is officially certified by the OpenID Foundation and thus spec-compliant and interoperable. It is part of the .NET Foundation, and operates under their code of conduct.