.NET already has an identity platform (ASP.NET Identity) that provides authentication/authorization with various backends. IdentityServer is a token server that

.NET already has an identity platform (ASP.NET Identity) that provides authentication/authorization with various backends. IdentityServer is a token server that speaks OAuth/OIDC and provides federation to other user directories (ASP.NET Identity or Azure Directory or anything else). IdentityServer4 is still open-source and available. There's a new version by Duende with commercial licensing, or various alternatives like OpenIddict [1]. OAuth/OIDC is a well-supported standard so you can also use servers in other languages like Ory [2]. Microsoft's team did consider making their own token server but there was considerable pushback from the community because it would have a negative effect on open-source, and wouldn't add anything new compared to existing projects while taking resources from other framework features. 1. https://github.com/openiddict/openiddict-core https://github.com/openiddict/openiddict-core 2. https://www.ory.sh/open-source https://www.ory.sh/open-source