IdentityServer is described as 'An open-source, standards-compliant, and flexible OpenID Connect and OAuth 2.0 framework for ASP.NET Core'. There are nine alternatives to IdentityServer for a variety of platforms, including Online / Web-based, Self-Hosted solutions, SaaS, Windows and Linux. The best alternative is Keycloak, which is both free and Open Source. Other great apps like IdentityServer are Auth0 (Freemium), Okta (Freemium), Ory (Free, Open Source) and openiddict (Free, Open Source).
You can connect any application (written in any language or on any stack) to Auth0 and define its Connection, the method used to authenticate the users of that application: • Custom credentials: username + passwords • Social network logins: Google, Facebook, Twitter...
Ory builds cloud-native authentication (login), authorization (permission), delegation (OAuth2, OpenID Connect), and user management software. You can deploy what you need yourself or use the Ory Cloud Platform and get started in minutes.
OpenIddict aims at providing a versatile solution to implement an OpenID Connect server and token validation in any ASP.NET Core 2.1, 3.1 and 5.0 application, and starting in OpenIddict 3.0, any ASP.NET 4.x or OWIN application too.
authentik is an open-source identity provider focused on flexibility and versatility. - Easy to Use: Identity made easy. authentik makes single-sign on (SSO), user enrollment, and access control simple.