Keycloak - Open Source Identity and Access Management for modern Applications and Services.

IdentityServer - An open-source, standards-compliant, and flexible OpenID Connect and OAuth 2.x framework for ASP.NET Core

DbProtect - Trustwave DbProtect is a highly scalable database security platform that helps organizations secure their relational databases and big data stores, both on premises and in the cloud.

ASP.NET Identity - ASP.NET Identity is a membership-based software system designed for the authentication and authorization of the users via building an ASP.NET application.

Okta - Enterprise-grade identity management for all your apps, users & devices

DotNetOpenAuth - DotNetOpenAuth is a free-to-use compiled library that comes with the real support to your site visitor to login with the help of openIDs via getting control of the ASP.NET control onto the page.