Keycloak is an open source identity and access management solution. Keycloak offers features such as Single-Sign-On (SSO), Identity Brokering and Social Login, User Federation, Client Adapters, an Admin Console, and an Account Management Console.
SuperTokens is an open source alternative to Auth0. Add secure, hassle free authentication to your app in 1 day. SuperTokens enables startups to launch quicker and focus on their core product offering.
privacyIDEA is an open-source modular authentication system. Using privacyIDEA you can enhance your existing applications like local login, VPN, remote access, SSH connections, access to web sites or web portals with a second factor during authentication.