Keycloak - Open Source Identity and Access Management for modern Applications and Services.
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
authentik - authentik is an open-source identity provider focused on flexibility and versatility.
FusionAuth - FusionAuth is a CIAM platform that is 100% free for unlimited users.
Authelia - Authelia is an open-source authentication server providing SSO and two-factor for your applications running behind NGINX.
Pomerium - Pomerium is an identity-aware proxy that enables secure access to internal applications.