Open Source SSO
Single sign-on becomes the thing every app in your company learns to trust, which makes it the hardest piece to ever replace - so the protocols it speaks matter more than its features, because standards like OIDC and SAML are your only clean exit path. The open source identity providers here implement those standards openly and run on your own infrastructure, so your directory and the trust every app places in it stay yours to move.
Keycloak
Open source identity and access management for adding authentication, user federation, and authorization
Authelia
Open-source SSO and multi-factor authentication portal for applications behind reverse proxies
authentik
Open-source identity provider for SSO with SAML, OAuth2/OIDC, LDAP, and RADIUS
Teleport
Identity-aware infrastructure access with short-lived certificates and audit across SSH, Kubernetes, databases, and RDP
Ory Hydra
OpenID Certified OAuth 2.0 and OpenID Connect server for SSO, API access, and machine-to-machine authorization
SuperTokens
Open-core user authentication with login, session management, and on-premises control of user data
ZITADEL
Open-source identity infrastructure for SSO, MFA, passkeys, OIDC, SAML, and SCIM
Casdoor
AI-first identity and access management platform with MCP gateway and web UI
Ory Kratos
API-first identity and user management for login, registration, recovery, verification, and profile flows