Keycloak is a battle-tested open-source identity and access management solution. It lets you connect multiple identity providers—OAuth2, OpenID Connect, SAML—into one smooth login flow. That’s Identity Federation: linking trust between systems so users log in once and get access everywhere they need.
The power here is in centralization. Without federation, each app maintains its own user store, creates its own password headaches, and handles its own session management. With it, Keycloak becomes the hub. It brokers authentication requests to identity providers like Google, Azure AD, Okta, or your corporate LDAP. Your applications never handle credentials directly. They only trust the tokens Keycloak issues.
Configuring Identity Federation in Keycloak is straightforward. Add a new Identity Provider in the admin console. Choose the protocol—OpenID Connect, SAML—and enter the provider's metadata. Map identity provider attributes to Keycloak’s internal user model. Enable Just-In-Time user provisioning so accounts are created on first login. You can tweak flows for conditional authentication and required actions, enforce multi-factor authentication policies, or even chain providers together.