Definition
Federation is the practice of accepting authentication from a trusted external identity provider — letting users sign in with their identity from another organization.
In more depth
Implementations: SAML federation (workforce SSO), OIDC federation (consumer + B2B SSO), InCommon (research-and-education federation), Open Banking federation.
The alternative to maintaining separate user accounts in every relying party. Foundational for B2B SaaS, partner access, and cross-organizational identity.
Want the work, not just the definition?