Sso

OpenID Connect (OIDC) is an authentication protocol built as a thin layer on top of OAuth 2.0, published by the OpenID Foundation in 2014. Where OAuth 2.0 defines how to delegate authorisation (granting access to resources), OIDC adds the missing authentication semantics: a standard ID token that proves who the user is, a UserInfo endpoint that returns standardised identity claims, and a discovery document that allows clients to configure themselves automatically from a single well-known URL. The separation is precise: OAuth 2.0 access tokens prove that a client is authorised to call an API; OIDC ID tokens prove that a specific user authenticated with a specific identity provider at a specific time. OIDC is the protocol behind virtually every “Sign in with Google / GitHub / Microsoft” flow, every SAML-to-modern-stack migration, and every Kubernetes service account token issued today — making it the dominant authentication federation standard in cloud-native infrastructure.