OIDC
also: OpenID Connect
OpenID Connect (OIDC) is an authentication protocol built on top of OAuth 2.0 that enables users to log in to applications using credentials from an identity provider, with the identity provider returning verified identity information.
OIDC extends OAuth 2.0 by adding an identity layer, allowing applications to verify who a user is and obtain basic profile information. While OAuth 2.0 focuses on authorization (what you can do), OIDC adds authentication (confirming who you are).
In a typical OIDC flow, a user clicks "Login with Google" or similar on an application. The app redirects them to Google's identity provider, where they authenticate. Google then returns a cryptographically signed token (ID token) containing the user's identity claims such as email and name, which the application trusts and uses to log the user in.
OIDC is widely used in modern Linux environments, cloud platforms, and containerized systems for single sign-on (SSO) and federated identity management, often integrated with tools like Kubernetes, GitLab, and Keycloak.