/ˌoʊ-pən-aɪ-di kəˈnɛkt/
n. “One login to rule them all… with modern flair.”
OpenID Connect is an authentication protocol built on top of the OAuth 2.0 framework. It allows clients—typically web and mobile applications—to verify the identity of a user based on the authentication performed by an identity provider (IdP) and to obtain basic profile information about that user in a secure and standardized way.
Unlike its predecessor, SAML, which is largely XML-based and enterprise-focused, OpenID Connect uses modern JSON-based tokens called ID Tokens, which are digitally signed JWTs (JSON Web Tokens). These tokens convey verified user information, such as username, email, and other attributes, enabling seamless Single Sign-On (SSO) across multiple services.
The typical OpenID Connect flow starts with the client redirecting the user to the identity provider for authentication. After the user authenticates, the IdP returns an ID Token and optionally an access token to the client. The ID Token proves the user’s identity, while the access token can authorize requests to protected APIs. This dual-token approach differentiates OpenID Connect from pure OAuth 2.0, which only handles authorization and leaves authentication ambiguous.
OpenID Connect has become the go-to protocol for modern applications because of its simplicity, security, and JSON-friendly design. It supports mobile, web, and API-based workflows, making it compatible with cloud services, social login providers, and enterprise identity systems. It integrates smoothly with OAuth 2.0 for delegated access while maintaining robust authentication guarantees.
Security is paramount. ID Tokens are signed and optionally encrypted, and HTTPS is required for all communications. Nonces, state parameters, and token validation rules prevent replay attacks, token substitution, and session hijacking. Developers must implement token verification correctly to avoid vulnerabilities—a misstep here can compromise the entire authentication flow.
In practice, OpenID Connect allows a user to log into a new web app using their Google, Microsoft, or other OpenID-enabled account. The client app doesn’t store credentials—it relies on the ID Token from the identity provider. This reduces password fatigue, centralizes security, and allows users to move across apps seamlessly.
Compared to SAML, OpenID Connect is lighter, JSON-native, and API-friendly, though SAML remains dominant in large enterprises. Together, these protocols provide a spectrum of options for modern and legacy Single Sign-On (SSO) implementations.
Today, OpenID Connect underpins millions of logins across cloud applications, consumer services, and mobile platforms. It’s not just an evolution of identity management—it’s a practical toolkit for making authentication seamless, secure, and developer-friendly in an era dominated by web and mobile apps.