OpenID Connect is an authentication protocol that builds on OAuth 2.0 to verify user identity. While OAuth handles authorization (what you can access), OpenID Connect adds an identity layer that answers a fundamental question: who is the person using this application?
Authentication meets authorization
OpenID Connect emerged because OAuth 2.0, while excellent for authorization, wasn't designed to verify identity. Developers were using OAuth in ways it wasn't intended, creating security vulnerabilities and inconsistent implementations. OpenID Connect formalized how to handle authentication on top of OAuth's authorization framework.
The result is a protocol that lets websites and applications authenticate users across other websites and apps without managing password files themselves. For application developers, it provides a secure, verifiable answer to who is currently using their service. For users, it means fewer passwords to manage and more consistent security across services.
How OpenID Connect works
When you use OpenID Connect to sign in to an application, you're redirected to an identity provider (like Google, Microsoft, or your organization's authentication server). You authenticate with that provider, which then sends the application an ID token containing verified information about your identity.
The ID token is a JSON Web Token (JWT) that includes claims about you, your unique identifier, when you authenticated, and potentially additional information like your email address or name. The application can verify this token cryptographically to confirm it came from the trusted identity provider and hasn't been tampered with.
This process happens alongside OAuth's authorization flow. The application receives both an ID token (proving who you are) and an access token (granting permission to access specific resources). The two protocols work together seamlessly.
Benefits for users and developers
OpenID Connect delivers significant benefits for everyone involved. Users get a simpler, more secure authentication experience. Rather than creating yet another account with another password, they can use credentials they already trust. The identity provider handles the complexity of secure authentication, including features like multi-factor authentication.
For developers and organizations, OpenID Connect eliminates the burden of storing and managing passwords. This can reduce risk by avoiding stored passwords. It also reduces legal and compliance complexity, since organizations aren't custodying sensitive authentication data.
The protocol is interoperable by design. An application built to support OpenID Connect can work with any compliant identity provider, from consumer services like Google to enterprise systems like Microsoft Azure AD to government identity providers.
OpenID Connect and digital identity
The OpenID Foundation, which develops and maintains OpenID Connect, has extended its work into verifiable digital credentials through OpenID for Verifiable Credentials (OpenID4VC). These specifications, including OID4VCI for credential issuance and OID4VP for credential presentation, define how verifiable digital credentials move between issuers, holders, and verifiers.
This extension is significant because it bridges familiar authentication infrastructure with emerging digital identity systems. Developers who already understand OAuth and OpenID Connect can apply that knowledge to implement verifiable credential flows. Organizations can build on existing investments in identity infrastructure rather than starting from scratch.
OpenID Connect in practice
OpenID Connect is widely deployed across consumer and enterprise applications. When you see "Sign in with Google" or similar options, you're typically using OpenID Connect. Enterprise environments use it for employee authentication across cloud services and internal applications.
Government implementations increasingly adopt OpenID Connect for citizen-facing services. State agencies implement identity gateways that support OpenID Connect for standards-based authentication, enabling secure token exchange, federated identity management, and compliance with identity architecture requirements. This standardization makes it easier to deliver unified, secure access to government services while maintaining interoperability across agencies and jurisdictions.
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