OAuth OIDC JWT: Roles and Relationships

July 9, 2026

OAuth OIDC JWT are distinct yet interconnected components crucial for modern authentication and authorization systems. OAuth 2.0 is an authorization framework defining how to grant access, while OpenID Connect (OIDC) is an authentication protocol built on top of OAuth 2.0, enabling single sign-on (SSO) and identity management. JSON Web Tokens (JWTs) are a compact, URL-safe means of representing claims between two parties, often used as access tokens in OAuth and always as ID tokens in OIDC to convey user identity and authorization details.

Differentiating OAuth, OIDC, and JWT Fundamentals

OAuth 2.0 functions as an authorization framework, defining how a client application can obtain limited access to a user's resources hosted by a service provider, without ever exposing the user's credentials to the client. For instance, when a user grants a photo editing application access to their Google Photos library, OAuth 2.0 facilitates this authorization. It is described in IETF RFC 6749 and 6750. In contrast, OpenID Connect (OIDC) is an authentication layer built directly on top of OAuth 2.0. OIDC extends OAuth's authorization capabilities to include identity verification, enabling clients to confirm the end-user's identity and obtain basic profile information. An example is the "Sign in with Google" feature, which uses OIDC to authenticate the user and provide their identity to the third-party application.

JSON Web Tokens (JWTs) serve as a compact, URL-safe method for securely transmitting information between parties as a JSON object. They are fundamentally a token format, not a protocol or framework. JWTs are commonly used as access tokens within OAuth 2.0 flows to convey authorization decisions and as ID tokens in OIDC to carry user identity claims. A JWT contains claims, which are statements about an entity (typically the user) and additional data. For example, an OIDC ID token, which is always a JWT, might contain claims such as the user's email address, name, and an aud (audience) claim specifying the recipient of the token. The structure of JWTs allows for digital signatures, ensuring the integrity and authenticity of the claims.

OAuth 2.0: The Authorization Framework

OAuth 2.0 is the industry-standard protocol for authorization, not authentication. Its primary function is to enable delegated authorization, allowing third-party applications (clients) to access protected resources on behalf of a user, without ever exposing the user's credentials to the client. This framework focuses on specific authorization flows to grant limited access. For example, when a user connects Zoom to Google Calendar, OAuth facilitates Zoom's access to calendar data without requiring the user to share their Google password with Zoom. The framework defines how access tokens are issued and used. These tokens represent the authorization granted by the user to the client application for specific actions, such as reading emails or accessing files. OAuth 2.0 is described in IETF RFC 6749 and 6750, and it provides various grant types (flows) tailored for different client types and use cases, ensuring API security and controlled access to resources. While OAuth 2.0 deals with what a client can do, it does not confirm who the user is; that role is reserved for authentication protocols like OpenID Connect.

OpenID Connect: Authentication on Top of OAuth

OpenID Connect (OIDC) is an authentication layer built directly upon the OAuth 2.0 framework, specifically designed to verify a user's identity. While OAuth 2.0 provides authorization—determining what a client application can access—OIDC adds the crucial element of authentication, confirming who the user is. This is achieved by extending OAuth 2.0's capabilities to include identity verification and the retrieval of basic user profile information.

A prime example of OIDC in action is the ubiquitous "Sign in with Google" feature. When a user clicks this button on a third-party website, OIDC facilitates a single sign-on (SSO) experience. The user is redirected to Google, authenticates themselves (if not already logged in), and then grants permission for the third-party application to receive their identity details. Google, acting as the identity provider, issues an ID token—always a JSON Web Token (JWT)—containing "claims" about the user, such as their name, email, and a unique identifier. This ID token is then securely passed back to the client application, allowing it to confirm the user's identity and log them in seamlessly. OIDC leverages OAuth 2.0's access tokens for authorization, but introduces ID tokens specifically for authentication, ensuring a robust and interoperable standard for identity management.

JSON Web Tokens (JWTs): The Universal Token Format

JSON Web Tokens (JWTs) are a compact, URL-safe means of representing claims between two parties. They are widely used as a token format to package and transmit these claims, serving distinct purposes within authentication and authorization protocols. In OpenID Connect (OIDC), ID tokens are always JWTs, conveying identity claims about the authenticated user, such as their name, email, and a unique identifier. This allows client applications to verify the user's identity and facilitate single sign-on (SSO). For instance, an OIDC ID token contains an aud (audience) claim, specifying the intended recipient of the token. Within the OAuth 2.0 framework, JWTs can also function as access tokens, enabling delegated authorization and securing API access. RFC 7523 details the use of JWTs as authorization grants within OAuth 2.0, where a JWT bearer token can be used in an access token request with a grant_type of "urn:ietf:params:oauth:grant-type:jwt-bearer". The structure of JWTs, which includes digital signatures, ensures the integrity and authenticity of the information they carry, making them a foundational element for identity management and API security in modern distributed environments.

Interoperability, Security, and Comparison with SAML

The combined use of OAuth 2.0, OpenID Connect (OIDC), and JSON Web Tokens (JWTs) forms a robust framework for modern identity management, providing both authorization and authentication. OAuth 2.0, as an authorization framework, defines how to grant access to resources, while OIDC builds on OAuth 2.0 to verify user identity and retrieve profile information, often using JWTs as ID tokens. JWTs, in turn, serve as a compact, URL-safe format for transmitting claims, ensuring data integrity through digital signatures. For instance, an OIDC ID token, always a JWT, contains an aud claim specifying the intended recipient, confirming its role in authentication. This interoperability allows for secure single sign-on (SSO) and API security, as the acr_values and max_age parameters in OIDC can signal required authentication strength or recency, enhancing security beyond basic access control.

In comparison to Security Assertion Markup Language (SAML), OAuth 2.0 and OIDC offer a more modular and REST-friendly approach. SAML is an XML-based protocol primarily used for authentication in enterprise environments, enabling SSO for applications like Google Workspace or Salesforce. While SAML can be complex and verbose, the OAuth/OIDC/JWT stack provides a streamlined, often JSON-based, alternative that is well-suited for distributed environments and mobile applications. The use of JWTs for both ID tokens in OIDC and potentially for access tokens within OAuth 2.0 (as detailed in RFC 7523 for JWT bearer grants) simplifies token handling and verification across different services.

Frequently Asked Questions

What is the difference between OAuth and OIDC?

OAuth 2.0 is an authorization framework that allows delegated access to resources, while OpenID Connect (OIDC) builds on OAuth 2.0 to provide an identity layer for user authentication and to retrieve basic profile information. OIDC uses OAuth 2.0's authorization capabilities but adds specific features for identity verification.

Can OAuth work without OIDC?

Yes, OAuth 2.0 can work independently without OIDC. OAuth 2.0's primary function is authorization, enabling a third-party application to access protected resources on behalf of a user, without necessarily verifying the user's identity itself.

Is JWT used for authentication or authorization?

JWTs are used for both authentication and authorization. In OIDC, ID tokens are always JWTs and are used for authentication, conveying identity claims. Within OAuth 2.0, JWTs can also function as access tokens for authorization, granting access to specific resources.

What is an ID token vs. an access token?

An ID token (always a JWT in OIDC) is used for authentication, verifying the user's identity and providing claims about them. An access token, often a JWT in OAuth 2.0, is used for authorization, granting permission to access specific protected resources.

How do OAuth, OIDC, and JWT work together?

OAuth 2.0 provides the authorization framework, OIDC adds an authentication layer on top of OAuth 2.0 to verify user identity, and JWTs serve as the universal token format for both ID tokens (in OIDC) and potentially access tokens (in OAuth 2.0), carrying claims securely.

When should I use OAuth vs. SAML?

OAuth 2.0 and OIDC offer a modular, REST-friendly approach well-suited for modern web and mobile applications, focusing on delegated authorization and identity. SAML is an XML-based protocol primarily used for enterprise single sign-on (SSO) in more traditional, often browser-based, environments.

Conclusion

The synergy between OAuth 2.0, OpenID Connect, and JSON Web Tokens forms a robust and flexible framework for modern authentication and authorization. Understanding their individual roles and how they interoperate is crucial for building secure and scalable applications. This powerful combination streamlines identity verification and resource access across diverse digital environments.

Sources & References

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