OAuth2 vs OpenID Connect: What are the differences?

1. Authentication vs Authorization: The key difference between OAuth2 and OpenID Connect lies in their primary focus. OAuth2 is primarily focused on authorization, allowing access to protected resources on behalf of the resource owner. On the other hand, OpenID Connect is mainly focused on authentication, providing identity information and verifying the identity of the resource owner.
2. Token Types: OAuth2 uses access tokens to authorize access to protected resources, which are typically short-lived and provide limited access rights. OpenID Connect, on the other hand, uses ID tokens to verify the identity of the user and provide additional user information. ID tokens are typically long-lived and contain more detailed user information.
3. Scopes and Claims: OAuth2 uses scopes to define the extent of access rights granted to an access token. These scopes can be used to define different levels of authorization for different resources. OpenID Connect extends OAuth2 by introducing claims, which provide more detailed user information and can be requested in addition to the access token.
4. Intended Use Case: OAuth2 is primarily designed for securing API access and enabling third-party applications to access protected resources on behalf of the user. OpenID Connect, on the other hand, is designed for authentication and single sign-on (SSO) scenarios, enabling users to authenticate once and then access multiple applications without the need to reauthenticate.
5. Token Validation: When validating an access token, OAuth2 focuses on validating the token's integrity and checking its scopes for authorized access. OpenID Connect, in addition to validating the access token, also verifies the ID token's signature and signature validation claims, ensuring the authenticity and integrity of the authentication information.
6. Standardization and Interoperability: OAuth2 is a well-established and widely adopted industry standard for authorization, supported by various frameworks and platforms. OpenID Connect builds on OAuth2 and provides a standardized solution for authentication, ensuring interoperability between different identity providers and relying parties.

In summary, OAuth2 focuses on authorization for accessing protected resources, while OpenID Connect focuses on authentication and identity verification. OAuth2 uses access tokens for authorization, while OpenID Connect uses ID tokens for authentication and providing user information. The scopes and claims in OAuth2 and OpenID Connect provide different levels of access rights and user information. OAuth2 is designed for API access and third-party applications, while OpenID Connect is designed for authentication and single sign-on scenarios. OpenID Connect also adds token validation and provides a standardized solution for authentication.