OAuth 2.0: Primarily used for authorization to grant applications access to resources on behalf of users. It’s commonly used in app-to-app communication and access to APIs.
SAML: Primarily used for enterprise SSO, especially in web-based applications. It’s focused on authentication and is widely adopted in enterprise environments for user identity management.
OpenID Connect (OIDC): Extends OAuth 2.0 for authentication, enabling user login and identity verification with an added authorization layer. OIDC is often used for modern web and mobile applications to authenticate users and manage sessions.
The below table highlight the key difference and use cases between the 3 most commonly used modern protocols
| Feature | OAUth2 | SAML | OIDC |
| Use case | API access, app-to-app and app-to-resource access (permissions for specific actions) | Enterprise SSO for web-based applications | Authentication for mobile and web applications, identity verification |
| Purpose | Authorization (delegated access) | Authentication (primarily SSO) | Authentication with an added authorization layer |
| Token type | Access token (Bearer token) | XML-based SAML assertions | ID token (JWT format, includes access tokens) |
| Protocol | HTTP-based with JSON payload | XML-based SOAP over HTTP | HTTP-based with JSON payload (built on OAuth 2.0) |
| Authentication types | Separate from OAuth; OAuth by itself doesn’t perform authentication | Performs both authentication and authorization | Authentication is part of OIDC; extends OAuth 2.0 with user authentication |
| Client types | Web apps, mobile apps, single-page apps, backend services | Primarily web-based enterprise applications | Web apps, mobile apps, single-page apps |
| Supports SSO | Not by itself, can be part of SSO systems when combined with OIDC | Yes, commonly used for SSO in enterprise environments | Yes, supports SSO across applications |
| Limitations | Doesn’t authenticate users directly, complex to implement for authentication | XML-based and can be complex to implement | Dependent on OAuth 2.0, can be complex for specific use cases |
| Use cases | Third-party API access (Google APIs, Facebook APIs) | Enterprise SSO (e.g., Okta, Ping Identity) | User login for mobile and web apps (e.g., “Sign in with Google”) |
