OAuth, SAML, and OpenID Connect: Key Differences and Use Cases

April 2025

Introduction

OAuth 2.0, SAML, and OpenID Connect are protocols designed to ensure secure authentication and authorization in web and mobile applications. While OAuth 2.0 focuses on granting secure access to resources, SAML facilitates Single Sign-On (SSO) in enterprise environments, and OpenID Connect builds on OAuth 2.0 to provide identity authentication alongside authorization.

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Overview of OAuth 2.0, SAML, and OpenID Connect

1. OAuth 2.0:

   • Purpose: Enables apps to securely access user resources without exposing credentials.

   • Focus: Authorization, using tokens to grant limited resource access.

   • Typical Use Case: Social media logins, e.g., "Log in with Google" or "Log in with Facebook."

2. SAML (Security Assertion Markup Language):

   • Purpose: Provides authentication and SSO for users accessing multiple applications.

   • Focus: Centralized authentication with XML-based data exchanges.

   • Typical Use Case: Corporate tools like Salesforce, where employees log in once to access multiple systems.

3. OpenID Connect (OIDC):

   • Purpose: Extends OAuth 2.0 to include user authentication and identity verification.

   • Focus: Combines authentication with authorization using lightweight JSON Web Tokens (JWT).

   • Typical Use Case: Modern apps, such as a gaming platform that verifies user identity through third-party accounts.

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How They Work

OAuth 2.0:

• Flow:

  1. User initiates a request (e.g., logging into Spotify using Google).

  2. App redirects to an Authorization Server for permission.

  3. Upon successful authentication, an access token is issued.

  4. The app uses the token to access resources securely.

• Key Features:

  • Focuses on authorization using tokens (Access/Refresh Tokens).

SAML:

• Flow:

  1. User attempts to log into a Service Provider (SP).

  2. SP redirects the user to an Identity Provider (IdP).

  3. IdP authenticates the user and sends back a SAML Assertion (XML document).

  4. SP validates the assertion and grants access.

• Key Features:

  • Enables SSO across multiple enterprise tools.

OpenID Connect (OIDC):

• Flow:

  1. User logs in via an Identity Provider (e.g., Google).

  2. IdP authenticates the user and issues:

     • ID Token: Verifies the user’s identity.

     • Access Token: For resource authorization.

  3. App uses the tokens to authenticate the user and access resources.

• Key Features:

  • Lightweight and modern, built on OAuth 2.0.

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Comparison Summary

Feature	OAuth 2.0	SAML	OpenID Connect
Purpose	Authorization	Authentication (SSO)	Authentication & Authorization
Focus	Resource access	Single login for enterprise apps	Verify identity and access control
Message Format	JSON, Tokens (JWT)	XML-based	JSON, Tokens (JWT)
Use Cases	Social media logins, API access	Enterprise systems, corporate tools	Modern apps requiring authentication
Real Case Example	Spotify integrating Facebook login	Employees accessing Salesforce via Okta	A gaming platform enabling secure logins with Xbox credentials

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How to Select the Right Protocol

1. Choose OAuth 2.0 if:

   • Your app needs to grant resource access securely without exposing credentials.

   • Focus is on authorization, not authentication.

   • Example: A fitness app accessing user data from Fitbit.

2. Choose SAML if:

   • You are working in an enterprise setting that requires SSO across internal tools.

   • XML-based systems are standard.

   • Example: Employees logging into Salesforce and Slack through a corporate IdP like Okta.

3. Choose OpenID Connect if:

   • Your app requires both authentication and authorization.

   • You’re building modern apps with lightweight JSON support.

   • Example: A gaming platform enabling secure logins with Xbox credentials.

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