What is the difference between OAuth and OpenID Connect?

Question

ICSM Computer · Answer

The difference between OAuth 2.0 and OpenID Connect (OIDC) lies in
purpose:
Protocol
Purpose
Use Case
OAuth 2.0
Authorization (access control)
"Can this app access my data?"
OpenID Connect
Authentication (user identity)
"Who is this user?"
OAuth 2.0: Authorization Framework
Goal: Allow a third-party app to access a resource on behalf of a user.Does NOT identify who the user is.Returns: Access Token (for accessing APIs).Use Case: Grant app access to your Google Drive files 
without sharing password.
Example:
A fitness app wants access to your Fitbit data (but doesn't need your email or who you are).
OpenID Connect (OIDC): Identity Layer on Top of OAuth 2.0
Built on top of OAuth 2.0.Adds authentication capabilities.Returns: ID Token (JWT format), plus access token.Use Case: Let users log in to your app with Google, Microsoft, etc.
Example:
Your app lets users log in with their Google account → you get who the user is (email, name, etc.).
Technical Differences
Feature
OAuth 2.0
OpenID Connect
Primary Purpose
Authorization
Authentication + Authorization
Token Types
Access Token
Access Token + ID Token (JWT)
User Info
Not provided
Provided via userinfo endpoint
Standard Login Flow
Not defined
Well-defined login process
Token Validation
App-defined
JWT signature validation supported
Scopes
e.g., read, write
Includes openid, profile, email
Example: Login with Google
If you just use OAuth 2.0, you'll get an access token for calling APIs (e.g., Google Calendar API), but
you won't know who the user is.
If you use OpenID Connect, you'll also get:
id_token: contains user identity info (email, sub, name, etc.)Access to a userinfo endpoint for more user claims
Summary
Use OAuth 2.0 if you only need to authorize access to APIs.Use OpenID Connect if you want to log in users and get their identity.

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What is the difference between OAuth and OpenID Connect?

ICSM Computer

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1 Answers

OAuth 2.0: Authorization Framework

Example:

OpenID Connect (OIDC): Identity Layer on Top of OAuth 2.0

Example:

Technical Differences

Example: Login with Google

Summary

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Protocol	Purpose	Use Case
OAuth 2.0	Authorization (access control)	"Can this app access my data?"
OpenID Connect	Authentication (user identity)	"Who is this user?"

Feature	OAuth 2.0	OpenID Connect
Primary Purpose	Authorization	Authentication + Authorization
Token Types	Access Token	Access Token + ID Token (JWT)
User Info	Not provided	Provided via `userinfo` endpoint
Standard Login Flow	Not defined	Well-defined login process
Token Validation	App-defined	JWT signature validation supported
Scopes	e.g., `read`, `write`	Includes `openid`, `profile`, `email`