OIDC: Identity Layer on OAuth2
Discover how OpenID Connect adds an identity layer atop OAuth2, enabling authentication and identity federation.
OIDC: Identity Layer on OAuth2 is a free OAuth2 & OpenID Connect Deep Dive lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the OAuth2 & OpenID Connect Deep Dive learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Welcome to OpenID Connect!
You've learned about OAuth2 for authorization. Now, let's explore OpenID Connect (OIDC), the identity layer built on top of OAuth2.
OIDC helps applications verify a user's identity and get basic profile information securely.
OAuth2: Delegation, Not Identity
Remember, OAuth2 is an authorization protocol. It's designed to grant limited access to a user's resources without sharing their credentials.
- It tells you what a client can do.
- It doesn't tell you who the user is.
The Identity Gap
Imagine a user logging into an app using their Google account. OAuth2 would let the app access their Google Drive, but it wouldn't inherently tell the app the user's name or email.
Applications often need to know who the user is to personalize experiences or manage accounts.
OIDC Bridges the Identity Gap
This is where OpenID Connect comes in! OIDC is a simple identity layer built on top of the OAuth2 protocol.
It provides a standardized way for clients to verify the identity of an end-user based on the authentication performed by an Authorization Server.
OIDC's Primary Goal: Authentication
At its heart, OIDC is about authentication. It answers the question: "Who is this user?"
- Confirms the user's identity.
- Ensures the user is who they claim to be.
- Done by an Identity Provider (IdP).
User Identity through Claims
In OIDC, user identity is communicated through a special type of security token called an ID Token.
The ID Token contains pieces of information about the user, known as claims. These claims include things like the user's name, email, or a unique identifier.
The ID Token: Identity Proof
The ID Token is a JSON Web Token (JWT). It's signed by the Identity Provider, allowing client applications to verify its authenticity.
It's the core component that carries the user's identity information from the Identity Provider to the client.
Enabling Identity Federation
OIDC also enables identity federation. This means a user can use one set of credentials (e.g., their Google account) to log into multiple unrelated applications.
The Identity Provider acts as a trusted third party, federating the user's identity across different services.
Why Use OpenID Connect?
OIDC brings several advantages:
- Single Sign-On (SSO): Users log in once and access multiple apps.
- Simplified Development: Standardized identity layer reduces complexity for developers.
- Enhanced Security: Builds on OAuth2's security features.
OIDC vs. OAuth2 Quiz
Let's test your understanding of the core difference between OAuth2 and OpenID Connect.
OIDC: Your Identity Guide
Great job! You now understand that OpenID Connect is an identity layer built on top of OAuth2.
- OAuth2: Authorization (what you can do).
- OIDC: Authentication (who you are), using ID Tokens and claims.
Next, we'll dive deeper into the structure and content of these powerful ID Tokens!
Frequently asked questions
Is the “OIDC: Identity Layer on OAuth2” lesson free?
Yes — the full text of “OIDC: Identity Layer on OAuth2” is free to read here on the web, and the OAuth2 & OpenID Connect Deep Dive course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the OAuth2 & OpenID Connect Deep Dive course, upgrade to CoddyKit PRO.
What will I learn in “OIDC: Identity Layer on OAuth2”?
Discover how OpenID Connect adds an identity layer atop OAuth2, enabling authentication and identity federation. You practise OAuth2 & OpenID Connect Deep Dive with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start OAuth2 & OpenID Connect Deep Dive?
No prior experience is required. OAuth2 & OpenID Connect Deep Dive on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “OIDC: Identity Layer on OAuth2” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this OAuth2 & OpenID Connect Deep Dive lesson?
Yes. Every OAuth2 & OpenID Connect Deep Dive lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- OIDC: Identity Layer on OAuth2
- ID Tokens & Claims
- OIDC Flows Overview
- The UserInfo Endpoint