OAuth2 & OpenID Connect Deep Dive · Lesson

Authorization Code Flow with OIDC

Implement the secure Authorization Code Flow, now extended with OIDC to return an ID Token alongside the access token.

Authorization Code Flow with OIDC 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.

OIDC & Auth Code Flow Intro

Welcome! In this lesson, we'll combine the secure Authorization Code Flow from OAuth2 with OpenID Connect (OIDC). This allows an application to not only get permission to access resources (OAuth2) but also to verify the user's identity (OIDC).

Think of it as getting both a key to a safe and a valid ID card for the person holding the key, all in one go!

Requesting Identity with OIDC

When using the Authorization Code Flow with OIDC, your application (the Client) starts by sending an authorization request to the Authorization Server. This request is similar to OAuth2 but includes specific OIDC parameters.

response_type=code: Specifies we want an Authorization Code.
scope=openid ...: Crucially, includes the openid scope to signal an OIDC request.
nonce: A unique string to prevent replay attacks (optional but recommended).

The Essential `openid` Scope

The openid scope is the magic flag that tells the Authorization Server you're performing an OpenID Connect request, not just a plain OAuth2 request.

Without openid in your request's scope, the Authorization Server will treat it as a standard OAuth2 flow and will not issue an ID Token.

You can combine openid with other standard OAuth2 scopes like profile, email, or custom scopes.

Beyond `openid`: More Scopes

While openid is mandatory, other OIDC-specific scopes allow you to request more user information:

profile: Access to default profile claims (name, family name, gender, picture, etc.).
email: Access to the user's email address and verification status.
address: Access to the user's postal address.
phone: Access to the user's phone number and verification status.

These claims are then included in the ID Token or accessible via the UserInfo Endpoint.

User Consent & Code Grant

After your app sends the authorization request, the user is redirected to the Authorization Server. They log in (if needed) and are prompted to consent to your app's requested scopes.

If the user approves, the Authorization Server redirects the user back to your app's registered redirect URI, including the Authorization Code in the URL query parameters.

The Token Exchange

Now, your application (running on a server, for confidential clients) takes the received Authorization Code and exchanges it directly with the Authorization Server's token endpoint.

This is a back-channel request, meaning it happens directly between your server and the Authorization Server, not through the user's browser.

Crucially, this exchange now returns three important pieces of information:

Access Token
Refresh Token (if requested)
ID Token

What is the ID Token?

The ID Token is a JSON Web Token (JWT) that contains claims about the authenticated user. It's signed by the Authorization Server, allowing your application to verify its authenticity.

Unlike the Access Token (which is for resource access), the ID Token is specifically for identity verification. It tells your application *who* the user is, not *what* they can do.

ID Token for Identity, Access Token for API

Once your application receives the tokens:

ID Token: You can decode and validate the ID Token to confirm the user's identity and retrieve basic profile information (claims). This is often used for user login sessions.
Access Token: This token is then used to make requests to protected Resource Servers (APIs) on behalf of the user, granting access to specific resources based on the requested scopes.

OIDC Auth Code Flow in Action

Here's a simplified conceptual look at the server-side token exchange. In a real application, you'd use an OIDC client library.

public class OidcClientExample {
  public static void main(String[] args) {
    // 1. User is redirected to Auth Server
    //    Example URL:
    //    https://auth.example.com/oauth/authorize?
    //      response_type=code&
    //      client_id=my_app_id&
    //      scope=openid%20profile%20email&
    //      redirect_uri=https://my-app.com/callback&
    //      nonce=random_string
    
    // 2. User grants consent, redirected back with code
    String authCode = "some_long_authorization_code"; // From redirect URI
    
    // 3. Exchange code for tokens (server-side POST request)
    System.out.println("Exchanging Authorization Code for tokens...");
    // This part would typically be handled by an HTTP client
    // sending a POST request to the token endpoint.
    // The response would contain:
    // {
    //   "access_token": "...",
    //   "token_type": "Bearer",
    //   "expires_in": 3600,
    //   "refresh_token": "...",
    //   "id_token": "..." // The OIDC addition!
    // }
    System.out.println("Received Access Token, Refresh Token, and ID Token!");
    System.out.println("ID Token contains user identity claims.");
  }
}

OIDC Auth Code Flow Check

Consider an application implementing the OpenID Connect Authorization Code Flow.

Which of the following parameters is essential in the initial authorization request to ensure an ID Token is returned?

OIDC Auth Code Flow Recap

Great job! You've learned how the secure Authorization Code Flow is extended by OpenID Connect to provide both authorization and identity.

We use response_type=code and include the openid scope.
The Authorization Server returns an Authorization Code.
This code is exchanged for an Access Token (for resource access) and an ID Token (for user identity).
The ID Token is a JWT carrying user claims, signed by the Authorization Server.

This flow is highly recommended for confidential clients like web applications.

Frequently asked questions

Is the “Authorization Code Flow with OIDC” lesson free?

Yes — the full text of “Authorization Code Flow with OIDC” 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 “Authorization Code Flow with OIDC”?

Implement the secure Authorization Code Flow, now extended with OIDC to return an ID Token alongside the access token. 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 “Authorization Code Flow with OIDC” 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.

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