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OAuth2 & OpenID Connect Deep Dive · Lesson

Single Sign-On Across Applications

Learn how OAuth2 and OpenID Connect enable Single Sign-On so users authenticate once and access multiple applications seamlessly.

Single Sign-On Across Applications is a free OAuth2 & OpenID Connect Deep Dive lesson on CoddyKit — lesson 4 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.

What Is SSO?

Single Sign-On lets a user authenticate once with a central identity provider and then access many applications without logging in again. OpenID Connect is the modern foundation for web and mobile SSO.

The Central Session

The magic lives at the OpenID Provider (OP). When the user logs in, the OP establishes its own session (often a cookie). Each app relies on that central session rather than maintaining its own credentials.

First App Login

App A redirects the user to the OP's /authorize endpoint. The user enters credentials, the OP sets its session cookie, and returns an authorization code to App A, which exchanges it for tokens.

Second App: Silent Login

Later the user opens App B, which also redirects to /authorize. Because the OP session cookie already exists, the OP recognizes the user and returns a code without prompting for credentials again. That is the SSO experience.

prompt=none

To check silently whether a session exists, apps can use prompt=none. The OP either returns a code immediately or an error like login_required if no session is present.

GET /authorize?response_type=code
  &client_id=appB&scope=openid
  &redirect_uri=https://b.example.com/cb
  &prompt=none

Forcing Re-authentication

Conversely, sensitive operations can require a fresh login with prompt=login or a max_age constraint, overriding the SSO session for that request.

Identity Provider Federation

The OP itself may federate to upstream providers (corporate IdP, Google, social logins). To the apps it still looks like one OP, but the OP brokers authentication to the chosen source. This centralizes policy and simplifies clients.

Single Logout

SSO needs Single Logout too: when the user signs out of one app, related sessions should end. OIDC offers front-channel and back-channel logout to notify participating apps and clear the central session.

Session Token Lifetimes

Balance convenience and security: short access tokens with refresh tokens for ongoing access, and an OP session lifetime that matches your risk tolerance. Long SSO sessions are convenient but widen the impact of a compromised device.

Native and Mobile SSO

On mobile, SSO uses the system browser (ASWebAuthenticationSession / Custom Tabs) so the OP cookie is shared across apps. Embedded WebViews break SSO and are discouraged for security and usability reasons.

Benefits and Risks

SSO improves UX, centralizes MFA and auditing, and reduces password fatigue. The trade-off: the OP becomes a high-value target, so it must be hardened, monitored, and protected with strong authentication.

Quick Check

Test your SSO understanding.

Recap

Single Sign-On centralizes authentication at the OpenID Provider.

  • The OP session lets subsequent apps log in silently.
  • prompt=none checks for a session; prompt=login/max_age force re-auth.
  • Single Logout coordinates ending sessions across apps.
  • Use the system browser, not embedded WebViews, for mobile SSO.

Frequently asked questions

Is the “Single Sign-On Across Applications” lesson free?

Yes — the full text of “Single Sign-On Across Applications” 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 “Single Sign-On Across Applications”?

Learn how OAuth2 and OpenID Connect enable Single Sign-On so users authenticate once and access multiple applications seamlessly. 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 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Single Sign-On Across Applications” 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

  1. Integrating with Identity Providers
  2. Microservices & API Gateway Security
  3. Multi-Factor Authentication (MFA)
  4. Single Sign-On Across Applications
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