As organisations adopt cloud services and modern authentication strategies, many encounter the term OAuth alongside Single Sign-On (SSO). While these technologies are often used together, they are not the same thing.
So, is OAuth Single Sign-On? Not exactly. OAuth is not a Single Sign-On solution in itself, but it enables Single Sign-On when implemented correctly. In this article, we’ll explore what OAuth is, how it differs from SSO, and how they can be combined to improve access security and user experience.
What Is OAuth?
OAuth (Open Authorisation) is an authorisation framework, not an authentication protocol. It allows one service (such as a web or mobile app) to access resources on another service on behalf of a user, without the user needing to share their password.
A familiar example of OAuth in action is the “Sign in with Google” or “Log in with Microsoft” button. The user is redirected to the identity provider (Google or Microsoft), authorises the application to access specific information, and is then redirected back to the original app with an access token.
This process ensures that the user’s credentials are never shared with the third-party app, only the token is passed, which is limited in scope and duration.
What Is Single Sign-On (SSO)?
Single Sign-On (SSO) is an authentication method that enables users to log in once and gain access to multiple systems or applications without needing to log in again during the same session.
SSO is all about streamlining the login experience while maintaining security. It relies on authentication protocols like SAML, OpenID Connect (OIDC), or Kerberos, and OAuth often plays a supporting role when SSO is built using OpenID Connect.
How OAuth and SSO Work Together
While OAuth itself doesn’t authenticate users (that’s not its purpose), it can enable SSO when paired with OpenID Connect (OIDC), which is built on top of OAuth 2.0.
Here’s how they work together:
- User requests access to an application.
- The app redirects the user to an Identity Provider (IdP) using OIDC (which extends OAuth).
- The IdP authenticates the user (often using corporate credentials or MFA).
- The IdP issues an ID token (for authentication) and an access token (for authorisation).
- The user is now logged in and that login session can persist across multiple applications, enabling SSO.
So, while OAuth on its own is about granting permissions, the addition of OpenID Connect brings authentication and SSO capabilities into play.
|
Feature
|
OAuth
|
Single Sign-On (SSO)
|
|
What it is
|
An authorisation framework
|
An authentication method
|
|
Purpose
|
Grants third-party apps access to user resources
|
Enables one login for multiple systems
|
|
Handles authentication?
|
No – unless extended via OpenID Connect
|
Yes
|
|
Token-based?
|
Yes – issues access tokens
|
Yes – uses session or identity tokens
|
|
Common use cases
|
API access, delegated permissions
|
Enterprise user access management
|
Common Use Cases: OAuth-Enabled SSO
In modern SSO deployments, especially those using OpenID Connect, OAuth is used under the hood to:
- Authorise access to cloud applications and APIs
- Enable federated identity and third-party logins (e.g. Google Workspace, Microsoft Entra ID)
- Support secure mobile and web authentication flows
- Integrate with enterprise Identity Providers (IdPs) like Azure AD, Okta, or My1Login
This approach allows organisations to centralise authentication, enhance security controls, and deliver frictionless login experiences for users across platforms.
OAuth is not Single Sign-On, but it underpins many modern SSO solutions, particularly when extended with OpenID Connect. OAuth handles secure authorisation, while SSO focuses on authentication and user session management. When combined, they provide a robust framework for secure, seamless access across applications.
Platforms like My1Login leverage these technologies to deliver enterprise-grade identity and access management, without compromising on user experience or security.
