SSO vs OAuth: Key Differences You Must Know

OAuth is not SSO, though developers often mix the two up.

Most of the confusion stems from the fact that OAuth providers like Google allow users to use their accounts to log in to multiple apps — something SSO also does.

These providers use OAuth as part of the authentication process, so when developers see the OAuth flow during the authentication process, they assume the entire process is using OAuth.

In this article, we’ll clarify the differences between OAuth and SSO and help you determine which one you should use.

OAuth vs SSO: What are they + which is right for you?

OAuth (Open Authorization) 2.0 is an authorization protocol that allows users to grant one app limited access to their data on another app or service.

SSO (Single Sign-On) is an authentication method that allows users to authenticate once with an Identity Provider (IdP) and gain access to multiple apps.

With OAuth you don’t give the user access, rather the user gives you permission to access another app on their behalf. With SSO, you give the user access to your app.

Use OAuth if: You're building an app that needs to access or modify users’ data on another app. For example, a social media management tool that needs to post Facebook or X updates on behalf of a user.

Use SSO if: You want to enable corporate login to your app with your customer’s enterprise IdP like Okta or Microsoft Entra.

Remember, the choice of whether to use OAuth or SSO hinges on whether your priority is gaining access to a user’s data (OAuth) or simplifying the login process (SSO).

What is OAuth?

OAuth is an authorization protocol that lets users grant apps access to their information without handing over their credentials. It was built to allow one app to access another app on behalf of a user.

Instead of the user’s identifying information, your app receives an access token that it can then exchange for the user’s info.

What can you use OAuth for?

You can use OAuth for:

• Apps that need access to user data, stored in other apps — for example, accessing a user’s Facebook friends or Google Drive files.
• Social logins (when combined with OIDC) to let users use their social accounts like Google or Facebook to log in to your app.
• Platforms where other developers need to interact with your APIs or services. You can use OAuth to allow these developers to ask for permission to access the services you offer.
• Device authorization to authorize users in devices with limited input capabilities such as smart TVs and gaming consoles.

When should you use OAuth?

You should use OAuth when you want to access or modify data in another service on behalf of a user. For example, use OAuth when you want to access a user’s GitHub repos without asking them for their username and password.

Just keep in mind users control the level of access they give you and can revoke your app’s permissions if they need to.

When is OAuth not a good fit?

OAuth is not a good fit if you need to verify the user’s identity — it’s best suited for user-level authorization between apps. If you need to authenticate users, check out the OpenID Connect (OIDC) protocol, which adds authentication to OAuth.

What is SSO?

Single Sign-On (SSO) is an authentication method that allows users to authenticate once and gain access to multiple apps.

A good example of SSO in action is when you use an Atlassian account to sign in to Jira, Confluence, and Bamboo — a suite of apps from one provider — or more commonly, when enterprise employees use their Okta logins to log in to all the SaaS apps used within their company.

What protocols support SSO?

Security Assertion Markup Language (SAML) and OIDC are two of the most common SSO protocols. SAML is an older XML-based protocol that’s been around for decades. It’s known for its complexity which makes it more challenging to implement securely. Support it if you want to enable legacy enterprise logins or if your customers specifically ask for it. Just make sure it’s set up correctly and you thoroughly validate responses from IdPs — any misconfigurations can create potential security vulnerabilities.

For an easier to secure setup use OIDC, an authentication protocol built on top of OAuth. It’s far easier to implement and compatible with a wider range of apps compared to SAML. Plus, most enterprise IdPs now support it.

What can you use SSO for?

You can use SSO for:

• Enterprise logins: SSO is one of the first features your enterprise clients will ask for because they prefer to manage user access to the hundreds of apps they use through a central IdP. If you want to land these clients, support SSO and integrate with your customer’s IdP.
• Authenticating users to an ecosystem of apps: If you're developing multiple applications that form an ecosystem (for example, a suite of tools for productivity, collaboration, or education), you want to offer users a unified experience. This includes making sure they can move between different apps without having to log in separately for each one.

When should you use SSO?

You should use SSO when you want to authenticate users via a centralized identity provider. Users can log into an IdP and gain access to all the apps and services connected to that IdP without repeatedly authenticating with each.

When is SSO not a good fit?

SSO is not a good fit for small-scale consumer apps where users don’t need to switch between multiple platforms — it’s overkill. For most of these apps, a social and a traditional email/password login combo is usually enough.

Should you use OIDC or SAML for SSO?

Most modern identity providers support both OIDC and SAML. You’ll probably want to use OIDC though — it’s way easier to implement and more secure than SAML.

SAML is based on XML, a markup language that’s complex to parse and process. This complexity increases the attack surface for XML-based attacks, such as XML Signature Wrapping (XSW) and XML External Entity (XXE) Injection, making SAML implementations more susceptible to certain types of vulnerabilities like message interceptions and denial of service.

OIDC, on the other hand, uses JSON/REST for communication, which is easier to understand. It also uses tokens which are simpler to process compared to SAML assertions.

In some cases, especially if your app targets a diverse range of clients (including both modern startups and established enterprises), it may be beneficial to support both OIDC and SAML.

Adding SSO to your app

Before you dive headfirst into building your own SSO solution, you should know each identity provider does SSO a bit differently. Given that your customers likely use a variety of IdPs, you could end up building custom integrations for each new client you bring on board. That’s a lot of work for your engineering team.

Instead of dealing with all these complexities, why not use WorkOS? It lets you add SSO for all major IdPs to your app with just a few lines of code.

• Get started fast: With SDKs in every popular language, and Slack-based support, you can implement SSO in minutes rather than weeks.
• Support every protocol: With OAuth 2.0 integrations to popular providers like Google and Microsoft, compatibility with every major IdP, and full support for custom SAML/OIDC connections, WorkOS can support any enterprise customer out of the box.
• Avoid the back-and-forth: WorkOS’s Admin Portal takes the pain out of onboarding your customers’ IT teams and configuring your app to work with their identity provider.
• Pricing that makes sense: Unlike competitors who price by monthly active users, WorkOS charges a flat rate for each company you onboard — whether they bring 10 or 10,000 SSO users to your app.

Explore Unified SSO by WorkOS.