OAuth 2.0 vs SAML

Overview

OAuth 2.0 and SAML are both standards used to secure access, but they were designed for different jobs. SAML (Security Assertion Markup Language) is an XML-based standard for authentication and single sign-on, especially across enterprise web applications. OAuth 2.0 is a framework for authorization—granting an application delegated access to resources—commonly paired with OpenID Connect (OIDC) to add an authentication layer.

Key Differences

The central distinction is authentication versus authorization. SAML answers 'who is this user?' and asserts that identity to a service provider. OAuth answers 'what is this app allowed to do on the user's behalf?' by issuing access tokens scoped to resources. Pure OAuth does not standardize authentication; OIDC builds that on top of OAuth, which is why modern login flows usually mean OIDC rather than raw OAuth.

Format and ergonomics differ sharply. SAML exchanges large XML assertions, often via browser POST bindings, which is robust but heavy. OAuth and OIDC use compact JSON tokens (frequently JWTs) and simple HTTP redirects, which work much better on mobile apps, single-page apps, and API clients.

Adoption reflects their eras. SAML is deeply entrenched in enterprises, with strong support in corporate identity providers and legacy SSO integrations. OAuth/OIDC dominate new development and consumer-facing 'sign in with' experiences.

When to Choose OAuth 2.0

Choose OAuth 2.0 (with OIDC for login) for new applications, mobile and single-page apps, and API authorization. Its compact tokens, redirect-based flows, and broad library support make it the natural fit for modern, distributed, API-driven systems.

When to Choose SAML

Choose SAML when integrating with enterprise single sign-on and partner federations that already standardize on it. Many corporate identity providers and B2B relationships expect SAML, and it provides authentication natively without an extra layer.

Verdict

OAuth 2.0 (typically via OIDC) is the default for new apps and API access, while SAML remains the backbone of established enterprise SSO and B2B federation. They are not mutually exclusive: identity providers commonly support both, letting organizations use SAML for legacy enterprise apps and OAuth/OIDC for modern services. Choose by use case and the ecosystem you must integrate with.