SAML vs OAuth: What Is the Difference for IT Teams?

Short answer: SAML vs OAuth is authentication versus authorization. SAML (Security Assertion Markup Language) lets an identity provider tell an application who a user is, which is how most enterprise single sign-on works. OAuth 2.0 lets a user or service grant an application limited access to an API without sharing a password. OAuth does not, by itself, sign anyone in.

SAML vs OAuth at a glance

How SAML and OAuth differ

Authentication vs authorization

SAML answers "who is this user?" The OASIS overview describes authentication statements that record how and when a user was authenticated, plus attribute statements such as email or department (OASIS). OAuth answers "what may this app do on the user's behalf?" RFC 6749 describes a third-party application obtaining "limited access to an HTTP service" (RFC 6749).

What the SAML assertion and the OAuth token carry

A SAML assertion is a statement about a person; an OAuth access token is a permission for a client. The SAML assertion is XML, signed by the identity provider, and read by the application. An OAuth access token is meant for the API (resource server), and RFC 6749 does not fix its format, so the client often cannot and should not interpret it.

Who the parties are

SAML has two main roles: the identity provider (IdP), such as Okta or Microsoft Entra ID, and the service provider (SP), the app. OAuth has four: the resource owner (usually the user), the client app, the authorization server that issues tokens, and the resource server that hosts the API.

Where each runs

SAML was built around the browser, moving messages through redirects and form posts. OAuth works for browser apps, but also for mobile apps, command-line tools and server-to-server calls, where posting XML through a browser is not an option.

Why OAuth alone is not a login

OAuth 2.0 is often mistaken for a sign-in protocol because "Sign in with..." buttons use it. The oauth.net authentication article states directly that "OAuth 2.0 is not an authentication protocol" and lists the risks of treating it as one:

• Token is not presence: holding an access token does not prove the user is there, since refresh tokens can mint new ones without the user.
• No audience check: a plain access token does not tell an app whether it was issued for that app, which enables token injection.
• Unverified profile data: user details fetched with the token can be altered if not verified.
• Per-provider code: every provider implements identity details differently.

The standard fix is OpenID Connect, which adds a signed ID token on top of OAuth 2.0. How OpenID Connect compares with SAML is a separate question from SAML vs OAuth.

When to use SAML

SAML fits workforce SSO into web applications, especially established SaaS and enterprise apps.

• Browser-based business apps that list "SAML 2.0" in their SSO settings.
• Centralized sign-in policy: MFA and conditional access run once at the IdP, and the app trusts the assertion.
• Attribute-driven access: the assertion can pass group or department attributes the app maps to roles.
• Older enterprise apps that predate OpenID Connect.

When to use OAuth

OAuth fits whenever an application, not a person at a browser, needs to call an API.

• Integrations: a ticketing tool reading a calendar or a backup tool reading a mailbox, with only the scopes it needs.
• Scripts and services: automation calling an API with a token instead of a stored admin password.
• Mobile and desktop apps calling back-end APIs.
• Revocable, scoped access: removing an app's grant cuts its access without a password reset.

Using SAML and OAuth together

Many environments run both: SAML for signing users in to apps, OAuth for the APIs those apps call. RFC 7522 defines the bridge, a grant type (urn:ietf:params:oauth:grant-type:saml2-bearer) that lets a client present a SAML 2.0 assertion and receive an OAuth access token, without a second user approval step.

Admin tip: when onboarding an app, ask two questions separately: which protocol it supports for user sign-in, and how its integrations authenticate to APIs. A "SAML SSO" checkbox says nothing about how the app's API tokens are issued or revoked.

Bottom line

If you are connecting staff to web apps through an identity provider, SAML is the protocol to look for when an app does not offer OpenID Connect. If an app, script or integration needs to call an API, that is OAuth, and its tokens need their own review of scopes and revocation. To compare platforms that handle both, start with the single sign-on software category or build a list with the software shortlist tool.