OAuth 2.0, OIDC and SAML: differences, use cases and when to use them

OAuth 2.0, OpenID Connect (OIDC) and SAML are the three standards behind modern authentication and authorization. They sound alike but solve different problems: knowing which one to use prevents fragile integrations and lock-in choices that are hard to reverse.

The three protocols in one sentence

• OAuth 2.0 is an authorization framework: it delegates access to a resource without sharing credentials.
• OpenID Connect (OIDC) is an authentication layer built on top of OAuth 2.0: it tells you who the user is.
• SAML is an XML-based authentication and Single Sign-On standard, widespread in the enterprise.

OAuth 2.0: authorization, not authentication

OAuth 2.0 answers the question "can this application access this resource on behalf of the user?". It does not verify identity: it issues an access token that represents a scoped, time-limited permission. It is the protocol that lets an app read your calendar or call an API on your behalf without ever seeing your password.

The classic mistake is using OAuth 2.0 "on its own" for login: the token says what the app can do, not who you are. Authentication needs an extra layer — and that is exactly what OIDC adds.

OpenID Connect: identity on top of OAuth

OIDC extends OAuth 2.0 by introducing the ID token, a signed JWT that carries information about the user (the claims: identifier, email, name). With OIDC the application gets both authentication (who you are) and authorization (what you can do) in a single flow, reusing the entire OAuth 2.0 infrastructure.

It is the de facto standard for modern web and mobile apps and for Single Sign-On toward providers like Google Workspace and Microsoft Entra ID. Lightweight, JSON- and REST-based, it is almost always the right choice for new integrations.

SAML: the XML-based enterprise standard

SAML (Security Assertion Markup Language) predates OIDC and still dominates many enterprise and B2B contexts. It exchanges signed XML assertions between an Identity Provider (IdP) and a Service Provider (SP) to achieve authentication and SSO. It is mature, robust and supported by practically every legacy enterprise system, but more verbose and less suited to mobile and single-page applications than OIDC.

Comparison table

When to use which

Use OAuth 2.0 when

You need to delegate access to an API or a resource without handling a full login: machine-to-machine integrations, access to third-party services, microservice authorization.

Use OIDC when

You are building a new web or mobile application and need both login and API access. It is the default choice for modern login and for SSO with the major cloud providers.

Use SAML when

You must integrate with existing enterprise systems or B2B customers that mandate SAML as a federation standard. OIDC toward new apps and SAML toward legacy systems often coexist.

Integrating with LoginMaster

LoginMaster supports open standards to avoid lock-in and simplify adoption. You can integrate authentication and SSO through the TypeScript and .NET SDKs or directly via REST API, keeping the Tenant-Cloud architecture in which personal data never leaves the customer's tenant.

• SSO with Google Workspace and Microsoft Entra ID based on OIDC.
• Application integration via TypeScript and .NET SDKs or REST API.
• Dual-signature authentication and configurable 2FA/TOTP on top of the login flow.
• Access events exportable to SIEM (Splunk, QRadar, Sentinel, Elastic).

For the fundamentals, see what IAM is and the security page. To evaluate a concrete integration, request a demo.