SAML vs OAuth 2.0: A Practical Guide for Developers

The text explores the distinct roles of SAML 2.0 and OAuth 2.0 in modern B2B SaaS environments, emphasizing that they are complementary rather than competing protocols. While SAML 2.0 is primarily used for authentication in enterprise single sign-on (SSO) scenarios, carrying identity assertions between corporate identity providers and service providers, OAuth 2.0 functions as an authorization framework, enabling applications to access APIs on behalf of users without sharing credentials. OpenID Connect (OIDC) is highlighted as an identity layer on top of OAuth 2.0, enhancing it with user authentication capabilities. The document underscores that most enterprise-scale SaaS applications employ both protocols: SAML for authentication with external identity providers and OAuth (often with OIDC) for API access and internal service authorization. It also discusses the security implications, the importance of token management, and the practical use of broker layers to translate between SAML and OIDC, thereby simplifying integration with existing authentication stacks.