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Choosing between SAML 2.0, OAuth 2.0, and OpenID Connect is one of the most common architectural decisions in modern application development. Get it right and your users have a seamless sign-in experience. Get it wrong and you end up with token theft, weak session handling, and a stack of bolt-on workarounds. This 2026 guide gives you a clear decision tree and explains the trade-offs with real examples.
The fundamental difference
SAML 2.0 is a federated authentication protocol that exchanges XML assertions. OAuth 2.0 is an authorization framework that issues access tokens for delegated access to APIs. OpenID Connect (OIDC) is an identity layer on top of OAuth 2.0 that issues ID tokens (JWTs) for sign-in. The mental model: SAML = "log me in", OAuth = "let my app act on my behalf", OIDC = "log me in and tell my app who I am".
When to use SAML 2.0
Use SAML 2.0 for enterprise SSO with legacy applications and B2B federation where the IdP and SP are in different trust domains. Typical examples: Salesforce, ServiceNow, Workday, Ariba, SAP. SAML is mature, well-supported in enterprise IdPs, and battle-tested for 15+ years.
When to use OAuth 2.0
Use OAuth 2.0 when an application needs to call an API on behalf of a user. The classic example: a mobile app that posts to your Twitter feed. The user authorizes the app, the app gets an access token, and the API accepts the token. OAuth 2.0 is not an authentication protocol — it never tells the app who the user is.
When to use OpenID Connect
Use OpenID Connect for modern sign-in flows: consumer apps (Sign in with Google), single-page apps, native mobile apps, and B2B SaaS where the IdP is in a different trust domain. OIDC gives you a JWT ID token, a UserInfo endpoint, and standardized claims (email, name, picture). It is the de-facto standard for new applications in 2026.
Token formats and security
SAML uses XML assertions (base64-encoded). OAuth 2.0 access tokens are usually opaque or JWT. OIDC ID tokens are always JWTs. For web apps and SPAs, prefer short-lived access tokens with refresh-token rotation. For mobile, use PKCE and certificate pinning. For service-to-service, use mTLS or OAuth client credentials.
Indian enterprise reality
In Indian BFSI and IT services, you will see all three. Salesforce, Workday, and SAP are SAML. Modern fintech and consumer apps are OIDC. Internal APIs are OAuth 2.0 with Azure AD. The SkilBrill IAM Training in Chennai covers all three protocols with hands-on labs in Azure AD, Okta, and Keycloak.
Decision tree
1. Is the use case "log the user into an existing app"? Yes → SAML 2.0 (legacy) or OIDC (modern). 2. Is it "let my app call an API on the user’s behalf"? → OAuth 2.0. 3. Is it both, and the app needs to know who the user is? → OIDC. 4. Is the user a machine (service-to-service)? → OAuth 2.0 client credentials + mTLS.
Common mistakes
Using OAuth 2.0 for sign-in (without OIDC), storing access tokens in localStorage (XSS risk), using implicit flow in 2026 (deprecated), and not validating JWT signatures. Always use the authorization code flow with PKCE for public clients, and validate all tokens server-side.
Talk to a Chennai Counsellor
This is one of the deepest topics in the SkilBrill IAM Training in Chennai, with a dedicated week on protocols and 25 interview questions on this material. Talk to a counsellor to learn more.
Ready to start? Call +91 8610964691, WhatsApp us, or enrol online. Visit us at No 22, 200 Feet Radial Road, Thoraipakkam, Chennai 600097.
