SAML and OpenID Connect both deliver Single Sign-On (SSO), but were built for different architectures. Choose the wrong authentication protocol, and you’ll wrestle with complex XML parsing, certificate rotation challenges, or mobile integration gaps.

SAML 2.0 (OASIS standard, 2005) was designed for enterprise XML-based identity federation. Traditional web apps that connect to enterprise IdPs are typical examples. OpenID Connect (OpenID Foundation, 2014) extends OAuth 2.0 with a lightweight JSON authentication layer optimized for APIs, mobile apps, and modern web architectures. The choice comes down to your target platform and what’s already in your identity stack.

Example: Your company acquired a startup. The startup’s React app needs to support both consumer users authenticating with Google (OIDC) and your enterprise employees authenticating through the corporate identity provider (SAML). An IdP handles both protocols, so your React app maintains a single integration point, rather than implementing separate OIDC and SAML flows.

Aspect	SAML 2.0	OpenID Connect (OIDC)
Primary Focus	Enterprise federation	Modern authentication with OAuth 2.0
Data Format	XML assertions with digital signatures	JSON Web Tokens (JWTs) for ID tokens
Foundation	XML-based authentication and federation protocol	Authentication layer built on OAuth 2.0
Transport	Primarily HTTP-POST and HTTP-Redirect bindings (Browser SSO profile)	HTTPS with front-channel redirects and direct token/UserInfo endpoint calls
Setup	Exchange XML metadata, manage certificates	Client registration via discovery documents (.well-known/openid-configuration)
Token Format	Signed (and optionally encrypted) XML	JWTs for ID tokens; access tokens are implementation-specific (While OAuth 2.0/OIDC doesn’t mandate JWT access tokens, they’re increasingly common)
Best For	Environments with legacy government or regulated-industry federation requirements	SPAs, mobile apps, microservices, social login
Integration Complexity	Higher: XML parsing, metadata management, certificate rotation	Generally lower: JSON parsing, simple HTTP calls, discoverable configuration

Key differences that matter: SAML assertions can carry rich attribute hierarchies for complex enterprise requirements. OIDC uses scopes (openid, profile, email) to request specific claims in the ID token and, optionally, via the UserInfo endpoint.

SAML runs independently of OAuth 2.0. OIDC layers authentication on top of OAuth 2.0 authorization flows, enabling a unified protocol stack for both authentication and authorization.

SAML (SP-Initiated Flow): Your Service Provider (SP) redirects users to the IdP with an AuthnRequest. The IdP authenticates them, generates a signed assertion containing user attributes, and returns it to the SP’s Assertion Consumer Service (ACS) via HTTP-POST. You validate the signature and assertion conditions, then grant access. This flow typically involves multiple browser redirects and XML processing overhead.

OIDC (Authorization Code Flow with PKCE): Your app redirects users to the IdP’s authorization endpoint with required scopes and a PKCE code challenge. After authentication and consent, the IdP returns an authorization code. You exchange this code (along with the PKCE verifier) for an ID token and an access token, and may receive a refresh token, depending on the client type and the IdP policy. Validate the JWT signature, check claims (iss, aud, exp), and you’re done. This flow is typically simpler to implement due to native JSON/JWT support in modern platforms.

Match your architecture to the proper protocol:

Choose SAML when:

• Integrating with existing enterprise IdPs
• Building for government or regulated industries requiring FISMA, FedRAMP, or legacy SAML-based federation
• Working with systems that already speak SAML, where switching costs exceed benefits
• Handling complex user attribute requirements (nested organizational hierarchies, custom claims)

Choose OIDC when:

• Building single-page applications (React, Vue, Angular) or mobile apps (iOS, Android)
• Adding social login providers (Google, GitHub, Apple)
• Creating API-first architectures or microservices that need OAuth 2.0 access tokens
• Starting fresh with no legacy constraints, where OIDC’s more straightforward setup reduces time to production
• Prioritizing developer experience with better libraries and documentation

What if you need both? IdPs can handle protocol mediation. The application speaks OIDC while connecting to SAML-based enterprise IdPs. You avoid having to manage two protocol implementations.

Token Validation

• For OIDC: Verify JWT signatures using the IdP’s published JSON Web Key Set (JWKS), check expiration (exp), validate audience (aud) matches your client ID, and confirm issuer (iss) matches your IdP.
• For SAML: Verify XML signatures, check expiration conditions (NotBefore, NotOnOrAfter), and validate Audience restrictions.

Client Configuration

Never embed client secrets in SPAs or mobile apps; they’re visible in browser dev tools and app binaries. Use Proof Key for Code Exchange (PKCE) for authorization code flow. PKCE protects against authorization code interception without requiring a secret, which is mandatory for public clients (RFC 7636).

Session Management

OIDC inherits refresh token support from OAuth 2.0 for long-lived sessions. Exchange the refresh token for new access tokens when they expire, assuming your IdP issues refresh tokens, and the client configuration allows it. SAML relies on IdP- and SP-managed sessions rather than a standardized refresh mechanism, and supports optional Single Logout (SLO), whose implementation differs across IdPs and can be challenging to standardize.

Error Handling

Log authentication failures with context (timestamps, error codes, client IDs, IdP responses) for debugging. Show users generic “authentication failed” messages. Avoid exposing token details, claim mismatches, or signature failures that could aid attackers.

Is OpenID Connect replacing SAML?

No, they’re coexisting. OIDC adoption is growing rapidly for consumer-facing apps and mobile development due to its foundation in OAuth 2.0. However, SAML remains the standard in the enterprise and government sectors due to infrastructure investments and compliance requirements (FISMA, FedRAMP). Most organizations run both protocols: OIDC for new applications, SAML for enterprise federation.

Which protocol is more secure?

Both provide strong security when properly implemented. SAML uses XML signatures and optional encryption; OIDC uses JWT signatures and HTTPS. The key difference: OIDC’s PKCE extension (RFC 7636) secures public clients, such as mobile apps and SPAs, where client secrets cannot be protected. SAML can achieve similar protections using artifact binding or holder-of-key assertions, but these patterns are less common in modern application development. Security depends on the implementation, not which protocol you choose.

Why do mobile apps prefer OIDC over SAML?

OIDC’s Authorization Code Flow with PKCE was designed for public clients, like mobile apps, that cannot securely store client secrets. OIDC's JSON tokens integrate natively with mobile SDKs, while SAML requires XML processing libraries. OIDC supports custom URI schemes (iOS) and App Links (Android) for seamless authentication. Major providers primarily support OIDC-based flows for mobile authentication.

What’s the best migration path from SAML to OIDC?

Migrate incrementally. Implement OIDC for new applications while maintaining existing SAML integrations. Use an identity platform that supports protocol mediation so your applications speak OIDC while connecting to SAML-based enterprise IdPs. This minimizes risk without disrupting existing federation relationships. Many enterprises maintain hybrid environments during transitional phases. Use an identity platform that handles protocol mediation, allowing applications to use OIDC while the platform manages SAML federation.

What is the difference between OAuth 2.0 and OIDC?

OAuth 2.0 handles authorization (access to APIs) through access tokens. OIDC adds authentication (user identity verification) through ID tokens built on OAuth 2.0. When you implement “Sign in with Google,” you’re using OIDC for authentication plus OAuth 2.0 for API access. OIDC extends OAuth 2.0 with standardized identity claims and the UserInfo endpoint.

Choosing between SAML and OIDC is essential for securing your authentication architecture. Both protocols require careful implementation, including proper token validation, certificate management, and session handling. Implementing and maintaining both protocols is a complex process.

Auth0 supports both SAML and OIDC, handling protocol mediation and security best practices so developers can focus on application features.

Explore our Intro to IAM series for additional topics related to identity and access management.

Learn more

These materials are intended for general informational purposes only. You are responsible for obtaining security, privacy, compliance, or business advice from your own professional advisors and should not rely solely on the information provided herein.