If you are building a new login, use OpenID Connect. If enterprise customers ask for SSO, expect to support SAML as well, because it is common in enterprise and intranet sign-in. OWASP recommends OIDC for login and SSO, and describes SAML 2.0 as XML-based and common in enterprise.
What each one is
OIDC adds authentication on top of OAuth 2.0, which on its own is for delegated authorization. The result is an ID token the app validates.
SAML 2.0 is an older XML-based standard. It can be started by either the service provider or the identity provider.
Decision guide
- New consumer or developer-facing app: OIDC.
- Selling to large enterprises with older identity systems: SAML, plus OIDC.
- Modern workforce identity provider and API-first design: OIDC.
- Customer insists on a SAML-only integration: SAML.
- Mobile and single-page apps: OIDC with the authorization code flow and PKCE.
What you must validate in each
For OIDC, OWASP says to check the issuer, audience, signature using the provider's keys, and expiry, using a maintained library and discovery endpoints. Do not implement obsolete OpenID 2.0.
For SAML, run the checks in our SAML validation checklist: signature, destination, audience, InResponseTo, replay and time.
Identify federated users carefully
OWASP says to identify federated users by the combination of issuer and subject, not by email or other profile attributes. Require an authenticated session before linking or unlinking identities, and notify the user. Our existing note on account linking shows why.
Things SSO does not solve
OWASP's secrets guidance warns against assuming OIDC alone prevents phishing or weak passwords at the identity provider. Strong MFA at the IdP still matters. See which MFA to require.
Plan deprovisioning too. SSO removes the login, but accounts and tokens inside the app may remain unless you also remove users automatically. See identity and secrets offboarding.
When you add a second protocol, share as much as you can behind it: one user model, one account linking rule, one session policy and one audit log. Two separate login paths with different rules is how gaps appear, for example MFA enforced on one path and not the other. Write the common rules down once, and test both protocols against them.
Quick check
Can I support only OIDC?
You can, but some enterprise buyers will ask for SAML. Decide based on who you sell to.
Is OAuth the same as OIDC?
No. OAuth handles delegated authorization. OIDC adds authentication on top of it.
Sources
Last reviewed: 19 October 2026.
