How do I choose between OAuth, SAML, and OIDC for a product login flow?

A practical way to choose is to start with the kind of product and identity integration you need:

Quick rule of thumb

• OIDC (OpenID Connect): best default for modern product login.
• SAML: best when you need to integrate with enterprise SSO / older IdPs.
• OAuth 2.0: best for API authorization, not login by itself.

What each one is for

OAuth 2.0

• Purpose: authorization
• Use it when: your app needs permission to access an API on behalf of a user
• Not ideal for: user authentication/login
• Example: “Allow this app to access your Google Drive files”

OAuth tells you what the app can access, not reliably who the user is.

OIDC

• Purpose: authentication + identity on top of OAuth 2.0
• Use it when: you want “Login with X” or your own SSO flow in a modern app
• Pros: JSON/REST-friendly, easier for web/mobile/SPAs, supports user info and ID tokens
• Example: “Sign in with Google”, “Sign in with Microsoft”, custom enterprise login in a SaaS app

If you’re building a product login flow today, OIDC is usually the best first choice.

SAML

• Purpose: authentication/SSO, especially in enterprise environments
• Use it when: your customers are businesses and their IdP supports SAML
• Pros: widely supported by enterprises, common in older corporate IdP setups
• Cons: XML-heavy, more complex, less convenient for mobile/API-first architectures
• Example: employees logging into a B2B SaaS app via Okta, ADFS, Ping, OneLogin

How to decide

Choose OIDC if:

• You’re building a consumer app or modern SaaS
• You need web/mobile login
• You want easier developer experience
• You want to support social logins or modern enterprise IdPs
• You want a single protocol for authentication across clients

Choose SAML if:

• Your customers are enterprises that already require SAML
• You need to integrate with legacy corporate identity providers
• Sales/IT buyers explicitly ask for SAML SSO
• You’re supporting a lot of existing enterprise identity infrastructure

Choose OAuth if:

• Your main need is API access, not login
• You’re authorizing third-party apps to access user data
• You’re designing delegated permissions/scopes for resource access

Common product patterns

Consumer app

• Use OIDC
• Possibly add social identity providers through OIDC

B2B SaaS

• Use OIDC for default/new integrations
• Also support SAML if enterprise customers need it
• Many SaaS products support both

API platform

• Use OAuth 2.0 for access delegation
• If users also need to sign in, pair it with OIDC

Important note

Many people say “OAuth login,” but strictly speaking:

• OAuth = authorization
• OIDC = login/authentication

If you need to know “who the user is,” prefer OIDC, not OAuth alone.

Simple recommendation

If you’re unsure:

1. Start with OIDC
2. Add SAML only if enterprise customers require it
3. Use OAuth for API permissions, not as your login mechanism

If you want, I can also give you a decision tree or a comparison table for web, mobile, SPA, and enterprise scenarios.