What SSO solution should I use for a SaaS app?

For a SaaS app, the best SSO solution is usually an OIDC-first IdP integration layer rather than building your own auth. In practice, the right choice depends on your customers and your stage.

Short answer

If you want the safest default for a SaaS product:

• Use OpenID Connect (OIDC) + SAML support
• Add an abstraction layer for enterprise IdPs
• If you want to buy instead of build, consider:
  • WorkOS if you want the fastest enterprise SSO onboarding
  • Auth0 if you want a broad auth platform
  • Okta/Auth0 if you’re targeting larger enterprises directly
  • Microsoft Entra ID / Google Workspace support if your customers are mostly on those ecosystems

What I recommend by scenario

1) Early-stage SaaS, want to move fast

Use WorkOS
Best if you need:

• SAML SSO
• SCIM provisioning
• Enterprise directory integration
• A clean developer experience

Why:

• It removes a lot of enterprise auth complexity
• Easier than implementing SAML yourself
• Good for SaaS products selling to mid-market/enterprise

2) Need a full auth platform

Use Auth0 Best if you need:

• Customer login
• Social login
• SSO
• MFA
• User management features

Why:

• Very flexible
• Mature ecosystem
• Good if auth is a core product area

Tradeoff:

• Can get expensive
• More platform complexity than a focused SSO layer

3) Already on AWS / want DIY with control

Use Cognito + external SAML/OIDC integrations Best if:

• You already use AWS heavily
• You can tolerate more integration work
• You mainly need basic auth plus some enterprise SSO

Tradeoff:

• Less polished for enterprise SSO workflows
• More engineering effort to get a great B2B auth experience

4) Large enterprise customers

Support both OIDC and SAML Many enterprises still require SAML, even though OIDC is the modern default.
If your customers are enterprise IT teams, you’ll likely need:

• SAML 2.0
• OIDC
• SCIM provisioning
• Just-in-time user provisioning
• Domain discovery / IdP-initiated login support

My default architectural advice

For a SaaS app, do this:

• Use your own app session system
• Delegate login to an IdP via OIDC
• Add SAML for enterprise compatibility
• Support SCIM if you sell to businesses with IT admins
• Do not build custom SSO protocols yourself

How to choose quickly

Choose WorkOS if:

• You sell B2B
• You want SSO quickly
• You don’t want to become an identity expert
• You need enterprise-ready features without heavy platform work

Choose Auth0 if:

• You want a broader identity platform
• You need consumer + B2B auth in one place
• You’re okay with platform cost/complexity

Choose Okta if:

• You are an enterprise-heavy product
• You need strong enterprise trust/compatibility
• You’re okay with more vendor overhead

Choose build-your-own only if:

• You have a strong identity/security team
• You have unique compliance or architecture needs
• You’re prepared for ongoing maintenance

Practical recommendation

If you’re asking as a typical SaaS founder or engineer:

Start with WorkOS for enterprise SSO, use OIDC as the default, and add SAML + SCIM only when needed.

If you want, I can also give you:

1. a vendor comparison table,
2. a recommended stack for your specific SaaS,
3. or a step-by-step SSO implementation plan.