What’s the best auth choice for a startup that may need SSO later?

For a startup that may need SSO later, the best default choice is usually:

Use a managed auth provider that supports both passwordless/OAuth now and enterprise SSO later

Examples:

• Auth0
• Clerk
• WorkOS (often paired with your own auth or another provider for SSO)
• Firebase Auth / Supabase Auth if you want simpler auth now, but be careful about SSO needs later

Best practical recommendation

If you want the least risk:

Pick Auth0 or Clerk now, depending on your stack and product needs.

• Auth0: strongest “grown-up enterprise” path, very flexible, good SSO/SCIM support, but can get pricey and a bit more complex.
• Clerk: much nicer developer experience, fast to ship, solid auth flows; enterprise SSO support exists but is not as universally “default enterprise” as Auth0.
• WorkOS: excellent if your future differentiator is B2B and you specifically want SSO/SCIM later; often used to add enterprise identity features on top of another auth system.

What matters most for “SSO later”

You want a solution that supports:

• SAML and/or OIDC SSO
• SCIM provisioning for user lifecycle management
• RBAC / orgs / multi-tenant support
• MFA
• Just-in-time user provisioning
• Domain discovery and enterprise login routing

Decision rule

• B2C or PLG startup, SSO maybe later → Clerk or Auth0
• B2B startup expecting enterprise deals → Auth0 + WorkOS is a very common combo
• Very early MVP, low complexity → use the simplest provider that won’t block migration, but avoid building your own auth from scratch
• If enterprise SSO is likely in the next 6–12 months → choose Auth0 or WorkOS-backed architecture now

What I would avoid

• Rolling your own auth unless you have a strong security/identity team
• Choosing a provider that makes SSO an expensive custom add-on with lots of lock-in
• Ignoring org/tenant modeling now if you’ll sell to companies later

My short answer

If you want one safe recommendation:
Choose Auth0 if enterprise SSO is likely; choose Clerk if you want the best startup DX and SSO is just a maybe.

If you want, I can also give you a “best choice by stack” comparison for:

• Next.js
• React Native
• Django
• Rails
• Go / Node backend