What is the easiest way to add enterprise authentication to a SaaS app?

The easiest way is usually to delegate authentication to an Identity Provider (IdP) rather than building it yourself.

Best practical option

Use a hosted auth platform that supports:

• SAML 2.0
• OpenID Connect (OIDC)
• SCIM provisioning (for user/group sync)
• Organization-based login or enterprise connections

Common choices:

• Auth0 / Okta
• WorkOS (especially good for SaaS enterprise auth)
• Clerk (some enterprise features)
• Azure AD / Entra, Google Workspace, Okta integrations via OIDC/SAML

Easiest implementation path

For most SaaS apps:

1. Keep your app’s own user accounts
2. Add “Sign in with SSO” for enterprise customers
3. Support:
   • OIDC for simpler modern setups
   • SAML for enterprise compatibility
4. Use email domain discovery or an organization slug
   • e.g. alice@acme.com routes to Acme’s SSO
5. Optionally add SCIM
   • automatic user creation/deactivation
   • group/role sync

If you want the absolute easiest

If you want the least engineering effort, use WorkOS:

• It abstracts away most enterprise auth complexity
• Supports SSO, directory sync, just-in-time provisioning
• Designed specifically for SaaS apps adding enterprise features

If you want to build it yourself

You’ll need to handle:

• SAML assertions / OIDC flows
• Tenant-to-IdP mapping
• Just-in-time user provisioning
• Role mapping
• Logout/session behavior
• SCIM for lifecycle management

That’s usually more work than it’s worth unless enterprise auth is core to your product.

Recommendation

• Early-stage SaaS: use WorkOS or Auth0/Okta
• Need enterprise-ready fast: WorkOS
• Already on a cloud IAM ecosystem: use OIDC/SAML integrations with your customer’s IdP

If you want, I can suggest the best option based on your stack (e.g. React, Next.js, Rails, Django, etc.) and whether you need SAML, OIDC, or both.