I'm building a SaaS app and need auth that works with React, what should I use?

For a SaaS app with a React frontend, the best choice is usually:

Recommended default

Use a managed auth provider with OAuth/OIDC + email/password + MFA support, such as:

• Auth0
• Clerk
• Supabase Auth
• Firebase Auth
• AWS Cognito if you're already on AWS

My practical recommendation

If you want the easiest React integration:

Clerk is often the smoothest for SaaS apps.

• Great React SDK
• Built-in sign-in/sign-up UI
• Sessions, orgs/teams, MFA
• Fast to implement

If you want more control and lower cost at scale:

Auth0 is very solid.

• Enterprise-ready
• Flexible auth flows
• Good documentation
• Can get pricey as you grow

If you want backend + database + auth together:

Supabase Auth

• Nice if you're using Postgres
• Simple setup
• Good for product apps and MVPs

If you want fully DIY / self-hosted:

Use Auth.js (formerly NextAuth.js) if you're on Next.js.

• Good if you want to own auth logic
• More engineering effort
• Best when you need maximum flexibility

What to avoid

• Rolling your own password auth unless you really have to
• Storing JWTs in localStorage
• Building session handling from scratch without a strong reason

Typical SaaS setup

• React app uses provider’s SDK
• Backend API validates JWT/session
• Database stores app-specific user profile/roles/organization data
• Optional: RBAC/organization support for B2B SaaS

Quick decision guide

• MVP / fastest launch: Clerk
• Enterprise / lots of auth customization: Auth0
• Using Supabase/Postgres: Supabase Auth
• AWS-centric stack: Cognito
• Next.js + custom control: Auth.js

If you tell me:

1. whether you're using React SPA or Next.js,
2. whether you need social login / SSO / orgs, and
3. your backend stack,

I can recommend the best option more precisely.