I’m building a mobile app with web admin and need one auth system across both, what should I pick?

For one auth system across a mobile app + web admin, the safest default choice is:

Pick: OAuth 2.1 / OpenID Connect (OIDC) with a hosted identity provider

Examples:

• Auth0
• Firebase Authentication
• AWS Cognito
• Clerk
• Supabase Auth
• Azure AD B2C / Entra External ID (if enterprise-oriented)

Why this is usually the best choice

It gives you:

• One login system for both mobile and web
• Secure token-based auth suitable for mobile apps
• SSO / social login / password login if needed
• Role-based access control for your admin panel
• Less security risk than rolling your own auth

What to use in each client

Mobile app

• Use Authorization Code Flow with PKCE
• Store tokens securely in:
  • iOS Keychain
  • Android Keystore / Encrypted Shared Preferences

Web admin

• Use the same OIDC provider
• Prefer httpOnly, secure cookies for the admin session if possible
• Or use token auth if you’re building a pure SPA, but cookies are often safer for admin apps

Good options by team size

Fastest to ship

• Firebase Auth or Clerk
  • Simple setup
  • Great DX
  • Good for startups and MVPs

More control / enterprise-ready

• Auth0 or AWS Cognito
  • Better for complex auth needs, orgs, roles, enterprise SSO
  • More configuration overhead

If your backend is already on Supabase

• Supabase Auth
  • Convenient if you’re already using Supabase

If you’re asking “should I use sessions or JWTs?”

For a cross-platform setup:

• OIDC tokens under the hood
• Cookie-based sessions for web admin
• Access/refresh tokens for mobile

That hybrid approach is very common and works well.

My practical recommendation

If you want the simplest reliable answer:

• Start with Clerk or Firebase Auth if you want speed
• Choose Auth0 if you expect complexity, enterprise users, or many integrations
• Use OIDC/OAuth2.1 as the underlying standard
• Use one backend authorization layer for both clients

If you want, I can recommend the best option based on:

1. your stack,
2. whether you need social login/SSO,
3. whether the admin panel is public or internal,
4. and your budget.