Authentication for Mobile Apps: Clerk vs Auth0 vs Rolling Your Own

Authentication is the first feature every user touches and the one nobody notices until it fails: a magic link that never arrives, a Google sign-in that works on Android but not iOS, a session that expires mid-checkout, or an App Store rejection because the app offered Google login without an equivalent privacy-friendly option.

This guide compares the main approaches to mobile app authentication in 2026 (hosted providers such as Clerk, Auth0, Supabase Auth and Firebase Auth, versus building your own), and covers the decisions that matter in React Native: social login, passkeys, token handling, biometrics and the store rules that apply.

Key takeaways

• Hosted auth is the right default for most apps: faster to ship, safer, and maintained by specialists.
• Clerk offers polished prebuilt flows and a React Native SDK; Auth0 suits enterprise needs like SSO; Supabase Auth and Firebase Auth come bundled with their backends.
• Build your own only for unusual requirements or when costs at scale justify it, and use proven libraries even then.
• If you offer Google or Facebook login on iOS, offer an equivalent privacy-friendly option, which in practice usually means Sign in with Apple (guideline 4.8).
• Account deletion must be available in the app on both stores if users can create accounts.

The options compared

Feature sets and pricing change frequently, so check current documentation before committing.

When hosted auth is the right choice

Almost always at the start. Authentication involves password hashing, brute-force protection, email deliverability, token rotation, multi-factor flows, account recovery and constant security updates. Providers do this as their core business. You'd rather spend that time on your product.

Pick based on where the rest of your stack lives: Supabase Auth if your data is in Supabase, Firebase Auth if you're on Firebase, Clerk for fast, polished flows on a custom backend, Auth0 when enterprise customers need SSO and complex identity rules.

When to build your own

• Very specific requirements (unusual identity providers, regulated environments with strict data residency).
• Scale where per-user pricing becomes a significant cost.
• An existing user database and auth system you must integrate with.

Even then, don't write cryptography yourself. Use well-reviewed libraries for password hashing, JSON Web Tokens and OAuth, and keep sessions revocable on the server.

Social login and React Native authentication flows

Social sign-in (Google, Apple, Facebook) usually works through a browser session that returns to your app via a deep link, or through native SDKs:

• Configure redirect URLs and your app's URL scheme carefully; most "works on one platform only" bugs live here.
• Use native Sign in with Apple on iOS for the best experience.
• Test on real devices, including users who cancel halfway through.

Passkeys

Passkeys replace passwords with device-bound credentials confirmed by Face ID, fingerprint or the device passcode, and they sync across a user's devices. They're phishing-resistant and remove password resets. Many hosted providers now support them; if you're starting fresh, offering passkeys alongside email sign-in is a strong default for consumer apps.

Tokens and sessions on the device

• Store refresh tokens in secure storage (Keychain and Keystore), never in plain AsyncStorage.
• Keep access tokens short-lived and refresh them in one place in your API client.
• Revoke on the server when users sign out or change passwords.
• Use biometrics to protect sensitive actions within a session, not as a replacement for authentication.

From the field: I've implemented authentication with JWT, OAuth 2.0, Clerk, Auth0 and NextAuth depending on the stack, with RBAC and multi-tenancy where products need it. On Expetitle, four stakeholder types (buyers, sellers, realtors and brokers) each needed role-scoped dashboards, so identity and permissions had to be designed together.

Store rules that touch authentication

• Guideline 4.8 (Apple): if you use third-party or social login, also offer an equivalent login that limits data collection to name and email, lets users keep their email private, and doesn't track them without consent. Sign in with Apple meets these criteria.
• Account deletion (Apple 5.1.1(v) and Google Play): users who can create accounts must be able to delete them from inside the app.
• Demo accounts for review: provide working credentials for App Review and Google Play's App access section.

Common authentication mistakes

• Treating the app as the authority on who's signed in, without validating tokens on the server.
• Long-lived tokens with no rotation or revocation.
• Social login redirect URLs that differ between development and production builds.
• No way to recover an account when a user loses access to their social login.
• Forgetting that phone numbers and emails change: design account identity around a stable user ID.

OAuth and Google sign-in libraries

If you're not using a hosted provider's SDK, two libraries come up most. react-native-app-auth implements OAuth 2.0 and OpenID Connect with PKCE through the platform's secure browser, which suits enterprise identity providers. For Google sign-in specifically, @react-native-google-signin/google-signin uses Google's native SDKs, and Expo's expo-auth-session handles browser-based OAuth flows. All of them need a development build in Expo, and all of them hand you tokens your server must still verify.

FAQ

What is the best authentication for a React Native app?

For most apps, a hosted provider: Clerk for polished flows on a custom backend, Auth0 for enterprise and SSO needs, or the auth built into Supabase or Firebase if you use those backends. Build your own only for specific requirements, using proven libraries.

Do I need Sign in with Apple in my iOS app?

If you offer third-party or social logins such as Google or Facebook, Apple's guideline 4.8 requires an equivalent option that limits data collection, allows private email and avoids ad tracking. Sign in with Apple meets those requirements, which is why most apps add it.

Should I use passkeys in my mobile app?

For new consumer apps, offering passkeys is a strong choice: they're phishing-resistant, remove password resets and use Face ID or fingerprint. Keep a fallback such as email sign-in for users and devices that don't support them yet.

Where should I store tokens in a mobile app?

Store refresh tokens in the device's secure storage (iOS Keychain and Android Keystore) and keep access tokens short-lived, ideally in memory. Validate every token on the server and make sessions revocable.

Next steps

If you're choosing an auth provider or fixing a sign-in flow that's causing support tickets or store rejections, I can set it up properly across app, backend and store requirements. Get in touch, or see how I work as a full-stack developer.

Sources

• Clerk Expo SDK, Clerk
• Auth0 React Native, Auth0
• App Review Guidelines (4.8, 5.1.1), Apple
• Passkeys, Apple
• OWASP Authentication Cheat Sheet, OWASP