How to Fix “Component auth has not been registered yet” in React Native Expo with Firebase Auth

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If you’re building a mobile app with React Native, Expo, and Firebase Authentication, you might encounter the frustrating error: “Component auth has not been registered yet, js engine: hermes” on app launch. This issue often appears after upgrading to Expo SDK 53 or using Firebase’s JavaScript SDK (version 11.x.x or higher). Don’t worry—this comprehensive guide will explain why this error happens, how to fix it, and how to prevent it.

This article covers everything from diagnosing the issue to implementing solutions, complete with code examples, troubleshooting tips, and best practices for React Native Expo Firebase Authentication. Whether you’re a beginner or an experienced developer, you’ll find clear, actionable steps to get your app running smoothly.

What Causes the “Component auth has not been registered yet” Error?

This error typically occurs when the Firebase Authentication module fails to initialize properly in a React Native app built with Expo. The root cause often lies in how the Metro bundler (Expo’s default JavaScript bundler) resolves Firebase’s CommonJS (.cjs) files, especially after updates in Expo SDK 53 or Firebase JS SDK 11.x.x. Here are the main reasons this happens:

  • Metro’s Package Exports Handling: Expo SDK 53 introduced support for the package.json exports field, which can conflict with Firebase’s modular structure, preventing the auth component from registering correctly.
  • Incorrect Firebase SDK Usage: Mixing the Firebase JS SDK (firebase) with the React Native Firebase library (@react-native-firebase/*) can cause conflicts, leading to this error.
  • AsyncStorage Issues: Firebase Auth requires @react-native-async-storage/async-storage for persistence in React Native, and misconfiguration can trigger the error.
  • Outdated Dependencies or Cache: Stale caches or mismatched dependency versions can prevent proper module resolution.
  • Routing Misconfiguration: In apps using Expo Router, improper route setups (e.g., missing default exports in route files) can confuse Metro and trigger this error.

Let’s dive into the solutions, starting with the most effective fixes based on recent community insights and official documentation.

Step-by-Step Solutions to Fix the Error

Here are proven solutions to resolve the “Component auth has not been registered yet” error in your React Native Expo app with Firebase Authentication. Try these in order, testing your app after each step.

Solution 1: Update Metro Config for Firebase Compatibility

The most common fix is to modify your Metro configuration to handle Firebase’s .cjs files and disable the package.json exports field, which causes conflicts in Expo SDK 53.

Steps:

  1. Locate or Create metro.config.js: In your project’s root directory, check for a metro.config.js file. If it doesn’t exist, create one.
  2. Update the Config: Add the following code to ensure Metro resolves .cjs files and disables the exports field:
const { getDefaultConfig } = require('expo/metro-config');

module.exports = (() => {
  const config = getDefaultConfig(__dirname);
  const { resolver } = config;

  config.resolver.sourceExts.push('cjs'); // Add support for .cjs files
  config.resolver.unstable_enablePackageExports = false; // Disable package.json exports

  return config;
})();
  1. Clear Metro Cache: Run the following command to clear the cache and restart the development server:npx expo start --clear
  2. Test Your App: Launch your app using expo start or expo run:android/expo run:ios if using a development build.

Why This Works: The Firebase JS SDK uses CommonJS modules (.cjs) for React Native, and Metro’s default handling of the exports field in Expo SDK 53 can fail to resolve these modules correctly. Adding .cjs to sourceExts and disabling unstable_enablePackageExports ensures proper module resolution.

Solution 2: Verify Firebase Initialization

Incorrect Firebase setup can cause the auth component to fail registration. Ensure you’re initializing Firebase correctly with the singleton pattern and using @react-native-async-storage/async-storage for persistence.

Steps:

  1. Install AsyncStorage: If not already installed, add the AsyncStorage package:npm install @react-native-async-storage/async-storage
  2. Update firebase.js: In your Firebase configuration file (e.g., firebase.js or config/firebase.ts), use the following setup:
import { initializeApp, getApps } from 'firebase/app';
import { initializeAuth, getReactNativePersistence } from 'firebase/auth';
import AsyncStorage from '@react-native-async-storage/async-storage';
import { getFirestore } from 'firebase/firestore';

const firebaseConfig = {
  apiKey: 'YOUR_API_KEY',
  authDomain: 'YOUR_AUTH_DOMAIN',
  projectId: 'YOUR_PROJECT_ID',
  storageBucket: 'YOUR_STORAGE_BUCKET',
  messagingSenderId: 'YOUR_MESSAGING_SENDER_ID',
  appId: 'YOUR_APP_ID',
};

// Initialize Firebase only if no apps are initialized
const app = getApps().length === 0 ? initializeApp(firebaseConfig) : getApps()[0];

// Initialize Auth with AsyncStorage persistence
export const auth = initializeAuth(app, {
  persistence: getReactNativePersistence(AsyncStorage),
});

// Initialize Firestore (optional)
export const firestore = getFirestore(app);
  1. Check for Multiple Initializations: Ensure you’re not calling initializeAuth or getAuth multiple times in your codebase, as this can cause conflicts. Use a single firebase.js file to export the auth instance and import it wherever needed.
  2. Test Again: Clear the cache (npx expo start --clear) and run your app.

Why This Works: The singleton pattern prevents multiple Firebase app instances, and getReactNativePersistence ensures auth state persists across sessions, which is critical for React Native.

Solution 3: Remove Conflicting Firebase Libraries

Using both the Firebase JS SDK (firebase) and React Native Firebase (@react-native-firebase/*) in the same project can cause the error. You must choose one SDK. For Expo apps, the Firebase JS SDK is recommended unless you need native-specific features like Crashlytics.

Steps:

  1. Check package.json: Open your package.json and look for dependencies like @react-native-firebase/app or @react-native-firebase/auth.
  2. Uninstall React Native Firebase: If present, remove these dependencies:npm uninstall @react-native-firebase/app @react-native-firebase/auth
  3. Verify Firebase JS SDK: Ensure you have the Firebase JS SDK installed:npm install firebase@11.7.3
  4. Remove google-services.json: If you previously used React Native Firebase, delete the google-services.json (Android) and GoogleService-Info.plist (iOS) files from your project, as they’re not needed for the JS SDK.
  5. Clean and Rebuild:rm -rf node_modules package-lock.json npm install npx expo start --clear

Why This Works: The two Firebase libraries are incompatible and can cause module resolution conflicts, leading to the auth component error. Sticking to the JS SDK simplifies setup for Expo apps.

Solution 4: Fix Expo Router Configuration

If you’re using Expo Router, the error might stem from misconfigured routes, such as missing default exports in files like register.tsx or _layout.tsx.

Steps:

  1. Check Route Files: Ensure all route files in your app/ directory have a default export. For example, in app/(auth)/register.tsx:import React from 'react'; import { View, Text } from 'react-native'; export default function Register() { return ( <View> <Text>Register Screen</Text> </View> ); }
  2. Verify Layout Files: Ensure _layout.tsx has a default export, like:import { Slot } from 'expo-router'; export default function RootLayout() { return <Slot />; }
  3. Remove Extraneous Routes: If you see warnings like “Route ‘register’ is extraneous,” check for duplicate or unused routes in your app/ directory and remove them.
  4. Test Routing: Run npx expo start --clear to verify navigation works without errors.

Why This Works: Expo Router requires proper default exports for all route components. Missing exports can confuse Metro, triggering the auth error.

Solution 5: Downgrade or Pin Firebase Version

Some developers report that downgrading the Firebase JS SDK to a specific version (e.g., 10.x.x) resolves the issue, as newer versions (11.x.x) introduced changes that conflict with Expo SDK 53.

Steps:

  1. Uninstall Current Firebase:npm uninstall firebase
  2. Install a Specific Version:npm install firebase@10.12.2
  3. Update Firebase Imports: Ensure your firebase.js uses getAuth instead of initializeAuth for older versions:import { initializeApp, getApps } from 'firebase/app'; import { getAuth } from 'firebase/auth'; import AsyncStorage from '@react-native-async-storage/async-storage'; const firebaseConfig = { /* your config */ }; const app = getApps().length === 0 ? initializeApp(firebaseConfig) : getApps()[0]; export const auth = getAuth(app);
  4. Clean and Test:rm -rf node_modules package-lock.json npm install npx expo start --clear

Why This Works: Older Firebase versions avoid the .cjs module issues introduced in newer releases, making them more compatible with Expo SDK 53.

Additional Troubleshooting Tips

If the above solutions don’t work, try these additional checks:

  • Clear All Caches: Beyond Metro, clear npm/yarn cache and reset your project:npm cache clean --force npx expo start --clear npx expo prebuild --clean
  • Check for Circular Imports: Ensure your firebase.js file isn’t imported in a way that creates circular dependencies. Use a linter like ESLint to detect these.
  • Verify Node.js Version: Use Node.js 18.x or 20.x, as newer versions (e.g., 22.x) may cause compatibility issues.
  • Disable New Architecture: Expo SDK 53’s new Fabric architecture can conflict with Firebase. Disable it in app.json:{ "expo": { "experiments": { "newArchitecture": false } } }
  • Test on a Fresh Project: Create a new Expo project (npx create-expo-app) and replicate your Firebase setup to isolate the issue.

Best Practices for Firebase Auth in Expo

To prevent this error and ensure a smooth Firebase Authentication setup, follow these blogging tips for React Native developers:

  • Use the Firebase JS SDK: Stick to firebase for Expo apps unless you need native-specific features.
  • Always Clear Cache After Updates: Run npx expo start --clear after changing dependencies or configs.
  • Follow Singleton Pattern: Initialize Firebase once in a dedicated firebase.js file and export services like auth and firestore.
  • Keep Dependencies Updated: Regularly check for updates to expo, firebase, and @react-native-async-storage/async-storage using npm outdated.
  • Test on Real Devices: Simulators can sometimes mask issues. Use a development build (npx expo run:android or npx expo run:ios) for accurate testing.

Example: Complete Firebase Auth Setup

Here’s a full example of a working Firebase Authentication setup with Expo SDK 53, including a login screen and auth state management:

// firebase.js
import { initializeApp, getApps } from 'firebase/app';
import { initializeAuth, getReactNativePersistence } from 'firebase/auth';
import AsyncStorage from '@react-native-async-storage/async-storage';

const firebaseConfig = { /* your config */ };
const app = getApps().length === 0 ? initializeApp(firebaseConfig) : getApps()[0];
export const auth = initializeAuth(app, {
  persistence: getReactNativePersistence(AsyncStorage),
});

// AuthContext.js ascended
import React, { createContext, useState, useEffect } from 'react';
import { onAuthStateChanged } from 'firebase/auth';
import { auth } from './firebase';

export const AuthContext = createContext({});

export function AuthProvider({ children }) {
  const [user, setUser] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const unsub = onAuthStateChanged(auth, (u) => {
      setUser(u);
      setLoading(false);
    });
    return unsub;
  }, []);

  return (
    <AuthContext.Provider value={{ user, loading }}>
      {children}
    </AuthContext.Provider>
  );
}

// App.jsx
import React from 'react';
import { View, Text, TextInput, Button } from 'react-native';
import { AuthProvider, AuthContext } from './AuthContext';
import { signInWithEmailAndPassword } from 'firebase/auth';
import { auth } from './firebase';

function LoginScreen() {
  const { user } = React.useContext(AuthContext);
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');

  const handleLogin = () => {
    signInWithEmailAndPassword(auth, email, password)
      .then(() => alert('Logged in!'))
      .catch((error) => alert(error.message));
  };

  return (
    <View>
      <TextInput
        placeholder="Email"
        value={email}
        onChangeText={setEmail}
      />
      <TextInput
        placeholder="Password"
        value={password}
        onChangeText={setPassword}
        secureTextEntry
      />
      <Button title="Log In" onPress={handleLogin} />
    </View>
  );
}

export default function App() {
  return (
    <AuthProvider>
      <LoginScreen />
    </AuthProvider>
  );
}

Metro Config (ensure this is in metro.config.js as shown in Solution 1).

This setup uses the Context API to manage auth state and provides a simple login screen.

Common FAQs

Why does this error only appear on mobile and not the web?

The Firebase JS SDK uses different module resolution for web (ESM) versus React Native (CommonJS). The .cjs files used in React Native can conflict with Metro’s bundler in Expo SDK 53, causing the error on mobile but not web.

Can I use React Native Firebase instead?

Yes, but it requires native code and isn’t compatible with Expo Go. Use a development build and follow the React Native Firebase setup guide.

How do I know if I have conflicting Firebase libraries?

Check your package.json for both firebase and @react-native-firebase/*. Remove one to avoid conflicts.

What if I’m using TypeScript?

Ensure your TypeScript config (tsconfig.json) includes "module": "commonjs" and "allowJs": true to handle Firebase’s .cjs files.

Conclusion: Get Your App Back on Track

The “Component auth has not been registered yet” error in React Native Expo with Firebase Auth can be frustrating, but it’s fixable with the right steps. By updating your Metro config, ensuring proper Firebase initialization, removing conflicting libraries, and verifying Expo Router setups, you can resolve the issue quickly. Always test after each change and follow best practices to prevent future errors.

Ready to fix your app? Start with Solution 1 (Metro config update) and work through the steps. If you’re still stuck, share your setup details in the comments, and I’ll help troubleshoot!

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