Google Login in Flutter Using Firebase

Adding Google authentication to your Flutter app is one of the easiest ways to provide a fast, secure, and user-friendly login experience. With Firebase Authentication and Google Sign-In, you can integrate login functionality in just a few steps.

In this guide, you’ll learn how to implement Google Sign-In in Flutter step by step.

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Why Use Google Sign-In in Flutter?

• ✅ Fast login (no signup form)
• ✅ Secure authentication
• ✅ Trusted by users
• ✅ Easy integration with Firebase

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Prerequisites

Before starting, make sure you have:

• Flutter installed
• Firebase project created
• Android Studio setup
• SHA-1 key generated

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Step 1: Create Firebase Project

1. Go to Firebase Console
2. Click Add Project
3. Enter project name and create

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Step 2: Add Android App

• Add your package name
• Add SHA-1 key
• Download google-services.json
• Place it in:

android/app/

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Step 3: Enable Google Authentication

• Go to Firebase Console
• Click Authentication → Sign-in Method
• Enable Google

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Step 4: Add Dependencies

dependencies:
  firebase_core: latest_version
  firebase_auth: latest_version
  google_sign_in: latest_version

Run:

flutter pub get

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Step 5: Initialize Firebase

await Firebase.initializeApp();

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Step 6: Google Sign-In Code

Future<User?> signInWithGoogle() async {
  final GoogleSignInAccount? user = await GoogleSignIn().signIn();  if (user == null) return null;  final GoogleSignInAuthentication auth = await user.authentication;  final credential = GoogleAuthProvider.credential(
    accessToken: auth.accessToken,
    idToken: auth.idToken,
  );  final result =
      await FirebaseAuth.instance.signInWithCredential(credential);  return result.user;
}

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Step 7: Add Login Button

ElevatedButton(
  onPressed: () async {
    final user = await signInWithGoogle();
    print(user?.email);
  },
  child: Text("Sign in with Google"),
)

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Step 8: Logout

await GoogleSignIn().signOut();
await FirebaseAuth.instance.signOut();

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Common Errors & Fixes

❌ API Exception (10)

👉 Check SHA-1 and package name

❌ Login Cancelled

👉 Handle null user properly

❌ Firebase Not Initialized

👉 Call Firebase.initializeApp()

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Pro Tips

• Use StreamBuilder for auth state
• Store user data in Firestore
• Add loading indicator
• Use clean architecture

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Conclusion

Implementing Google Login in Flutter using Firebase is simple and powerful. It improves user experience and boosts app engagement.

Start integrating today and make your app more professional 🚀