Google Sign-In in Flutter: Step-by-Step Guide (2025)

Prerequisites for Google Sign-In in Flutter

Before implementing Google authentication in Flutter, ensure you have:

• A Flutter development environment set up.
• An active Firebase account.
• A new or existing Flutter project ready to integrate with Firebase.

Step 1 – Set Up Your Flutter Project

Install Flutter and set up the development environment.

Create a new Flutter project:

flutter create my_project
  cd my_project

Open the project in your preferred code editor (e.g., VS Code or Android Studio).

Step 2 - Configure Firebase for Google Sign-In

• Go to the Firebase Console.
• Create a new Firebase project or select an existing one.
• Add your Android and iOS apps to the Firebase project.
• Download the necessary configuration files:
• google-services.json (Android) → Place in android/app/
• GoogleService-Info.plist (iOS) → Place in ios/Runner/
• Enable Google Sign-In in Firebase Authentication settings.

Step 3 - Add Dependencies to pubspec.yaml

Add the required packages for Firebase authentication and Google Sign-In:

dependencies:
    firebase_core: latest_version
    firebase_auth: latest_version
    google_sign_in: latest_version

Run the following command to install dependencies:

flutter pub get

Step 4 - Configure Android for Google Sign-In

• Modify android/build.gradle and android/app/build.gradle:
• Ensure the Google services plugin is applied.
• Update minSdkVersion if necessary.
• Add:

classpath 'com.google.gms:google-services:latest_version'

• Modify AndroidManifest.xml to include necessary configurations.

Step 5 - Configure iOS for Google Sign-In

Open ios/Runner/Info.plist and add the following:

<key>CFBundleURLTypes</key>
<array>
<dict>
<key>CFBundleURLSchemes</key>
<array>
<string>YOUR_REVERSED_CLIENT_ID</string>
</array>
</dict>
</array>

Replace YOUR_REVERSED_CLIENT_ID with the reversed client ID from GoogleService-Info.plist.

Step 6 – Initialize Firebase

Modify main.dart to initialize Firebase:

void main() async {
    WidgetsFlutterBinding.ensureInitialized();
    await Firebase.initializeApp();
    runApp(MyApp());
  }

Step 7 – Implement Google Sign-In in Flutter

Create a new file sign_in_demo.dart and add the following:

final GoogleSignIn googleSignIn = GoogleSignIn();
  final FirebaseAuth auth = FirebaseAuth.instance;
  
  Future signInWithGoogle() async {
    final GoogleSignInAccount? googleUser = await googleSignIn.signIn();
    final GoogleSignInAuthentication googleAuth = await googleUser!.authentication;
    final AuthCredential credential = GoogleAuthProvider.credential(
      accessToken: googleAuth.accessToken,
      idToken: googleAuth.idToken,
    );
    final UserCredential userCredential = await auth.signInWithCredential(credential);
    return userCredential.user;
  }

Add a Google Sign-In button and call signInWithGoogle() on tap.

Step 8 – Run Your App

Run the app on an emulator or physical device:

flutter run

Test Google Sign-In functionality to ensure proper authentication.

FAQs

Q1: How do I add Google Sign-In to my Flutter app?

A: Follow this guide step by step: Set up Firebase, configure dependencies, update Android/iOS settings, and implement sign-in logic in Dart.

Q2: Why is my Google login in Flutter not working?

A: Common issues include incorrect Firebase configuration, outdated dependencies, missing SHA keys, or incorrect OAuth settings.

Q3: Is Firebase required for Google login in Flutter?

A: Yes, Firebase Authentication simplifies Google Sign-In implementation and manages user authentication securely.

Conclusion

Google Sign-In in Flutter with Firebase provides a seamless authentication experience for your users. By following this guide, you can quickly set up and implement secure user authentication in your app.