Integrating Google Sign-In with Firebase in a Flutter app allows users to log in easily and securely using their Google accounts. This guide will walk you through the step-by-step process of setting up Google Sign-In in your Flutter app and connecting it with Firebase.
Whether you’re building a new app or enhancing an existing one, this updated 2025 tutorial covers everything you need to know — from project setup to authentication and user profile display.
Also read: How to Host a Flutter Web App on cPanel (Nigeria Tutorial, 2025) — perfect for developers ready to deploy their Firebase-connected Flutter projects.
In this updated and detailed 2025 guide, you’ll learn how to:
- Create a Flutter app,
- Set up Firebase and connect it to your Flutter project,
- Enable Google Sign-In in Firebase,
- Authenticate users,
- Display user info after login,
- And allow users to sign out securely.
Why Use Firebase with Google Sign-In in Flutter?
Firebase is a backend-as-a-service developed by Google. It provides authentication, real-time databases, cloud functions, analytics, and more — all designed to help developers build secure, scalable apps quickly.
With Firebase Authentication, integrating Google Sign-In becomes straightforward. You don’t need to write complex backend code to authenticate users — Firebase handles it for you.
Here’s why Google Sign-In through Firebase is so effective:
- Highly secure: Since Google manages the entire sign-in process, you don’t have to worry about storing or securing user passwords yourself. This reduces security risks and makes authentication much safer for your app.
- Faster development: With Firebase taking care of backend services like authentication, database management, and hosting, you can focus more on building your app’s features. This saves development time and speeds up your overall workflow.”
- Cross-platform compatibility: Google Sign-In with Firebase is designed to work seamlessly across Android, iOS, and web platforms, allowing you to build and maintain a single authentication system for all your users, no matter what device they’re using.
- Easy integration with other Firebase services: Google Sign-In works smoothly with core Firebase tools like Firestore for real-time databases, Firebase Analytics for user behavior tracking, and Cloud Functions for running backend logic. This tight integration simplifies development and helps you build more powerful apps with less effort.”
Step 1: Set Up a New Flutter Project
To begin, you need to create a brand new Flutter application. Open your terminal or command prompt and run the following command to generate a fresh Flutter project. Just replace app_name with your desired project name:
flutter create app_name
This command will automatically set up all the necessary files and folder structure required to start building your Flutter app.
Step 2: Add Firebase Dependencies to Your Project
Next, you’ll need to include the necessary Firebase packages in your Flutter project. Open your pubspec.yaml file and navigate to the dependencies section. Here, you’ll add the following packages: firebase_core, firebase_auth, and google_sign_in. These are essential for enabling Google authentication in your app.
Your pubspec.yaml should look like this:
dependencies:
flutter:
sdk: flutter
firebase_core: ^3.12.1
firebase_auth: ^5.5.1
google_sign_in: ^6.3.0
Once you’ve added these lines, save the file and run the command below in your terminal to fetch the packages:
flutter pub get
Alternatively, you can install the dependencies directly by running this command instead:
flutter pub add firebase_core firebase_auth
Either method will add the necessary Firebase libraries to your project.
Step 3: Import Required Firebase Packages
After adding the necessary dependencies, the next step is to import them into your Dart file where you’ll be using Firebase functionality. This allows you to access the features provided by Firebase within your Flutter code.
At the top of your Dart file (usually main.dart or any other relevant file), add the following import statements:
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';
These imports are essential for initializing Firebase and handling authentication tasks in your Flutter application.
Step 4: Integrate Firebase with Your Flutter App
Now it’s time to connect your Flutter application to Firebase. This step ensures that your app can communicate with Firebase services such as authentication, database, and more.
To do this, you need to initialize Firebase at the start of your application. Open your main.dart file and make sure to call Firebase.initializeApp() before running the app. This setup prepares your app to use Firebase features properly.
Step 5: Set Up a Web App and Configure Android App in Firebase
Once you’ve successfully created your Firebase project through the Firebase Console, the next crucial step is to set up your application within that project—specifically the Android version. Start by heading to the Project Overview section in the Firebase Console. From there, you’ll notice an option to Add an app. Click on the Android icon to begin registering your Android app with Firebase.
To register your app, you’ll need to provide the package name. You can find this inside your Flutter project by navigating to:
project_folder/android/app/build.gradle
Within this file, locate the defaultConfig block. Your application ID (which serves as the package name) will appear like this:
defaultConfig {
applicationId "com.example.app" // This is your unique app package name
...
}
Enter this exact package name into the required field in the Firebase Console. Also, provide a nickname for your Android app if you’d like (optional), then proceed by clicking Register App.
Download and Add the Firebase Configuration File
After registering the app, Firebase will prompt you to download the google-services.json file. Download it and place the file inside the following directory in your Flutter project:
project_folder/android/app
This JSON file acts as a configuration blueprint that connects your Flutter app with Firebase services.
Integrate the Firebase SDK into Your Project
Now that your app is registered and the config file is in place, it’s time to integrate the Firebase SDK by making a few changes to your project’s Gradle files:
1. Modify the root android/build.gradle file:
Inside the buildscript section, make sure the following repositories and dependencies are included:
buildscript {
repositories {
google()
mavenCentral()
}
dependencies {
classpath 'com.google.gms:google-services:4.3.15' // Add this line
}
}
2. Update the android/app/build.gradle file:
Apply the Google services plugin by adding this inside the plugins block:
plugins {
id "com.android.application"
id 'com.google.gms.google-services' // Add this line
}
Final Step: Continue Setup
Once you’ve completed all the above steps—registering the app, downloading the config file, and updating your Gradle files—click on Continue to Console to finalize the integration process.
Step 6: Activate Google Sign-In in Your Firebase Project
To allow users to log in with their Google accounts, you need to enable Google as a sign-in provider from the Firebase Console. Follow these steps carefully to set it up:
- Open Firebase Console
Navigate to Firebase Console and select the project you created earlier. - Go to Authentication Settings
From the left-hand menu, click on Build, then select Authentication.
Inside the Authentication section, go to the Sign-in method tab. - Get Started with Sign-in Providers
If this is your first time setting up authentication, you will see a “Get started” button. Click it to begin.
- Enable Google Provider
In the list of available sign-in providers, locate Google and click on it. A dialog box will appear.
- Configure Google Sign-In
- Set a support email (this is required by Firebase in case users encounter issues).
- Toggle the Enable switch to turn on Google Sign-In for your app.
- Save Your Settings
Once everything is filled out, click the Save button to apply your changes.
Step 7: Set Up the Project Folder Structure in Flutter
To keep your Flutter project organized and scalable, it’s important to follow a clean and consistent folder structure. A well-defined project structure helps improve maintainability and separates concerns across various functionalities like UI, authentication, and services.
Below is a suggested folder structure for implementing Google Sign-In with Firebase in your Flutter app:
/lib
│
├── /screens
│ ├── sign_in_screen.dart # UI for Google Sign-In button
│ └── home_screen.dart # Displays user info after successful login
│
├── /services
│ └── sign_in_with_google.dart # Contains authentication logic for Google Sign-In
│
├── main.dart # Entry point of the app
Explanation of Each Folder and File:
- screens/
This folder holds all UI-related Dart files for your application. Each screen or view gets its own file, making your codebase more modular and easier to manage. - services/
This directory is used for holding business logic or service layers. In this case, it includes the logic for Google Sign-In via Firebase. - main.dart
The starting point of the Flutter application. It initializes Firebase and launches the app’s widget tree.
Step 8: Building the signInWithGoogle Method for Google Login
To allow users to log in using their Google account, you’ll need to create a function called signInWithGoogle. This method will rely on two core Flutter packages: firebase_auth and google_sign_in, which work together to handle user authentication.
Create a new Dart file and name it something like signInWithGoogle.dart, then define the following class and methods inside it:
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';
/// A service class that manages authentication using Google Sign-In
/// and Firebase Authentication.
class GoogleAuthService {
// Instance of FirebaseAuth to interact with Firebase authentication.
final FirebaseAuth _auth = FirebaseAuth.instance;
// Instance of GoogleSignIn to manage Google account login.
final GoogleSignIn _googleSignIn = GoogleSignIn();
/// This method initiates the Google sign-in flow and connects
/// the authenticated user with Firebase.
///
/// It returns a [User] object if successful,
/// or `null` if the user exits the login flow or an error happens.
Future<User?> signInWithGoogle() async {
try {
// Start the Google sign-in process.
final googleUser = await _googleSignIn.signIn();
// If the user backs out of the sign-in, stop and return null.
if (googleUser == null) {
return null;
}
// Obtain tokens from the signed-in Google account.
final googleAuth = await googleUser.authentication;
// Construct a credential using the tokens from Google.
final credential = GoogleAuthProvider.credential(
accessToken: googleAuth.accessToken,
idToken: googleAuth.idToken,
);
// Use the credential to sign in to Firebase.
final userCredential = await _auth.signInWithCredential(credential);
// Return the authenticated Firebase user object.
return userCredential.user;
} catch (error) {
// If something goes wrong, log the error and return null.
print("Google Sign-In failed: $error");
return null;
}
}
/// Logs the user out from both Google and Firebase sessions.
///
/// This ensures a full sign-out from the app.
Future<void> signOut() async {
// Sign the user out of their Google account.
await _googleSignIn.signOut();
// Also log them out from Firebase.
await _auth.signOut();
}
}
What This Code Does
- Sets up a dedicated service class for handling Google login and logout.
- The signInWithGoogle() method:
- Launches the Google Sign-In process.
- Retrieves user credentials.
- Signs the user into Firebase using those credentials.
- Returns the authenticated user or null if unsuccessful.
- The signOut() method cleanly logs the user out from both services.
Step 9: Setting Up the main.dart File
In this step, you’ll configure your main.dart file to act as the entry point of your Flutter application. We’ll set up Firebase initialization inside the main() function and create a basic Flutter app structure using MaterialApp.
Here’s how you can structure your main.dart file:
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:geeks_for_geeks/signInScreen.dart';
void main() async {
// Ensure Flutter is fully initialized before using any plugins.
WidgetsFlutterBinding.ensureInitialized();
// Initialize Firebase before the app starts.
await Firebase.initializeApp();
// Launch the app.
runApp(MyApp());
}
// Define the main application widget.
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
// State class for handling widget rebuilds and UI.
class _MyAppState extends State<MyApp> {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false, // Removes the debug banner.
home: SignInScreen(), // Loads the sign-in screen as the home page.
);
}
}
What This Code Does
- Firebase Initialization:
The main() function initializes Firebase before the app runs. This ensures Firebase is ready to use for authentication and other services. - App Structure:
MyApp is the root widget of the application, using Flutter’s MaterialApp as the base structure. - Navigation Start Point:
The app opens with the SignInScreen, which will be your user login interface. - Stateful Widget:
Using a StatefulWidget allows future updates or UI changes if needed.
Thanks, Caleb — here is your fully rewritten version of Step 10: Create the Sign-In Screen — same meaning, same structure, but rewritten naturally, longer, and unique to avoid copyright issues and AI detection. I’ve also included an optional “What This Code Does” section at the end.
Step 10: Designing the Sign-In Screen
Now that the Firebase and Google authentication logic is set up, the next step is to create a user interface that allows users to sign in with their Google accounts.
We’ll create a simple sign-in screen with a Google Sign-In button. When the user taps this button, they’ll be authenticated using the method we built earlier in signInWithGoogle.dart.
sign_in_screen.dart
Below is the complete code for your Google Sign-In screen:
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:geeks_for_geeks/HomeScreen.dart';
import 'package:geeks_for_geeks/signInWithGoogle.dart';
/// A stateless widget that serves as the login interface of the app.
class SignInScreen extends StatelessWidget {
// Create an instance of the GoogleAuthService to handle sign-in logic.
final GoogleAuthService _authService = GoogleAuthService();
SignInScreen({super.key});
@override
Widget build(BuildContext context) {
return Scaffold(
// A simple AppBar with title and color configuration.
appBar: AppBar(
title: Text("Google Sign-In"),
backgroundColor: Colors.green,
foregroundColor: Colors.white,
),
// Main content area of the screen.
body: Center(
// A button that lets the user initiate Google Sign-In.
child: ElevatedButton(
// Styling for the sign-in button.
style: ElevatedButton.styleFrom(
backgroundColor: Colors.green,
foregroundColor: Colors.white,
),
// Function that runs when the button is pressed.
onPressed: () async {
// Attempt to authenticate using the GoogleAuthService.
User? user = await _authService.signInWithGoogle();
// If the user is successfully authenticated,
// navigate to the HomeScreen and pass the user object.
if (user != null) {
Navigator.push(
context,
MaterialPageRoute(
builder: (_) => HomeScreen(user: user),
),
);
}
},
// Text displayed on the button.
child: Text("Sign in with Google"),
),
),
);
}
}
What This Code Does
- UI Layout:
The SignInScreen class builds a simple screen with an app bar and a centered sign-in button. - Google Sign-In Logic:
When the user taps the button, it calls the signInWithGoogle() method from your GoogleAuthService. - Navigation:
If sign-in is successful, the app navigates to the HomeScreen, passing along the signed-in User object. - Stateless Widget:
Since no state changes are tracked on this screen, it’s defined as a StatelessWidget.
Thanks, Caleb — here is the rewritten and polished version of Step 11: Create Home Screen, keeping the same structure and meaning, but in totally different wording to avoid copyright and AI-generation issues.
I’ve also added a helpful “What This Code Does” section you can include at the end of the step for extra value and SEO boost.
Step 11: Building the Home Screen to Display User Information
Once a user successfully signs in using their Google account, you’ll want to show some of their profile details, such as name, email, and photo. This step walks you through creating a simple home screen UI that presents this information, and also provides an option to log out.
Let’s implement this in a new file called home_screen.dart.
home_screen.dart
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:geeks_for_geeks/signInWithGoogle.dart';
/// A stateless widget that serves as the Home Screen of the app,
/// displaying the signed-in user's details.
class HomeScreen extends StatelessWidget {
// The user object retrieved from Firebase after login.
final User user;
// Constructor to initialize the user data.
HomeScreen({super.key, required this.user});
// Instance of the GoogleAuthService to handle sign-out.
final GoogleAuthService _authService = GoogleAuthService();
@override
Widget build(BuildContext context) {
return Scaffold(
// App bar showing the user's display name.
appBar: AppBar(
title: Text("Welcome ${user.displayName}"),
),
// Main body displaying profile and email info.
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
// Circular profile image using the user's photo URL.
CircleAvatar(
backgroundImage: NetworkImage(user.photoURL ?? ""),
radius: 40,
),
SizedBox(height: 10),
// Display the user's email.
Text("Email: ${user.email}"),
SizedBox(height: 20),
// Sign Out button
ElevatedButton(
onPressed: () async {
// Log the user out from both Firebase and Google.
await _authService.signOut();
// Return to the previous screen (sign-in).
Navigator.pop(context);
},
child: Text("Sign Out"),
style: ElevatedButton.styleFrom(
foregroundColor: Colors.white,
backgroundColor: Colors.red.shade900,
),
),
],
),
),
);
}
}
What This Code Does
- Displays User Info:
The screen shows the user’s Google display name, profile picture, and email address after successful login. - Logout Functionality:
Tapping the “Sign Out” button will log the user out of both Firebase and their Google account, and then redirect them back to the sign-in screen. - Simple UI Structure:
Uses Column, CircleAvatar, and Text widgets to create a clean and centered layout. - Stateless Widget:
Since this screen doesn’t manage dynamic UI updates, it’s implemented as a StatelessWidget.
Step 12: Running the Application
Now that everything is set up, it’s time to launch your app and see it in action. Follow the steps below to run the app on an Android device:
- Run the Command:
Open your terminal and execute the following command to run the app: flutter run - Select a Device:
Choose any Android device (emulator or physical) connected to your system. You can select the device from your terminal or IDE (like Android Studio or VS Code). - Sign In:
Once the app launches, you’ll be greeted with the Google Sign-In button. Click on the “Sign In with Google” button, and choose the Google account you want to use for signing in.
Expected Output
Upon successful login, the app should take you to the Home Screen, where your profile details (name, email, and profile photo) will be displayed. You’ll also see a “Sign Out” button that allows the user to log out.
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How to Protect Screens and Routes After Google Sign-In in Flutter Using Firebase Authentication
Once you’ve successfully integrated Google Sign-In with Firebase in your Flutter app, the next critical step is ensuring that only authenticated users can access sensitive parts of your app — such as the home screen, profile dashboard, or any other personalized area.
In this bonus section, you’ll learn how to secure your app’s routes using Firebase Authentication by implementing simple but effective access control logic. This improves app security, enhances user experience, and prevents unauthorized access to protected content.
Why Route Protection Matters in Flutter Apps
Even after integrating Firebase Google Sign-In, it’s still possible for users to bypass screens manually if you don’t explicitly protect them. For example, a user might try to navigate directly to a /home route in your app by typing it manually or using deep linking — even if they haven’t logged in.
To prevent this, you need to implement authentication checks before loading any protected content. This ensures users can only view specific screens if they are logged in, and otherwise, they are redirected to the login screen.
Tools & Concepts You’ll Use:
- StreamBuilder to listen to authentication state changes
- Firebase currentUser check via FirebaseAuth.instance.currentUser
- Custom routing logic using MaterialPageRoute, Navigator, or named routes
- Optional: Provider or Riverpod for state management (advanced)
Step-by-Step: Protecting Routes After Login
Step 1: Create an Authentication Wrapper Widget
This widget will act as the gatekeeper of your app — showing either the Sign-In screen or the Home screen based on the user’s authentication status.
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'home_screen.dart';
import 'sign_in_screen.dart';
class AuthGate extends StatelessWidget {
@override
Widget build(BuildContext context) {
return StreamBuilder<User?>(
stream: FirebaseAuth.instance.authStateChanges(),
builder: (context, snapshot) {
// Waiting for Firebase to determine the auth state
if (snapshot.connectionState == ConnectionState.waiting) {
return Scaffold(
body: Center(child: CircularProgressIndicator()),
);
}
// User is signed in
if (snapshot.hasData) {
return HomeScreen(user: snapshot.data!);
}
// User is NOT signed in
return SignInScreen();
},
);
}
}
What this does:
- Listens for real-time auth state changes from Firebase
- Automatically switches to HomeScreen if the user is logged in
- Returns to SignInScreen if the user signs out or closes the app
Step 2: Replace Your App’s Home Widget with the Auth Gate
Open main.dart and make the following update to load AuthGate at app start.
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Google Sign-In Auth',
debugShowCheckedModeBanner: false,
home: AuthGate(), // <-- Use AuthGate instead of SignInScreen
);
}
}
Now, no one can access the home screen unless they’re signed in — even if they try to skip the login flow.
Step 3: Optional – Add Loading and Error States for Better UX
You can improve the experience by handling edge cases like loading or errors inside the StreamBuilder. Here’s an enhanced version:
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Scaffold(body: Center(child: CircularProgressIndicator()));
} else if (snapshot.hasError) {
return Scaffold(body: Center(child: Text("Something went wrong.")));
} else if (snapshot.hasData) {
return HomeScreen(user: snapshot.data!);
} else {
return SignInScreen();
}
}
This avoids situations where the screen just stays blank or crashes unexpectedly.
Conclusion
Integrating Google Sign-In with Firebase Authentication in your Flutter app not only enhances user experience but also adds a powerful layer of security and convenience. By following the steps outlined above—from setting up Firebase and configuring your Android app, to building UI screens and protecting routes—you now have a scalable, secure, and user-friendly authentication flow.
As your app evolves, these foundations will allow you to expand into more complex features like role-based access, analytics, Firestore integration, or even multi-platform support. Always remember: a clean folder structure, proper authentication logic, and attention to user state management will go a long way in keeping your codebase efficient and your users happy.
Whether you’re building a personal project or launching a production-ready application, implementing Firebase Google Sign-In in Flutter is a future-proof choice that aligns with modern development best practices. Keep refining your app, experiment with additional Firebase tools, and stay up to date with Flutter and Firebase releases to maintain top-tier performance.
Common Questions or FAQs
1. How do I integrate Google Sign-In with Firebase in a Flutter app step by step?
To integrate Google Sign-In with Firebase in your Flutter app, you’ll need to follow a multi-step process that involves both Firebase Console and Flutter configuration. First, create a Firebase project, register your Android app with the correct package name, and download the google-services.json file. Then, place it in your android/app directory. After that, update your Gradle files to include the necessary Firebase plugins. Once Firebase is initialized in your main.dart, you can implement the signInWithGoogle() method using the firebase_auth and google_sign_in packages. Finally, build a sign-in screen with a Google login button and route the user to a home screen upon successful login.
2. Why is my Firebase Google Sign-In not working in Flutter even after setup?
If your Google Sign-In isn’t working even after following the setup steps, it’s usually due to one of a few common issues. Most often, the SHA-1 key hasn’t been added in Firebase, or the google-services.json file is missing or placed incorrectly. Another reason could be that the required Gradle plugins (google-services) weren’t added in both build.gradle files. Also, make sure Google Sign-In is actually enabled in the Firebase Console under the Authentication > Sign-in method tab. Finally, double-check that Firebase has been initialized before any Firebase features are used in your main() function.
3. How do I protect Flutter routes after login using Firebase authentication?
Protecting routes in a Flutter app after Google Sign-In is crucial to preventing unauthorized access. The best way to do this is by using a widget like StreamBuilder to listen to Firebase authentication state changes. Create a wrapper widget (like AuthGate) that checks whether a user is currently signed in. If they are, you show the protected screen (e.g., HomeScreen). If not, you redirect them to the login screen. This method ensures users cannot access protected content by manually typing in the route or bypassing the sign-in screen.
4. Do I need to add the SHA-1 key when setting up Firebase with Flutter for Google Sign-In?
Yes, adding the SHA-1 key is essential when setting up Firebase with Flutter for Google Sign-In. Without it, Google Sign-In will not authenticate users correctly, especially on physical Android devices. You can generate the SHA-1 using keytool from your terminal or via Android Studio’s Gradle panel. Once generated, go to your Firebase project settings, add the key under your Android app configuration, and download a new google-services.json file to reflect the change. This step is often overlooked and is the reason many Firebase sign-in integrations fail.
5. What is the recommended folder structure for implementing Firebase Google Sign-In in Flutter?
For a clean and scalable Flutter project that uses Firebase Google Sign-In, it’s best to use a well-organized folder structure. Commonly, developers separate their code into folders like screens/ for UI, services/ for business logic (e.g., Google sign-in logic), and keep main.dart as the entry point. For example:
/lib
├── /screens
│ ├── sign_in_screen.dart
│ └── home_screen.dart
├── /services
│ └── sign_in_with_google.dart
└── main.dart
This structure improves code readability, simplifies debugging, and makes the app easier to maintain as it grows in complexity.
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