Authenticate with Google on Android

You can let your users authenticate with Firebase using their Google Accounts.

Before you begin

If you haven't already, add Firebase to your Android project.

In your module (app-level) Gradle file (usually <project>/<app-module>/build.gradle), add the dependency for the Firebase Authentication Android library. We recommend using the Firebase Android BoM to control library versioning.

Also, as part of setting up Firebase Authentication, you need to add the Google Play services SDK to your app.

Kotlin+KTX

dependencies {
    // Import the BoM for the Firebase platform
    implementation platform('com.google.firebase:firebase-bom:32.1.0')

    // Add the dependency for the Firebase Authentication library
    // When using the BoM, you don't specify versions in Firebase library dependencies
    implementation 'com.google.firebase:firebase-auth-ktx'

    // Also add the dependency for the Google Play services library and specify its version
    implementation 'com.google.android.gms:play-services-auth:20.5.0'
}

By using the Firebase Android BoM, your app will always use compatible versions of Firebase Android libraries.

(Alternative) Add Firebase library dependencies without using the BoM

If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line.

Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.

dependencies {
    // Add the dependency for the Firebase Authentication library
    // When NOT using the BoM, you must specify versions in Firebase library dependencies
    implementation 'com.google.firebase:firebase-auth-ktx:22.0.0'

    // Also add the dependency for the Google Play services library and specify its version
    implementation 'com.google.android.gms:play-services-auth:20.5.0'
}

Java

dependencies {
    // Import the BoM for the Firebase platform
    implementation platform('com.google.firebase:firebase-bom:32.1.0')

    // Add the dependency for the Firebase Authentication library
    // When using the BoM, you don't specify versions in Firebase library dependencies
    implementation 'com.google.firebase:firebase-auth'

    // Also add the dependency for the Google Play services library and specify its version
    implementation 'com.google.android.gms:play-services-auth:20.5.0'
}

By using the Firebase Android BoM, your app will always use compatible versions of Firebase Android libraries.

(Alternative) Add Firebase library dependencies without using the BoM

If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line.

Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.

dependencies {
    // Add the dependency for the Firebase Authentication library
    // When NOT using the BoM, you must specify versions in Firebase library dependencies
    implementation 'com.google.firebase:firebase-auth:22.0.0'

    // Also add the dependency for the Google Play services library and specify its version
    implementation 'com.google.android.gms:play-services-auth:20.5.0'
}

If you haven't yet specified your app's SHA fingerprint, do so from the Settings page of the Firebase console. Refer to Authenticating Your Client for details on how to get your app's SHA fingerprint.
Enable Google as a sign-in method in the Firebase console:
1. In the Firebase console, open the Auth section.
2. On the Sign in method tab, enable the Google sign-in method and click Save.
When prompted in the console, download the updated Firebase config file (google-services.json), which now contains the OAuth client information required for Google sign-in.
Move this updated config file into your Android Studio project, replacing the now-outdated corresponding config file. (See Add Firebase to your Android project.)

Authenticate with Firebase

Integrate Google One Tap sign-in into your app by following the steps on the Sign users in with their saved credentials page. When you configure the BeginSignInRequest object, call setGoogleIdTokenRequestOptions:

Kotlin+KTX

signInRequest = BeginSignInRequest.builder()
            .setGoogleIdTokenRequestOptions(
                BeginSignInRequest.GoogleIdTokenRequestOptions.builder()
                    .setSupported(true)
                    // Your server's client ID, not your Android client ID.
                    .setServerClientId(getString(R.string.your_web_client_id))
                    // Only show accounts previously used to sign in.
                    .setFilterByAuthorizedAccounts(true)
                    .build())
            .build()

Java

signInRequest = BeginSignInRequest.builder()
    .setGoogleIdTokenRequestOptions(GoogleIdTokenRequestOptions.builder()
            .setSupported(true)
            // Your server's client ID, not your Android client ID.
            .setServerClientId(getString(R.string.default_web_client_id))
            // Only show accounts previously used to sign in.
            .setFilterByAuthorizedAccounts(true)
            .build())
    .build();

You must pass your "server" client ID to the setGoogleIdTokenRequestOptions method. To find the OAuth 2.0 client ID:

Open the Credentials page in the GCP Console.
The Web application type client ID is your backend server's OAuth 2.0 client ID.

After you integrate Google Sign-In, your sign-in activity has code similar to the following:

Kotlin+KTX

class YourActivity : AppCompatActivity() {

    // ...
    private val REQ_ONE_TAP = 2  // Can be any integer unique to the Activity
    private var showOneTapUI = true
    // ...

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        when (requestCode) {
             REQ_ONE_TAP -> {
                try {
                    val credential = oneTapClient.getSignInCredentialFromIntent(data)
                    val idToken = credential.googleIdToken
                    when {
                        idToken != null -> {
                            // Got an ID token from Google. Use it to authenticate
                            // with Firebase.
                            Log.d(TAG, "Got ID token.")
                        }
                        else -> {
                            // Shouldn't happen.
                            Log.d(TAG, "No ID token!")
                        }
                    }
                } catch (e: ApiException) {
                    // ...
            }
        }
    }
    // ...
}

Java

public class YourActivity extends AppCompatActivity {

  // ...
  private static final int REQ_ONE_TAP = 2;  // Can be any integer unique to the Activity.
  private boolean showOneTapUI = true;
  // ...

  @Override
  protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
      super.onActivityResult(requestCode, resultCode, data);

      switch (requestCode) {
          case REQ_ONE_TAP:
              try {
                  SignInCredential credential = oneTapClient.getSignInCredentialFromIntent(data);
                  String idToken = credential.getGoogleIdToken();
                  if (idToken !=  null) {
                      // Got an ID token from Google. Use it to authenticate
                      // with Firebase.
                      Log.d(TAG, "Got ID token.");
                  }
              } catch (ApiException e) {
                  // ...
              }
              break;
      }
  }
}

In your sign-in activity's onCreate method, get the shared instance of the FirebaseAuth object:

Kotlin+KTX

private lateinit var auth: FirebaseAuth
// ...
// Initialize Firebase Auth
auth = Firebase.authGoogleSignInActivity.kt

Java

private FirebaseAuth mAuth;
// ...
// Initialize Firebase Auth
mAuth = FirebaseAuth.getInstance();GoogleSignInActivity.java

When initializing your Activity, check to see if the user is currently signed in:

Kotlin+KTX

override fun onStart() {
    super.onStart()
    // Check if user is signed in (non-null) and update UI accordingly.
    val currentUser = auth.currentUser
    updateUI(currentUser)
}GoogleSignInActivity.kt

Java

@Override
public void onStart() {
    super.onStart();
    // Check if user is signed in (non-null) and update UI accordingly.
    FirebaseUser currentUser = mAuth.getCurrentUser();
    updateUI(currentUser);
}GoogleSignInActivity.java

In your onActivityResult() handler (see step 1), get the user's Google ID token, exchange it for a Firebase credential, and authenticate with Firebase using the Firebase credential:

Kotlin+KTX

val googleCredential = oneTapClient.getSignInCredentialFromIntent(data)
val idToken = googleCredential.googleIdToken
when {
    idToken != null -> {
        // Got an ID token from Google. Use it to authenticate
        // with Firebase.
        val firebaseCredential = GoogleAuthProvider.getCredential(idToken, null)
        auth.signInWithCredential(firebaseCredential)
                .addOnCompleteListener(this) { task ->
                    if (task.isSuccessful) {
                        // Sign in success, update UI with the signed-in user's information
                        Log.d(TAG, "signInWithCredential:success")
                        val user = auth.currentUser
                        updateUI(user)
                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w(TAG, "signInWithCredential:failure", task.exception)
                        updateUI(null)
                    }
                }
    }
    else -> {
        // Shouldn't happen.
        Log.d(TAG, "No ID token!")
    }
}

Java

SignInCredential googleCredential = oneTapClient.getSignInCredentialFromIntent(data);
String idToken = googleCredential.getGoogleIdToken();
if (idToken !=  null) {
    // Got an ID token from Google. Use it to authenticate
    // with Firebase.
    AuthCredential firebaseCredential = GoogleAuthProvider.getCredential(idToken, null);
    mAuth.signInWithCredential(firebaseCredential)
            .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    if (task.isSuccessful()) {
                        // Sign in success, update UI with the signed-in user's information
                        Log.d(TAG, "signInWithCredential:success");
                        FirebaseUser user = mAuth.getCurrentUser();
                        updateUI(user);
                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w(TAG, "signInWithCredential:failure", task.getException());
                        updateUI(null);
                    }
                }
            });
}

If the call to signInWithCredential succeeds you can use the getCurrentUser method to get the user's account data.

Next steps

After a user signs in for the first time, a new user account is created and linked to the credentials—that is, the user name and password, phone number, or auth provider information—the user signed in with. This new account is stored as part of your Firebase project, and can be used to identify a user across every app in your project, regardless of how the user signs in.

In your apps, you can get the user's basic profile information from the FirebaseUser object. See Manage Users.
In your Firebase Realtime Database and Cloud Storage Security Rules, you can get the signed-in user's unique user ID from the auth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account.

To sign out a user, call signOut:

Kotlin+KTX

Firebase.auth.signOut()MainActivity.kt

Java

FirebaseAuth.getInstance().signOut();MainActivity.java