Join us in person and online for Firebase Summit on October 18, 2022. Learn how Firebase can help you accelerate app development, release your app with confidence, and scale with ease. Register now

Authenticate with Firebase Anonymously on Android

Stay organized with collections Save and categorize content based on your preferences.

You can use Firebase Authentication to create and use temporary anonymous accounts to authenticate with Firebase. These temporary anonymous accounts can be used to allow users who haven't yet signed up to your app to work with data protected by security rules. If an anonymous user decides to sign up to your app, you can link their sign-in credentials to the anonymous account so that they can continue to work with their protected data in future sessions.

Before you begin

  1. If you haven't already, add Firebase to your Android project.
  2. 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.

    Java

    dependencies {
        // Import the BoM for the Firebase platform
        implementation platform('com.google.firebase:firebase-bom:30.4.1')
    
        // 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'
    }
    

    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:21.0.8'
    }
    

    Kotlin+KTX

    dependencies {
        // Import the BoM for the Firebase platform
        implementation platform('com.google.firebase:firebase-bom:30.4.1')
    
        // 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'
    }
    

    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:21.0.8'
    }
    
  3. If you haven't yet connected your app to your Firebase project, do so from the Firebase console.
  4. Enable anonymous auth:
    1. In the Firebase console, open the Auth section.
    2. On the Sign-in Methods page, enable the Anonymous sign-in method.
    3. Optional: If you've upgraded your project to Firebase Authentication with Identity Platform, you can enable automatic clean-up. When you enable this setting, anonymous accounts older than 30 days will be automatically deleted. In projects with automatic clean-up enabled, anonymous authentication will no longer count toward usage limits or billing quotas. See Automatic clean-up.

Authenticate with Firebase anonymously

When a signed-out user uses an app feature that requires authentication with Firebase, sign in the user anonymously by completing the following steps:

  1. In your activity's onCreate method, get the shared instance of the FirebaseAuth object:

    Java

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

    Kotlin+KTX

    private lateinit var auth: FirebaseAuth
    // ...
    // Initialize Firebase Auth
    auth = Firebase.auth
  2. When initializing your Activity, check to see if the user is currently signed in:

    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);
    }

    Kotlin+KTX

    public override fun onStart() {
        super.onStart()
        // Check if user is signed in (non-null) and update UI accordingly.
        val currentUser = auth.currentUser
        updateUI(currentUser)
    }
  3. Finally, call signInAnonymously to sign in as an anonymous user:

    Java

    mAuth.signInAnonymously()
            .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, "signInAnonymously:success");
                        FirebaseUser user = mAuth.getCurrentUser();
                        updateUI(user);
                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w(TAG, "signInAnonymously:failure", task.getException());
                        Toast.makeText(AnonymousAuthActivity.this, "Authentication failed.",
                                Toast.LENGTH_SHORT).show();
                        updateUI(null);
                    }
                }
            });

    Kotlin+KTX

    auth.signInAnonymously()
            .addOnCompleteListener(this) { task ->
                if (task.isSuccessful) {
                    // Sign in success, update UI with the signed-in user's information
                    Log.d(TAG, "signInAnonymously:success")
                    val user = auth.currentUser
                    updateUI(user)
                } else {
                    // If sign in fails, display a message to the user.
                    Log.w(TAG, "signInAnonymously:failure", task.exception)
                    Toast.makeText(baseContext, "Authentication failed.",
                            Toast.LENGTH_SHORT).show()
                    updateUI(null)
                }
            }
    If sign-in succeeds you can use the getCurrentUser method to get the user's account data.

Convert an anonymous account to a permanent account

When an anonymous user signs up to your app, you might want to allow them to continue their work with their new account—for example, you might want to make the items the user added to their shopping cart before they signed up available in their new account's shopping cart. To do so, complete the following steps:

  1. When the user signs up, complete the sign-in flow for the user's authentication provider up to, but not including, calling one of the FirebaseAuth.signInWith methods. For example, get the user's Google ID token, Facebook access token, or email address and password.
  2. Get an AuthCredential for the new authentication provider:

    Google Sign-In

    Java

    AuthCredential credential = GoogleAuthProvider.getCredential(googleIdToken, null);

    Kotlin+KTX

    val credential = GoogleAuthProvider.getCredential(googleIdToken, null)
    Facebook Login

    Java

    AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());

    Kotlin+KTX

    val credential = FacebookAuthProvider.getCredential(token.token)
    Email-password sign-in

    Java

    AuthCredential credential = EmailAuthProvider.getCredential(email, password);

    Kotlin+KTX

    val credential = EmailAuthProvider.getCredential(email, password)
  3. Pass the AuthCredential object to the sign-in user's linkWithCredential method:

    Java

    mAuth.getCurrentUser().linkWithCredential(credential)
            .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    if (task.isSuccessful()) {
                        Log.d(TAG, "linkWithCredential:success");
                        FirebaseUser user = task.getResult().getUser();
                        updateUI(user);
                    } else {
                        Log.w(TAG, "linkWithCredential:failure", task.getException());
                        Toast.makeText(AnonymousAuthActivity.this, "Authentication failed.",
                                Toast.LENGTH_SHORT).show();
                        updateUI(null);
                    }
                }
            });

    Kotlin+KTX

    auth.currentUser!!.linkWithCredential(credential)
            .addOnCompleteListener(this) { task ->
                if (task.isSuccessful) {
                    Log.d(TAG, "linkWithCredential:success")
                    val user = task.result?.user
                    updateUI(user)
                } else {
                    Log.w(TAG, "linkWithCredential:failure", task.exception)
                    Toast.makeText(baseContext, "Authentication failed.",
                            Toast.LENGTH_SHORT).show()
                    updateUI(null)
                }
            }

If the call to linkWithCredential succeeds, the user's new account can access the anonymous account's Firebase data.

Automatic clean-up

If you've upgraded your project to Firebase Authentication with Identity Platform, you can enable automatic clean-up in the Firebase console. When you enable this feature you allow, Firebase to automatically delete anonymous accounts older than 30 days. In projects with automatic clean-up enabled, anonymous authentication will not count toward usage limits or billing quotas.

  • Any anonymous accounts created after enabling automatic clean-up might be automatically deleted any time after 30 days post-creation.
  • Anonymous accounts created before enabling automatic clean-up will be eligible for automatic deletion starting 30 days after enabling automatic clean-up.
  • If you turn automatic clean-up off, any anonymous accounts scheduled to be deleted will remain scheduled to be deleted. These accounts do not count toward usage limits or billing quotas.
  • If you "upgrade" an anonymous account by linking it to any sign-in method, the account will not get automatically deleted.

If you want to see how many users will be affected before you enable this feature, and you've upgraded your project to Firebase Authentication with Identity Platform, you can filter by is_anon in Cloud Logging.

Next steps

Now that users can authenticate with Firebase, you can control their access to data in your Firebase database using Firebase rules.