You can use Firebase Authentication to let your users authenticate with Firebase using their email addresses and passwords, and to manage your app's password-based accounts.
Before you begin
If you haven't already, add Firebase to your Android project.
- If you haven't yet connected your app to your Firebase project, do so from the Firebase console.
- Enable Email/Password sign-in:
- In the Firebase console, open the Auth section.
- On the Sign in method tab, enable the Email/password sign-in method and click Save.
In your module (app-level) Gradle file (usually
<project>/<app-module>/build.gradle.kts
or<project>/<app-module>/build.gradle
), add the dependency for the Firebase Authentication library for Android. We recommend using the Firebase Android BoM to control library versioning.dependencies { // Import the BoM for the Firebase platform implementation(platform("com.google.firebase:firebase-bom:33.4.0")) // 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") }
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:23.0.0") }
Create a password-based account
To create a new user account with a password, complete the following steps in your app's sign-in activity:
- In your sign-up activity's
onCreate
method, get the shared instance of theFirebaseAuth
object:Kotlin+KTX
private lateinit var auth: FirebaseAuth // ... // Initialize Firebase Auth auth = Firebase.auth
Java
private FirebaseAuth mAuth; // ... // Initialize Firebase Auth mAuth = FirebaseAuth.getInstance();
- When initializing your Activity, check to see if the user is currently signed in:
Kotlin+KTX
public override fun onStart() { super.onStart() // Check if user is signed in (non-null) and update UI accordingly. val currentUser = auth.currentUser if (currentUser != null) { reload() } }
Java
@Override public void onStart() { super.onStart(); // Check if user is signed in (non-null) and update UI accordingly. FirebaseUser currentUser = mAuth.getCurrentUser(); if(currentUser != null){ reload(); } }
- When a new user signs up using your app's sign-up form, complete any new account validation steps that your app requires, such as verifying that the new account's password was correctly typed and meets your complexity requirements.
- Create a new account by passing the new user's email address and password
to
createUserWithEmailAndPassword
:Kotlin+KTX
auth.createUserWithEmailAndPassword(email, password) .addOnCompleteListener(this) { task -> if (task.isSuccessful) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "createUserWithEmail:success") val user = auth.currentUser updateUI(user) } else { // If sign in fails, display a message to the user. Log.w(TAG, "createUserWithEmail:failure", task.exception) Toast.makeText( baseContext, "Authentication failed.", Toast.LENGTH_SHORT, ).show() updateUI(null) } }
Java
mAuth.createUserWithEmailAndPassword(email, password) .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, "createUserWithEmail:success"); FirebaseUser user = mAuth.getCurrentUser(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "createUserWithEmail:failure", task.getException()); Toast.makeText(EmailPasswordActivity.this, "Authentication failed.", Toast.LENGTH_SHORT).show(); updateUI(null); } } });
getCurrentUser
method to get the user's account data.
Sign in a user with an email address and password
The steps for signing in a user with a password are similar to the steps for creating a new account. In your app's sign-in activity, do the following:
- In your sign-in activity's
onCreate
method, get the shared instance of theFirebaseAuth
object:Kotlin+KTX
private lateinit var auth: FirebaseAuth // ... // Initialize Firebase Auth auth = Firebase.auth
Java
private FirebaseAuth mAuth; // ... // Initialize Firebase Auth mAuth = FirebaseAuth.getInstance();
- When initializing your Activity, check to see if the user is currently signed in:
Kotlin+KTX
public override fun onStart() { super.onStart() // Check if user is signed in (non-null) and update UI accordingly. val currentUser = auth.currentUser if (currentUser != null) { reload() } }
Java
@Override public void onStart() { super.onStart(); // Check if user is signed in (non-null) and update UI accordingly. FirebaseUser currentUser = mAuth.getCurrentUser(); if(currentUser != null){ reload(); } }
- When a user signs in to your app, pass the user's email address and
password to
signInWithEmailAndPassword
:Kotlin+KTX
auth.signInWithEmailAndPassword(email, password) .addOnCompleteListener(this) { task -> if (task.isSuccessful) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "signInWithEmail:success") val user = auth.currentUser updateUI(user) } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithEmail:failure", task.exception) Toast.makeText( baseContext, "Authentication failed.", Toast.LENGTH_SHORT, ).show() updateUI(null) } }
Java
mAuth.signInWithEmailAndPassword(email, password) .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, "signInWithEmail:success"); FirebaseUser user = mAuth.getCurrentUser(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithEmail:failure", task.getException()); Toast.makeText(EmailPasswordActivity.this, "Authentication failed.", Toast.LENGTH_SHORT).show(); updateUI(null); } } });
FirebaseUser
to proceed.
Recommended: Enable email enumeration protection
Some Firebase Authentication methods that take email addresses as parameters throw specific errors if the email address is unregistered when it must be registered (for example, when signing in with an email address and password), or registered when it must be unused (for example, when changing a user's email address). While this can be helpful for suggesting specific remedies to users, it can also be abused by malicious actors to discover the email addresses registered by your users.
To mitigate this risk, we recommend you enable email enumeration protection
for your project using the Google Cloud gcloud
tool. Note that enabling this
feature changes Firebase Authentication's error reporting behavior: be sure your app
doesn't rely on the more specific errors.
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()
Java
FirebaseAuth.getInstance().signOut();