Hi Friends. In this tutorial, we will learn how to implement firebase phone authentication with it's origin. Digits is an Simple...

Firebase Phone Authentication - Example Firebase Phone Authentication - Example

Firebase Phone Authentication - Example

Firebase Phone Authentication - Example

Hi Friends. In this tutorial, we will learn how to implement firebase phone authentication with it's origin.

Digits is an Simple User Phone Authentication Service to create easy login experience. Now Digits is acquired by Google's Firebase and it provides free service for limited amount of authentication per month. However, if you need to sign in a very high volume of users with phone authentication, you might need to upgrade your pricing plan. See the pricing page. 

You can use Firebase Authentication to sign in a user by sending an SMS message to the user's phone. The user signs in using a one-time code contained in the SMS message.

Setup Firebase

To setup firebase in your project, read previous post. After setting up, open Authentication sign in method and enable phone authentication method.

You should Add SHA Fingerprint in your application. To get SHA Fingerprint use the following Code with Command Prompt in Windows
keytool -list -v -keystore "%USERPROFILE%\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android

Coding Part

Add the dependency for Firebase Authentication to your app-level build.gradle file:
dependencies {
    compile 'com.google.firebase:firebase-auth:11.0.0'
// Add to the bottom of the file
apply plugin: 'com.google.gms.google-services'
Add the dependency for Play Services to your project-level build.gradle file:
dependencies {
    classpath 'com.google.gms:google-services:3.1.0'

Send a verification code to the user's phone

To initiate phone number sign-in, present the user an interface that prompts them to type their phone number. Send OTP to user by pass their phone number to the PhoneAuthProvider.verifyPhoneNumber method to request that Firebase verify the user's phone number. For example,
                phoneNumber,        // Phone number to verify
                60,                 // Timeout duration
                TimeUnit.SECONDS,   // Unit of timeout
                this,               // Activity (for callback binding)
                mCallbacks);        // OnVerificationStateChangedCallbacks
mCallbacks is used to know the verification status and the callback method is implemented as in the following
mCallbacks = new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
    public void onVerificationCompleted(PhoneAuthCredential credential) {
        Log.d(TAG, "onVerificationCompleted:" + credential);

    public void onVerificationFailed(FirebaseException e) {
        Log.w(TAG, "onVerificationFailed", e);
        if (e instanceof FirebaseAuthInvalidCredentialsException) {
            mPhoneNumberField.setError("Invalid phone number.");
        } else if (e instanceof FirebaseTooManyRequestsException) {
            Snackbar.make(findViewById(android.R.id.content), "Quota exceeded.",

    public void onCodeSent(String verificationId,
                           PhoneAuthProvider.ForceResendingToken token) {
        Log.d(TAG, "onCodeSent:" + verificationId);
        mVerificationId = verificationId;
        mResendToken = token;
This method is called, when the user number verified successfully.

This method is called, when error occurred during verification.

onCodeSent(String verificationId, PhoneAuthProvider.ForceResendingToken)
This method is called when the verification code is send to user via SMS.

Create a PhoneAuthCredential object

The phone auth credits are created as in the following snippet
PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, code);
// verificationId can be found in onCodeSent function in callback functionality
// code is retrieved from SMS send by Firebase
Then we can verify and store the Phone Authentication user details by using the following method.
            .addOnCompleteListener(this, new OnCompleteListener() {
                public void onComplete(@NonNull Task task) {
                    if (task.isSuccessful()) {
                        Log.d(TAG, "signInWithCredential:success");
                        FirebaseUser user = task.getResult().getUser();
                        startActivity(new Intent(PhoneAuthActivity.this, MainActivity.class));
                    } else {
                        Log.w(TAG, "signInWithCredential:failure", task.getException());
                        if (task.getException() instanceof FirebaseAuthInvalidCredentialsException) {
                            mVerificationField.setError("Invalid code.");

Sign Out

To sign out from your Application just use signout method in your Auth method.
FirebaseAuth mAuth = FirebaseAuth.getInstance();

Download Code:

You can download the full source from the following Github link. If you Like this tutorial, Please star it in Github.
Download From Github

Post your doubts and comments in the comments section.  


  1. Great article buddy, just I couldn't understand why to create, verification textview and verify button, as it autoverify the code. waiting for your reply

    1. Hi Buddy, Thanks for the response.
      The Create Button used to trigger verification for your entered phone number.
      The Verification Button used to verify for your entered code against the entered phone number.
      Your can implement the auto verification with Read SMS option.

  2. Hi Mushtaq bro,
    I am getting this error, when I added the code in my project.
    NOTE :: I've already created the project on firebase and paste json file in app.

    com.google.firebase.auth.FirebaseAuthInvalidCredentialsException: The custom token corresponds to a different audience. [ App ID does not match requested project. ]

    1. By your comment I think you are trying to generate login to other device, if you are trying that then you couldn't do it as Firebase will verify the verificationid and token {you could check that from the logcat tagged onCodeSent:}

    2. Bro,

      Try this, https://firebase.google.com/docs/reference/android/com/google/firebase/auth/Firebas

  3. thank u so much for this tutorial

  4. When the user is signed out and redirected to a sign in screen where he enters the already verified phone number. Does the user get nother sms code or get instantly authenticated ?

  5. PID: 24926
    java.lang.NullPointerException: null reference
    at com.google.android.gms.common.internal.zzbo.zzu(Unknown Source)
    at com.google.firebase.auth.PhoneAuthProvider.verifyPhoneNumber(Unknown Source)
    at net.clamour.goups.chat.PhoneAuthActivity.startPhoneNumberVerification(PhoneAuthActivity.java:163)
    at net.clamour.goups.chat.PhoneAuthActivity.access$000(PhoneAuthActivity.java:35)
    at net.clamour.goups.chat.PhoneAuthActivity$1.run(PhoneAuthActivity.java:76)

  6. It is interesting to read your blog post and I am going to share it with my friends.aybabg

  7. By using Firebase some frequent functionalities like Login with Google,Facebook,Twitter are being very easy because it's almost readily available with firebase. Thank you!
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