phone authentication in android using Firebase Step 1: Add Firebase to your Android project Step 2: Add this line build.Gradle(project) // Top-level build file where you can add configuration options common to all sub-projects/modules. buildscript { repositories { google() jcenter() } dependencies { classpath "com.android.tools.build:gradle:4.1.1" classpath 'com.google.gms:google-services:4.3.5' // NOTE: Do not place your application dependencies here; they belong // in the individual module build.gradle files } } allprojects { repositories { google() jcenter() } } task clean( type : Delete) { delete rootProject . buildDir } Step 3: Add this dependency build.Gradle (app level) plugins { id 'com.android.application' } android { compileSdkVersion 30 buildToolsVersion "30.0.3" defaultConfig { applicationId "com.ruhul.firebasephone...