10 Powerful Reasons to Use Firebase as Your Mobile App Backend in 2025

📘 Chapter 2: Firebase Authentication and User Management

🔍 Overview

Authentication is one of the most crucial aspects of any mobile or web application. It ensures security, personalizes user experiences, and enables access control. Firebase Authentication is a powerful service that simplifies the entire authentication process—be it email/password, social sign-ins, or even anonymous access—while maintaining top-tier security and ease of use.

In this chapter, we’ll explore Firebase Authentication in detail, how to implement it in your mobile app, manage users, and apply role-based access control using custom claims.

🔐 What is Firebase Authentication?

Firebase Authentication provides backend services, easy-to-use SDKs, and ready-made UI libraries to authenticate users to your app. It supports:

• Email and password login
• Phone number authentication
• Third-party providers (Google, Facebook, Twitter, Apple, etc.)
• Anonymous authentication
• Custom authentication systems

It also integrates seamlessly with Firestore, Realtime Database, and other Firebase services.

🔧 Why Use Firebase Auth?

🔹 Benefits:

• ✅ Quick setup with minimal code
• ✅ Secure login with token-based auth
• ✅ Supports multiple sign-in methods
• ✅ Ready-made and customizable UI flows
• ✅ Built-in session management
• ✅ Integration with Firebase Rules for access control

🧱 Firebase Auth Architecture

Firebase uses a token-based system built on OAuth 2.0 and JWT (JSON Web Tokens). Here’s a high-level architecture:

text

[User Interaction]

     ↓

[Firebase Auth SDK]

     ↓

[Authentication Provider (Google, Facebook, etc.)]

     ↓

[Firebase Auth Server]

     ↓

[Access Token Issued to App]

     ↓

[Used to Access Firestore, Realtime DB, etc.]

🧰 Supported Sign-In Methods

🚀 Setting Up Firebase Authentication

🔸 Step 1: Enable Sign-in Method

• Go to Firebase Console > Authentication > Sign-in method
• Enable your preferred methods (e.g., Google, Email/Password)

🔸 Step 2: Add Firebase Auth to Your App

Android (Java/Kotlin) Example:

groovy

// In build.gradle

implementation 'com.google.firebase:firebase-auth:22.1.0'

🔸 Step 3: Initialize Firebase in App

java

FirebaseAuth mAuth = FirebaseAuth.getInstance();

🧪 Code Samples

✅ Email/Password Signup

java

mAuth.createUserWithEmailAndPassword("test@example.com", "123456")

    .addOnCompleteListener(task -> {

        if (task.isSuccessful()) {

            FirebaseUser user = mAuth.getCurrentUser();

            Log.d("FirebaseAuth", "User Created: " + user.getEmail());

        } else {

            Log.w("FirebaseAuth", "Error: ", task.getException());

        }

    });

✅ Sign In with Email/Password

java

mAuth.signInWithEmailAndPassword("test@example.com", "123456")

    .addOnCompleteListener(task -> {

        if (task.isSuccessful()) {

            FirebaseUser user = mAuth.getCurrentUser();

            Log.d("FirebaseAuth", "Login Successful: " + user.getEmail());

        } else {

            Log.w("FirebaseAuth", "Login Failed: ", task.getException());

        }

    });

✅ Sign Out

java

mAuth.signOut();

✅ Get Current Logged-In User

java

FirebaseUser currentUser = mAuth.getCurrentUser();

if (currentUser != null) {

    String email = currentUser.getEmail();

    String uid = currentUser.getUid();

}

✅ Update User Profile

java

FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();

if (user != null) {

    UserProfileChangeRequest profileUpdates = new UserProfileChangeRequest.Builder()

        .setDisplayName("John Doe")

        .build();

    user.updateProfile(profileUpdates);

}

🔐 Role-Based Access Control with Custom Claims

Firebase Admin SDK (Node.js) allows setting custom claims like "admin", "editor", etc.

js

admin.auth().setCustomUserClaims(uid, { admin: true })

  .then(() => {

    console.log('Custom claim set for user');

  });

You can then use these claims in Firestore rules:

js

match /adminData/{docId} {

  allow read, write: if request.auth.token.admin == true;

}

📋 Firebase Authentication Management Table

🌐 Firebase Auth UI Library

Firebase also offers FirebaseUI—a drop-in authentication UI that handles sign-in flows for you.

groovy

implementation 'com.firebaseui:firebase-ui-auth:8.0.2'

You can then launch an auth intent like:

java

startActivityForResult(

    AuthUI.getInstance()

          .createSignInIntentBuilder()

          .setAvailableProviders(Arrays.asList(

              new AuthUI.IdpConfig.EmailBuilder().build(),

              new AuthUI.IdpConfig.GoogleBuilder().build()

          ))

          .build(),

    RC_SIGN_IN);

🔒 Securing Access with Authentication State

Firebase provides AuthStateListeners so you can redirect or protect screens based on login status.

java

FirebaseAuth.AuthStateListener mAuthListener = firebaseAuth -> {

    FirebaseUser user = firebaseAuth.getCurrentUser();

    if (user != null) {

        // User is signed in

    } else {

        // User is signed out

    }

};

📌 Conclusion

Firebase Authentication offers a robust, scalable, and developer-friendly authentication system that can be integrated in just minutes. Whether you’re building a small MVP or a global app, Firebase Auth provides the flexibility and security needed to manage users, sessions, roles, and access controls efficiently.

In the next chapter, we’ll explore Firebase’s databases: Realtime Database and Firestore—where you’ll learn how to store and sync user-generated content.