Stop Losing 86% of Mobile Users: Lazy Auth with Firebase (Tutorial)

Source: Dev.to

The $300 Million Problem 💸

The famous “$300 Million Button” case study proved that forcing users to register before checkout is a revenue killer. On mobile, the stats are even worse—up to 86 % of users abandon apps when hit with an immediate login wall.

Solution: Lazy Registration (or “Just‑in‑Time” auth).

In this quick tutorial, you’ll learn how to:

1. Log users in anonymously first, so they can start using the app without any friction.
2. Prompt for credentials only when they need to save their work, upgrading the anonymous account instead of creating a new one.

Implementing Anonymous Sign‑In with Firebase

Firebase provides a method to create temporary, persisted sessions without asking the user for any data.

Docs:

import { getAuth, signInAnonymously } from "firebase/auth";

const auth = getAuth();

// 1. Log them in silently
await signInAnonymously(auth);

// 2. Listen to the auth state (User ID persists on reload!)
auth.onAuthStateChanged((user) => {
  if (user && user.isAnonymous) {
    console.log("User is a Guest 👻", user.uid);
  }
});

Upgrading an Anonymous Account

When the user decides to sign up (e.g., to save settings), you don’t create a new account. Instead, you link the new credentials to the existing anonymous user, preserving the uid and all Firestore data attached to it.

Docs:

import { EmailAuthProvider, linkWithCredential } from "firebase/auth";

const upgradeAccount = async (email, password) => {
  const credential = EmailAuthProvider.credential(email, password);
  const user = auth.currentUser;

  try {
    // Merge the new credentials into the existing anonymous account
    const result = await linkWithCredential(user, credential);
    console.log("Guest upgraded to Permanent User! 🎉");
  } catch (error) {
    console.error("Error linking account:", error);
  }
};

Cleaning Up Abandoned Guest Accounts

A downside of anonymous auth is the potential buildup of thousands of unused guest accounts. You can automate their removal without writing custom scripts by enabling Google Cloud Identity Platform and setting an automatic deletion policy (e.g., delete anonymous users inactive for 30 days).

Docs:

(link to relevant documentation can be added here)

Further Reading

I wrote a detailed deep‑dive on my personal blog that covers:

• React Hooks implementation.
• Handling credential-already-in-use errors.
• Screenshots of the Identity Platform configuration.
• A live demo using my Windows CLI learning app.

👉 Read the full article with guiding screenshots: Lazy Registrations with Firebase

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Have you implemented deferred auth in your apps?