Firebase Auth errorFirebase Auth: auth/multi-factor-auth-required

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Why sign-in stops, and the fix

1. 01

   The app shows a generic error

   “Sign the user in with their first factor, then catch the auth/multi-factor-auth-required error.” Firebase, Add multi-factor authentication to your web app

   The user typed the right password, but the app says sign-in failed. Handle this code before the generic error branch.

   import { getAuth, signInWithEmailAndPassword, getMultiFactorResolver } from 'firebase/auth';
   
   const auth = getAuth();
   try {
     await signInWithEmailAndPassword(auth, email, password);
   } catch (error) {
     if (error.code === 'auth/multi-factor-auth-required') {
       const resolver = getMultiFactorResolver(auth, error);
       showSecondFactorScreen(resolver.hints);
     }
   }

2. 02

   Only email sign-in handles it

   Google, Apple and other providers throw the same code. Add the handler to signInWithPopup, signInWithRedirect results and reauthentication calls too.

3. 03

   The SMS step is not set up

   “This error contains a resolver, hints on the enrolled second factors, and an underlying session proving the user successfully authenticated with the first factor.” Firebase, Add multi-factor authentication to your web app

   Phone second factors need a reCAPTCHA verifier and the resolver session to send the code. Build the PhoneInfoOptions from the selected hint and resolver.session.

4. 04

   Testers see it only on some accounts

   “MFA requires email verification.” Firebase, Add multi-factor authentication to your web app

   Also check: multi-factor sign-in needs Firebase Authentication with Identity Platform, and Firebase says MFA requires email verification. Only accounts that enrolled a second factor in that project see this error.

Checked against the vendor’s docs on November 9, 2026: Firebase docs: Add multi-factor authentication to your web app.

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Related: Firebase auth/requires-recent-login · Firebase auth/quota-exceeded · Firebase auth/invalid-credential · Firebase auth/billing-not-enabled