Link Multiple Auth Providers to an Account Using JavaScript

Important: There is a known issue that prevents linkWithCredentials() from working correctly in some projects. See the issue report for a workaround and the status of a fix.

You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account. Users are identifiable by the same Firebase user ID regardless of the authentication provider they used to sign in. For example, a user who signed in with a password can link a Google account and sign in with either method in the future. Or, an anonymous user can link a Facebook account and then, later, sign in with Facebook to continue using your app.

Before you begin

Add support for two or more authentication providers (possibly including anonymous authentication) to your app.

Link federated auth provider credentials to a user account

To link credentials from an auth provider such as Google or Facebook to an existing user account:

Get the AuthProvider object that corresponds to the provider you want to link to the user's account. Examples:

Web

import { GoogleAuthProvider, FacebookAuthProvider, TwitterAuthProvider, GithubAuthProvider } from "firebase/auth";

const googleProvider = new GoogleAuthProvider();
const facebookProvider = new FacebookAuthProvider();
const twitterProvider = new TwitterAuthProvider();
const githubProvider = new GithubAuthProvider();auth_get_providers.js

Web

var googleProvider = new firebase.auth.GoogleAuthProvider();
var facebookProvider = new firebase.auth.FacebookAuthProvider();
var twitterProvider = new firebase.auth.TwitterAuthProvider();
var githubProvider = new firebase.auth.GithubAuthProvider();link-multiple-accounts.js

Prompt the user to sign in with the provider you want to link. You can prompt your users to sign in either by opening a pop-up window or by redirecting to the provider's sign-in page. The redirect method is preferred on mobile devices.

To sign in with a pop-up window, call linkWithPopup:

Web

import { getAuth, linkWithPopup, GoogleAuthProvider } from "firebase/auth";
const provider = new GoogleAuthProvider();

const auth = getAuth();
linkWithPopup(auth.currentUser, provider).then((result) => {
  // Accounts successfully linked.
  const credential = GoogleAuthProvider.credentialFromResult(result);
  const user = result.user;
  // ...
}).catch((error) => {
  // Handle Errors here.
  // ...
});auth_link_with_popup.js

Web

auth.currentUser.linkWithPopup(provider).then((result) => {
  // Accounts successfully linked.
  var credential = result.credential;
  var user = result.user;
  // ...
}).catch((error) => {
  // Handle Errors here.
  // ...
});link-multiple-accounts.js

To sign in by redirecting to the provider's sign-in page, call linkWithRedirect: Follow the best practices when using `linkWithRedirect`.

Web

import { getAuth, linkWithRedirect, GoogleAuthProvider } from "firebase/auth";
const provider = new GoogleAuthProvider();

const auth = getAuth();
linkWithRedirect(auth.currentUser, provider)
  .then(/* ... */)
  .catch(/* ... */);auth_link_with_redirect.js

Web

auth.currentUser.linkWithRedirect(provider)
  .then(/* ... */)
  .catch(/* ... */);link-multiple-accounts.js

After the user signs in, they are redirected back to your page. Then, you can retrieve the sign-in result by calling getRedirectResult when your page loads:

Web

import { getRedirectResult } from "firebase/auth";
getRedirectResult(auth).then((result) => {
  const credential = GoogleAuthProvider.credentialFromResult(result);
  if (credential) {
    // Accounts successfully linked.
    const user = result.user;
    // ...
  }
}).catch((error) => {
  // Handle Errors here.
  // ...
});auth_get_redirect_result.js

Web

auth.getRedirectResult().then((result) => {
  if (result.credential) {
    // Accounts successfully linked.
    var credential = result.credential;
    var user = result.user;
    // ...
  }
}).catch((error) => {
  // Handle Errors here.
  // ...
});link-multiple-accounts.js

If the user is signed in successfully, the user's account with the provider is linked to the user's account in your Firebase project.

Account linking will fail if the credentials are already linked to another user account. In this situation, you must handle merging the accounts and associated data as appropriate for your app:

Web

import { getAuth, signInWithCredential, linkWithCredential, OAuthProvider } from "firebase/auth";

// The implementation of how you store your user data depends on your application
const repo = new MyUserDataRepo();

// Get reference to the currently signed-in user
const auth = getAuth();
const prevUser = auth.currentUser;

// Get the data which you will want to merge. This should be done now
// while the app is still signed in as this user.
const prevUserData = repo.get(prevUser);

// Delete the user's data now, we will restore it if the merge fails
repo.delete(prevUser);

// Sign in user with the account you want to link to
signInWithCredential(auth, newCredential).then((result) => {
  console.log("Sign In Success", result);
  const currentUser = result.user;
  const currentUserData = repo.get(currentUser);

  // Merge prevUser and currentUser data stored in Firebase.
  // Note: How you handle this is specific to your application
  const mergedData = repo.merge(prevUserData, currentUserData);

  const credential = OAuthProvider.credentialFromResult(result);
  return linkWithCredential(prevUser, credential)
    .then((linkResult) => {
      // Sign in with the newly linked credential
      const linkCredential = OAuthProvider.credentialFromResult(linkResult);
      return signInWithCredential(auth, linkCredential);
    })
    .then((signInResult) => {
      // Save the merged data to the new user
      repo.set(signInResult.user, mergedData);
    });
}).catch((error) => {
  // If there are errors we want to undo the data merge/deletion
  console.log("Sign In Error", error);
  repo.set(prevUser, prevUserData);
});auth_merge_accounts.js

Web

// The implementation of how you store your user data depends on your application
var repo = new MyUserDataRepo();

// Get reference to the currently signed-in user
var prevUser = auth.currentUser;

// Get the data which you will want to merge. This should be done now
// while the app is still signed in as this user.
var prevUserData = repo.get(prevUser);

// Delete the user's data now, we will restore it if the merge fails
repo.delete(prevUser);

// Sign in user with the account you want to link to
auth.signInWithCredential(newCredential).then((result) => {
  console.log("Sign In Success", result);
  var currentUser = result.user;
  var currentUserData = repo.get(currentUser);

  // Merge prevUser and currentUser data stored in Firebase.
  // Note: How you handle this is specific to your application
  var mergedData = repo.merge(prevUserData, currentUserData);

  return prevUser.linkWithCredential(result.credential)
    .then((linkResult) => {
      // Sign in with the newly linked credential
      return auth.signInWithCredential(linkResult.credential);
    })
    .then((signInResult) => {
      // Save the merged data to the new user
      repo.set(signInResult.user, mergedData);
    });
}).catch((error) => {
  // If there are errors we want to undo the data merge/deletion
  console.log("Sign In Error", error);
  repo.set(prevUser, prevUserData);
});link-multiple-accounts.js

Link email address and password credentials to a user account

To add email address and password credentials to an existing user account:

Sign in the user using any authentication provider or method.
Prompt the user for an email address and new password.

Create an AuthCredential object with the email address and password:

Web

import { EmailAuthProvider } from "firebase/auth";

const credential = EmailAuthProvider.credential(email, password);auth_make_email_credential.js

Web

var credential = firebase.auth.EmailAuthProvider.credential(email, password);link-multiple-accounts.js

Pass the AuthCredential object to the signed-in user's linkWithCredential method:

Web

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

const auth = getAuth();
linkWithCredential(auth.currentUser, credential)
  .then((usercred) => {
    const user = usercred.user;
    console.log("Account linking success", user);
  }).catch((error) => {
    console.log("Account linking error", error);
  });auth_simple_link.js

Web

auth.currentUser.linkWithCredential(credential)
  .then((usercred) => {
    var user = usercred.user;
    console.log("Account linking success", user);
  }).catch((error) => {
    console.log("Account linking error", error);
  });link-multiple-accounts.js

The call to linkWithCredential will fail if the credentials are already linked to another user account. In this situation, you must handle merging the accounts and associated data as appropriate for your app (see example above).

Unlink an auth provider from a user account

You can unlink an auth provider from an account, so that the user can no longer sign in with that provider.

To unlink an auth provider from a user account, pass the provider ID to the unlink method. You can get the provider IDs of the auth providers linked to a user from the providerData property.

Web

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

const auth = getAuth();
unlink(auth.currentUser, providerId).then(() => {
  // Auth provider unlinked from account
  // ...
}).catch((error) => {
  // An error happened
  // ...
});auth_unlink_provider.js

Web

user.unlink(providerId).then(() => {
  // Auth provider unlinked from account
  // ...
}).catch((error) => {
  // An error happened
  // ...
});link-multiple-accounts.js