You can let your users authenticate with Firebase using their Google Accounts.
You can either use the Firebase SDK to carry out the Google sign-in flow, or
carry out the sign-in flow manually using the Sign In With Google library and
passing the resulting ID token to Firebase.
Before you begin
- Add Firebase to your JavaScript project
.
- Enable Google as a sign-in method in the Firebase console:
- In the
Firebase console
, open
the
Auth
section.
- On the
Sign in method
tab, enable the
Google
sign-in method
and click
Save
.
Handle the sign-in flow with the Firebase SDK
If you are building a web app, the easiest way to authenticate your users
with Firebase using their Google Accounts is to handle the sign-in flow with
the Firebase JavaScript SDK. (If you want to authenticate a user in Node.js
or other non-browser environment, you must handle the sign-in flow manually.)
To handle the sign-in flow with the Firebase JavaScript SDK, follow these
steps:
- Create an instance of the Google provider object:
Web modular API
import { GoogleAuthProvider } from "firebase/auth";
const provider = new GoogleAuthProvider();
Web namespaced API
var provider = new firebase.auth.GoogleAuthProvider();
- Optional
: Specify additional OAuth 2.0 scopes that you
want to request from the authentication provider. To add a scope, call
addScope
. For example:
Web modular API
provider.addScope('https://www.googleapis.com/auth/contacts.readonly');
Web namespaced API
provider.addScope('https://www.googleapis.com/auth/contacts.readonly');
See the
authentication provider
documentation
.
- Optional
: To localize the provider's OAuth flow to the user's preferred
language without explicitly passing the relevant custom OAuth parameters, update the language
code on the Auth instance before starting the OAuth flow. For example:
Web modular API
import { getAuth } from "firebase/auth";
const auth = getAuth();
auth.languageCode = 'it';
// To apply the default browser preference instead of explicitly setting it.
// auth.useDeviceLanguage();
Web namespaced API
firebase.auth().languageCode = 'it';
// To apply the default browser preference instead of explicitly setting it.
// firebase.auth().useDeviceLanguage();
- Optional
: Specify additional custom OAuth provider parameters
that you want to send with the OAuth request. To add a custom parameter, call
setCustomParameters
on the initialized provider with an object containing the key
as specified by the OAuth provider documentation and the corresponding value. For example:
Web modular API
provider.setCustomParameters({
'login_hint': 'user@example.com'
});
Web namespaced API
provider.setCustomParameters({
'login_hint': 'user@example.com'
});
Reserved required OAuth parameters are not allowed and will be ignored.
See the
authentication provider reference
for more details.
- Authenticate with Firebase using the Google provider object. You can
prompt your users to sign in with their Google Accounts either by opening a
pop-up window or by redirecting to the sign-in page. The redirect method is
preferred on mobile devices.
Handling account-exists-with-different-credential Errors
If you enabled the
One account per email address
setting in the
Firebase console
,
when a user tries to sign in a to a provider (such as Google) with an email that already
exists for another Firebase user's provider (such as Facebook), the error
auth/account-exists-with-different-credential
is thrown along with an
AuthCredential
object (Google ID token). To complete the sign in to the
intended provider, the user has to sign first to the existing provider (Facebook) and then link to the
former
AuthCredential
(Google ID token).
If you use
signInWithPopup
, you can handle
auth/account-exists-with-different-credential
errors with code like the following
example:
import {
getAuth,
linkWithCredential,
signInWithPopup,
GoogleAuthProvider,
} from "firebase/auth";
try {
// Step 1: User tries to sign in using Google.
let result = await signInWithPopup(getAuth(), new GoogleAuthProvider());
} catch (error) {
// Step 2: User's email already exists.
if (error.code === "auth/account-exists-with-different-credential") {
// The pending Google credential.
let pendingCred = error.credential;
// Step 3: Save the pending credential in temporary storage,
// Step 4: Let the user know that they already have an account
// but with a different provider, and let them choose another
// sign-in method.
}
}
// ...
try {
// Step 5: Sign the user in using their chosen method.
let result = await signInWithPopup(getAuth(), userSelectedProvider);
// Step 6: Link to the Google credential.
// TODO: implement `retrievePendingCred` for your app.
let pendingCred = retrievePendingCred();
if (pendingCred !== null) {
// As you have access to the pending credential, you can directly call the
// link method.
let user = await linkWithCredential(result.user, pendingCred);
}
// Step 7: Continue to app.
} catch (error) {
// ...
}
Redirect mode
This error is handled in a similar way in the redirect mode, with the difference that the pending
credential has to be cached between page redirects (for example, using session storage).
Advanced: Handle the sign-in flow manually
You can also authenticate with Firebase using a Google Account by handling
the sign-in flow with the Sign In With Google library:
- Integrate Sign In With Google into your app by following the
integration guide
.
Be sure to configure Google Sign-In with the Google Client ID generated for your Firebase project. You can find your project's Google Client ID in your Project's Developers Console
Credentials page
.
- In the sign-in result callback, exchange the ID token from the Google auth response for a Firebase credential and use it to authenticate with Firebase:
function handleCredentialResponse(response) {
// Build Firebase credential with the Google ID token.
const idToken = response.credential;
const credential = GoogleAuthProvider.credential(idToken);
// Sign in with credential from the Google user.
signInWithCredential(auth, credential).catch((error) => {
// Handle Errors here.
const errorCode = error.code;
const errorMessage = error.message;
// The email of the user's account used.
const email = error.email;
// The credential that was used.
const credential = GoogleAuthProvider.credentialFromError(error);
// ...
});
}
Advanced: Authenticate with Firebase in Node.js
To authenticate with Firebase in a Node.js application:
- Sign in the user with their Google Account and get the user's Google ID
token. You can accomplish this in several ways. For example:
- After you get the user's Google ID token, use it to build a Credential
object and then sign in the user with the credential:
Web modular API
import { getAuth, signInWithCredential, GoogleAuthProvider } from "firebase/auth";
// Build Firebase credential with the Google ID token.
const credential = GoogleAuthProvider.credential(id_token);
// Sign in with credential from the Google user.
const auth = getAuth();
signInWithCredential(auth, credential).catch((error) => {
// Handle Errors here.
const errorCode = error.code;
const errorMessage = error.message;
// The email of the user's account used.
const email = error.customData.email;
// The AuthCredential type that was used.
const credential = GoogleAuthProvider.credentialFromError(error);
// ...
});
Web namespaced API
// Build Firebase credential with the Google ID token.
var credential = firebase.auth.GoogleAuthProvider.credential(id_token);
// Sign in with credential from the Google user.
firebase.auth().signInWithCredential(credential).catch((error) => {
// Handle Errors here.
var errorCode = error.code;
var errorMessage = error.message;
// The email of the user's account used.
var email = error.email;
// The firebase.auth.AuthCredential type that was used.
var credential = error.credential;
// ...
});
Authenticate with Firebase in a Chrome extension
If you are building a Chrome extension app, see the
Offscreen Documents guide
.
Customizing the redirect domain for Google sign-in
On project creation, Firebase will provision a unique subdomain for your project:
https://my-app-12345.firebaseapp.com
.
This will also be used as the redirect mechanism for OAuth sign in. That domain would need to be
allowed for all supported OAuth providers. However, this means that users may see that
domain while signing in to Google before redirecting back to the application:
Continue to: https://my-app-12345.firebaseapp.com
.
To avoid displaying your subdomain, you can set up a custom domain with Firebase Hosting:
- Follow steps 1 through 3 in
Set up your domain for Hosting
. When you verify
your domain ownership, Hosting provisions an SSL certificate for your custom domain.
- Add your custom domain to the list of authorized domains in the
Firebase console
:
auth.custom.domain.com
.
- In the Google developer console or OAuth setup page, whitelist the URL of the redirect page,
which will be accessible on your custom domain:
https://auth.custom.domain.com/__/auth/handler
.
- When you initialize the JavaScript library, specify your custom domain with the
authDomain
field:
var config = {
apiKey: '...',
// Changed from 'my-app-12345.firebaseapp.com'.
authDomain: 'auth.custom.domain.com',
databaseURL: 'https://my-app-12345.firebaseio.com',
projectId: 'my-app-12345',
storageBucket: 'my-app-12345.appspot.com',
messagingSenderId: '1234567890'
};
firebase.initializeApp(config);
Next steps
After a user signs in for the first time, a new user account is created and
linked to the credentials—that is, the user name and password, phone
number, or auth provider information—the user signed in with. This new
account is stored as part of your Firebase project, and can be used to identify
a user across every app in your project, regardless of how the user signs in.
-
In your apps, the recommended way to know the auth status of your user is to
set an observer on the
Auth
object. You can then get the user's
basic profile information from the
User
object. See
Manage Users
.
In your Firebase Realtime Database and Cloud Storage
Security Rules
, you can
get the signed-in user's unique user ID from the
auth
variable,
and use it to control what data a user can access.
You can allow users to sign in to your app using multiple authentication
providers by
linking auth provider credentials to an
existing user account.
To sign out a user, call
signOut
:
Web modular API
import { getAuth, signOut } from "firebase/auth";
const auth = getAuth();
signOut(auth).then(() => {
// Sign-out successful.
}).catch((error) => {
// An error happened.
});
Web namespaced API
firebase.auth().signOut().then(() => {
// Sign-out successful.
}).catch((error) => {
// An error happened.
});