You can integrate Firebase Authentication with a custom authentication system by
modifying your authentication server to produce custom signed tokens when a user
successfully signs in. Your app receives this token and uses it to authenticate
with Firebase.
Before you begin
- Add Firebase to your JavaScript project
.
- Get your project's server keys:
- Go to the
Service Accounts
page in your project's settings.
- Click
Generate New Private Key
at the bottom of the
Firebase Admin SDK
section of the
Service Accounts
page.
- The new service account's public/private key pair is automatically
saved on your computer. Copy this file to your authentication server.
Authenticate with Firebase
- When users sign in to your app, send their sign-in credentials (for
example, their username and password) to your authentication server. Your
server checks the credentials and returns a
custom
token
if they are valid.
- After you receive the custom token from your authentication server, pass
it to
signInWithCustomToken
to sign in the user:
Web modular API
import { getAuth, signInWithCustomToken } from "firebase/auth";
const auth = getAuth();
signInWithCustomToken(auth, token)
.then((userCredential) => {
// Signed in
const user = userCredential.user;
// ...
})
.catch((error) => {
const errorCode = error.code;
const errorMessage = error.message;
// ...
});
Web namespaced API
firebase.auth().signInWithCustomToken(token)
.then((userCredential) => {
// Signed in
var user = userCredential.user;
// ...
})
.catch((error) => {
var errorCode = error.code;
var errorMessage = error.message;
// ...
});
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.
});