Authenticate Using GitHub with JavaScript

You can let your users authenticate with Firebase using their GitHub accounts by integrating GitHub authentication into your app. You can integrate GitHub authentication either by using the Firebase SDK to carry out the sign-in flow, or by carrying out the GitHub OAuth 2.0 flow manually and passing the resulting access token to Firebase.

Before you begin

Add Firebase to your JavaScript project.
Register your app as a developer application on GitHub and get your app's OAuth 2.0 Client ID and Client Secret.
Enable GitHub authentication:
1. In the Firebase console, open the Auth section.
2. On the Sign in method tab, enable the GitHub sign-in method and specify the OAuth 2.0 Client ID and Client Secret you got from GitHub.
3. Then, make sure your Firebase OAuth redirect URI (e.g. my-app-12345.firebaseapp.com/__/auth/handler) is set as your Authorization callback URL in your app's settings page on your GitHub app's config.

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 GitHub 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 GitHub provider object:

var provider = new firebase.auth.GithubAuthProvider();

Optional: Specify additional OAuth 2.0 scopes that you want to request from the authentication provider. To add a scope, call addScope. For example:
```
provider.addScope('repo');
```
See the authentication provider documentation.
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:
```
provider.setCustomParameters({
  'allow_signup': 'false'
});
```
Reserved required OAuth parameters are not allowed and will be ignored. See the authentication provider reference for more details.

Authenticate with Firebase using the GitHub provider object. You can prompt your users to sign in with their GitHub accounts either by opening a pop-up window or by redirecting to the sign-in page. The redirect method is preferred on mobile devices.

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

firebase.auth().signInWithPopup(provider).then(function(result) {
  // This gives you a GitHub Access Token. You can use it to access the GitHub API.
  var token = result.credential.accessToken;
  // The signed-in user info.
  var user = result.user;
  // ...
}).catch(function(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;
  // ...
});

Also notice that you can retrieve the GitHub provider's OAuth token which can be used to fetch additional data using the GitHub APIs.

This is also where you can catch and handle errors. For a list of error codes have a look at the Auth Reference Docs.

To sign in by redirecting to the sign-in page, call signInWithRedirect:

firebase.auth().signInWithRedirect(provider);

Then, you can also retrieve the GitHub provider's OAuth token by calling getRedirectResult when your page loads:

firebase.auth().getRedirectResult().then(function(result) {
  if (result.credential) {
    // This gives you a GitHub Access Token. You can use it to access the GitHub API.
    var token = result.credential.accessToken;
    // ...
  }
  // The signed-in user info.
  var user = result.user;
}).catch(function(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;
  // ...
});

This is also where you can catch and handle errors. For a list of error codes have a look at the Auth Reference Docs.

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 GitHub) with an email that already exists for another Firebase user's provider (such as Google), the error auth/account-exists-with-different-credential is thrown along with an AuthCredential object (GitHub access token). To complete the sign in to the intended provider, the user has to sign first to the existing provider (Google) and then link to the former AuthCredential (GitHub access token).

Popup mode

If you use signInWithPopup, you can handle auth/account-exists-with-different-credential errors with code like the following example:


// Step 1.
// User tries to sign in to GitHub.
auth.signInWithPopup(new firebase.auth.GithubAuthProvider()).catch(function(error) {
  // An error happened.
  if (error.code === 'auth/account-exists-with-different-credential') {
    // Step 2.
    // User's email already exists.
    // The pending GitHub credential.
    var pendingCred = error.credential;
    // The provider account's email address.
    var email = error.email;
    // Get sign-in methods for this email.
    auth.fetchSignInMethodsForEmail(email).then(function(methods) {
      // Step 3.
      // If the user has several sign-in methods,
      // the first method in the list will be the "recommended" method to use.
      if (methods[0] === 'password') {
        // Asks the user their password.
        // In real scenario, you should handle this asynchronously.
        var password = promptUserForPassword(); // TODO: implement promptUserForPassword.
        auth.signInWithEmailAndPassword(email, password).then(function(user) {
          // Step 4a.
          return user.linkWithCredential(pendingCred);
        }).then(function() {
          // GitHub account successfully linked to the existing Firebase user.
          goToApp();
        });
        return;
      }
      // All the other cases are external providers.
      // Construct provider object for that provider.
      // TODO: implement getProviderForProviderId.
      var provider = getProviderForProviderId(methods[0]);
      // At this point, you should let the user know that he already has an account
      // but with a different provider, and let him validate the fact he wants to
      // sign in with this provider.
      // Sign in to provider. Note: browsers usually block popup triggered asynchronously,
      // so in real scenario you should ask the user to click on a "continue" button
      // that will trigger the signInWithPopup.
      auth.signInWithPopup(provider).then(function(result) {
        // Remember that the user may have signed in with an account that has a different email
        // address than the first one. This can happen as Firebase doesn't control the provider's
        // sign in flow and the user is free to login using whichever account he owns.
        // Step 4b.
        // Link to GitHub credential.
        // As we have access to the pending credential, we can directly call the link method.
        result.user.linkAndRetrieveDataWithCredential(pendingCred).then(function(usercred) {
          // GitHub account successfully linked to the existing Firebase user.
          goToApp();
        });
      });
    });
  }
});

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).

Handle the sign-in flow manually

You can also authenticate with Firebase using a GitHub account by handling the sign-in flow by calling the GitHub OAuth 2.0 endpoints:

Integrate GitHub authentication into your app by following the developer's documentation. At the end of the GitHub sign-in flow, you will receive an OAuth 2.0 access token.
If you need to sign in on a Node.js application, send the OAuth access token to the Node.js application.
After a user successfully signs in with GitHub, exchange the OAuth 2.0 access token for a Firebase credential:
```
var credential = firebase.auth.GithubAuthProvider.credential(token);
```

Authenticate with Firebase using the Firebase credential:

firebase.auth().signInAndRetrieveDataWithCredential(credential).catch(function(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, you must whitelist your Chrome extension ID:

Open your project in the Firebase console.
In the Authentication section, open the Sign-in method page.
Add a URI like the following to the list of Authorized Domains:
```
chrome-extension://CHROME_EXTENSION_ID
```

Only popup operations (signInWithPopup and linkWithPopup) are available to Chrome extensions, as Chrome extensions cannot use HTTP redirects. You should call these methods from a background script rather than a browser action popup, as the authentication popup will cancel the browser action popup.

In your Chrome extension's manifest file make sure that you add the https://apis.google.com URL to the content_security_policy whitelist.

Customizing the redirect domain for GitHub 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 whitelisted for all supported OAuth providers. However, this means that users may see that domain while signing in to GitHub before redirecting back to the application: Continue to: https://my-app-12345.firebaseapp.com

To customize the URL in the message to show a custom domain: Continue to: https://auth.custom.domain.com

Create a CNAME record for your custom domain that points to your project's subdomain on firebaseapp.com:
```
auth.custom.domain.com CNAME my-app-12345.firebaseapp.com
```
Add your custom domain to the list of authorized domains in the Firebase console: auth.custom.domain.com.
In the GitHub 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:

firebase.auth().signOut().then(function() {
  // Sign-out successful.
}).catch(function(error) {
  // An error happened.
});