Updated example for log in with Google in an MV3 extension

[arun-mani-j]

Hii

Do you have an updated example for MV3 extension that shows how to do a "log in with Google"? The sample available at https://github.com/firebase/quickstart-js/blob/master/auth/chromextension/manifest.json points to MV2 which is no longer supported. Similarly many things seem to have changed in the last 10 years regarding the steps, links etc.

If you can point to a latest up-to-date example one can use to boilerplate a new extension with proper steps, it would be helpful.

Also is there a way to create an extension for Firefox and other browsers where offscreen documents is not supported?

Thank you.

[GiselleUlloa]

The example you linked is indeed outdated. It was built for Manifest V2, which is no longer supported, and relies on APIs that no longer work (such as oauth2 in the manifest and persistent background pages).

Current state (Manifest V3)

At the moment, there is no official Firebase Auth quickstart updated for MV3 extensions. The correct and currently working approach for Chrome / Chromium-based browsers is:

• Use Manifest V3
• Handle the OAuth flow manually using chrome.identity.launchWebAuthFlow
• Run the logic inside a service worker
• Exchange the returned OAuth access_token for Firebase credentials using
  GoogleAuthProvider.credential(null, accessToken)

Official documentation:

• Chrome Identity API (MV3):
  https://developer.chrome.com/docs/extensions/reference/identity/
• launchWebAuthFlow:
  https://developer.chrome.com/docs/extensions/reference/identity/#method-launchWebAuthFlow
• MV2 to MV3 migration guide:
  https://developer.chrome.com/docs/extensions/develop/migrate/mv2-deprecation/

The legacy pattern using chrome.identity.getAuthToken together with oauth2 in the manifest is no longer valid:

• https://developer.chrome.com/docs/extensions/mv3/intro/mv3-migration/

Firebase Auth + Google Sign-In in extensions

Firebase currently does not provide an official MV3-compatible example for Chrome extensions.

The supported approach today is:

• Perform Google OAuth manually
• Retrieve an OAuth access token
• Authenticate with Firebase using the Web SDK and
  GoogleAuthProvider.credential

References:

• Firebase Google Sign-In (Web):
  https://firebase.google.com/docs/auth/web/google-signin
• GoogleAuthProvider.credential reference:
  https://firebase.google.com/docs/reference/js/auth.googleauthprovider.credential

Firefox and other browsers

Firefox does not support:

• chrome.identity
• launchWebAuthFlow

Official reference:

• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Chrome_incompatibilities

As a result, the same native authentication flow cannot be implemented in Firefox.

The only truly cross-browser solution is:

• Use a backend intermediary
• Perform Google OAuth on the backend
• Mint a Firebase custom token
• Authenticate the extension using signInWithCustomToken

Reference:

• Firebase Custom Tokens:
  https://firebase.google.com/docs/auth/admin/create-custom-tokens

Conclusion

• The current quickstart should be clearly marked as deprecated
• Firebase does not yet offer an official MV3 example
• For Chrome, launchWebAuthFlow is the correct and supported approach
• For Firefox, a backend-based or web-based login flow is required

Publishing an official MV3-compatible quickstart would significantly reduce confusion for developers.