How to set auth properly from user object gotten from the popup

[mukuljainx]

Hi, I am following the guide https://dev.to/lvn1/google-authentication-in-a-chrome-extension-with-firebase-2bmo, to get the user tokens for my extension, current issue is I am unable to set auth correctly from the user object, I don't see any such function as response only contains JSON, it is not possible to use the updateCurrentUser user function as well.

If anyone has faced the same issue, kindly guide!

[Chiragsd13]

The issue here is that Firebase Auth cannot reconstruct a User object from plain JSON — updateCurrentUser expects a proper User instance, not a serialized object.

In a Chrome extension, the right pattern is to pass the credential (not the user object) between contexts and call signInWithCredential in the extension:

// In your popup/background, after the Google sign-in succeeds:
const result = await signInWithPopup(auth, new GoogleAuthProvider());
const credential = GoogleAuthProvider.credentialFromResult(result);

// Serialize just the tokens (not the User)
chrome.storage.session.set({
  accessToken: credential.accessToken,
  idToken: credential.idToken
});

Then in your extension (service worker or content script):

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

const { accessToken, idToken } = await chrome.storage.session.get(["accessToken", "idToken"]);
const credential = GoogleAuthProvider.credential(idToken, accessToken);
const auth = getAuth();
await signInWithCredential(auth, credential);

// auth.currentUser is now properly set

This works because signInWithCredential re-authenticates properly on each side, giving you a real User object with all methods intact — rather than trying to hydrate one from JSON.

A few things to watch out for:

• accessToken from Google expires in 1 hour, so store the idToken too and refresh when needed
• Use chrome.storage.session (not local) so tokens are cleared when the browser closes
• If you need the token across service worker restarts, check auth.currentUser?.getIdToken() first before hitting storage