useLinkProvider

const { linkWithProvider, linkWithPassword } = useLinkProvider();

await linkWithProvider(new GoogleAuthProvider()); // guest -> Google account
await linkWithPassword(email, password); // guest -> email/password account

Returns

linkWithProvider(provider) links an OAuth provider via popup. linkWithPassword(email, password) links an email/password credential.

Both resolve to { success: true, user, credential } or a failure result. Also exposes loading and error.

Upgrading a guest

The classic use: turn an anonymous user from useAnonymousSignIn into a real account without losing their data. The uid stays the same, so everything they created still belongs to them.