firebase-auth-basics

Add a googleSignIn block under auth.providers in firebase.json with your brand name, support email, and authorized redirect URIs, then run firebase deploy --only auth. Alternatively, enable the Google provider directly in the Firebase Console under Authentication providers.

Add the firebase-auth dependency using the Firebase BoM in build.gradle.kts, initialize Firebase.auth in your Activity, and call signInWithEmailAndPassword or createUserWithEmailAndPassword. Check auth.currentUser in onStart to detect existing sessions.

The firebase_auth/unauthorized-domain error means your domain is not in the Authorized Domains list. Add the domain in the Firebase Console or firebase.json, using only the domain name like localhost without protocol or port.

google_sign_in 7.x requires initialize() with a clientId on web, otherwise the app hangs on a blank screen. The recommended workaround is skipping GoogleSignIn initialization on web and using Firebase Auth's signInWithPopup with GoogleAuthProvider instead.

Use request.auth in security rules: allow read, write: if request.auth != null restricts access to authenticated users. Compare request.auth.uid with a document path variable or field to enforce per-user ownership.

The crash occurs when Auth.auth() is initialized inline before FirebaseApp.configure() runs, such as in a SwiftUI @State property at the app root. Use lazy initialization or create the auth manager only after Firebase configuration completes.