backend
Firebase Errors
Firebase errors split by product: Auth (auth/email-already-in-use), Firestore (permission-denied, resource-exhausted), Cloud Functions (deadline-exceeded, unavailable), FCM (registration-token-not-registered).
Firebase Auth error codes use namespaced format like `auth/email-already-in-use`. Firestore uses gRPC codes (PERMISSION_DENIED, FAILED_PRECONDITION). Most production failures: missing security rules, FCM token expiration, Cloud Function cold starts hitting deadline, App Check token rejection.
Official docs
https://firebase.google.com/docs/auth/admin/errors
Status page
https://status.firebase.google.com/
Support
https://firebase.google.com/support