FirebaseUI-Android is an open-source library providing pre-built UI components for Firebase Authentication, Realtime Database, Cloud Firestore, and Cloud Storage. It is a multi-module Android library published on Maven Central. The primary module, `firebase-ui-auth`, has been rewritten in Jetpack Compose with Material 3, offering a high-level composable (`FirebaseAuthScreen`) and a Kotlin DSL for configuration. It supports 12+ identity providers (Google, Facebook, Email, Phone, Apple, etc.), multi-factor authentication (SMS/TOTP), credential linking, anonymous upgrade, and email link sign-in. The `firebase-ui-database` and `firebase-ui-firestore` modules provide RecyclerView adapters with paging support (AndroidX Paging 3) for displaying Firebase data. The `firebase-ui-storage` module integrates with Glide for loading images from Firebase Storage. A demo app and end-to-end tests against the Firebase Auth Emulator are included. Architecturally, the library is split into separate Gradle modules: `auth`, `database`, `firestore`, `storage`, `common`, and `lint`. The auth module uses Kotlin coroutines, StateFlow, and a sealed class state machine (`AuthState`) to manage authentication flows. The database/firestore modules are older Java-based implementations using lifecycle-aware adapters and observable arrays. The library maintains a version catalog (libs.versions.toml) with modern dependencies (Kotlin 2.4.10, AGP 9.3.0, Compose BOM 2026.06.01). Key entry points include `FirebaseAuthScreen` (Compose), `FirebaseAuthUI` (singleton for sign-out/delete/auth state), `AuthFlowController` (Activity-based alternative), `FirebaseRecyclerAdapter`/`FirestoreRecyclerAdapter`, and `FirebaseImageLoader` (Glide integration). The primary data flows involve Firebase SDKs for authentication, database listeners, and image loading. The library is designed to be embedded in host Android apps, handling complex auth flows with minimal developer effort. The codebase demonstrates strong craftsmanship in the auth module’s state machine and Compose UI, but shows signs of technical drift due to mixed UI generations (legacy XML layouts alongside new Compose), some deprecated API usage (e.g., `fetchSignInMethodsForEmail`, `startActivityForResult`), and incomplete localizations. The database/firestore modules are mature but use older patterns. Overall, the library is well-structured and actively maintained, with a beta version (10.0.0-beta04) indicating ongoing development.