Spotube is a cross-platform, open-source Spotify client built with Flutter. It provides a full-featured music player experience without requiring a Spotify Premium subscription by leveraging plugin-based metadata providers and audio sources (YouTube, Piped, Invidious, JioSaavn, etc.). The application supports local playback, playlist management, lyrics (synced and plain), downloads, scrobbling (Last.fm), remote device control via WebSocket, and extensive customization (themes, layouts, audio quality). It uses Riverpod for state management, auto_route for navigation, drift for local SQLite storage, and media_kit for audio playback. The architecture is modular with a plugin system for metadata and audio sources, making it extensible. The codebase is well-structured with reusable patterns like pagination mixins, universal image loading, and type converters. It is actively maintained with nightly builds and a large community.