Vue Router is the official routing library for Vue.js applications, providing client-side routing capabilities for single-page applications. The codebase implements core routing functionality including history management (HTML5, hash, memory), route matching and parsing, navigation guards, and components like RouterLink and RouterView. It features experimental additions such as data loaders for declarative data fetching tied to navigation, file-based routing via unplugin integration, and custom param parsers for type-safe route parameters. The architecture follows a modular design with clear separation between core router logic, history implementations, matcher systems, and experimental features. The monorepo structure includes the main router package, documentation site, playgrounds for testing/demo, and experimental playgrounds showcasing cutting-edge features.