LiveSplit One is a cross-platform speedrun timer application, the successor to the classic LiveSplit timer. It runs as a Progressive Web App and as a Tauri desktop application, targeting Windows, Linux, and macOS. The core timing logic is compiled to WebAssembly via the 'livesplit-core' Rust library, while the UI is built with React 19, TypeScript, and Vite. The application provides a rich set of features for speedrunners: highly customizable split timers, real-time comparisons, layout editor with drag-and-drop, integrated leaderboards from Speedrun.com, global hotkeys (desktop only), always-on-top mode, WebSocket server for remote control, and support for multiple timekeeping methods (real time vs game time). Data persistence is handled via IndexedDB in the browser and the filesystem in Tauri. The codebase is well-structured with a clear separation between core logic (WASM), UI components, and platform-specific code, though some central components like 'LiveSplit.tsx' are large and could benefit from further decomposition.