lichess.org

lichess.org is an open-source, self-hosted chess game server designed for real-time gameplay. The software provides a comprehensive environment for playing, studying, and analyzing chess through a web-based interface and a mobile application. It serves as a complete ecosystem for chess enthusiasts to compete and learn in a digital space.

Users can engage in various competitive and casual formats, including tournaments and simultaneous exhibitions. The platform includes tools for learning and improvement, such as a tactics trainer and a shared analysis board. It is deployed as a server application and accessed via modern web browsers, with specific support for Firefox, Chromium, Edge, Opera, and Safari.

Key features

• Real-time chess gameplay with a web client and mobile app
• Distributed computer analysis via fishnet and Stockfish
• Tactic trainer for skill development
• Tournament and simul organization tools
• Community forums and team management
• Shared analysis boards for game review
• Search engine for game archives
• Support for over 140 languages
• Public PGN database for all rated games

The server is written in Scala 3 and utilizes a modified Play framework. It employs an asynchronous architecture using Scala Futures and Akka streams to handle high volumes of traffic. Data storage is managed through MongoDB, which stores over 12 billion games, with elasticsearch used for indexing. WebSocket connections are handled by a dedicated server communicating via redis, while nginx serves as the proxy for HTTP and WebSocket traffic. The frontend is built with TypeScript, snabbdom, and Sass, while the core chess logic is contained in a dedicated scalachess submodule. The project also provides an HTTP API for integration into other applications and websites.

Lichess is a non-profit project licensed under the GNU Affero General Public License 3, providing a free environment for the global chess community.