Source Code

Lichess is free/libre open source software. You can download, read, use and modify every bit of source code.

Main server

lichess-org/lila Main backend and frontend (Scala)
lichess-org/lila modules Backend modules (Scala)
lichess-org/lila ui Frontend modules (TypeScript, Sass)
lichess-org/scalachess Rules of chess and its variants (Scala)
lichess-org/compression Compression algorithms for chess moves and clocks (Java)
lichess-org/chessground Frontend chess board (TypeScript)
hi-ogawa/Stockfish Stockfish compiled for cutting-edge browsers (C++, WebAssembly, JavaScript)
lichess-org/stockfish.wasm, lichess-org/stockfish.js Slower fallback versions of Stockfish for browsers (C++, WebAssembly, JavaScript)
lichess-org/pgn-viewer Embedded client-side PGN viewer

lichess-org/lila-ws WebSocket traffic (Scala)
lichess-org/lila-http (Rust)
lichess-org/lila-fishnet Fishnet move requests (Scala)
lichess-org/lila-search Search engine (Scala)
lichess-org/lila-openingexplorer (Rust)
lichess-org/lila-tablebase Tablebase (Rust)
lichess-org/lila-push Web Push service (Rust)
lichess-org/fishnet Distributed computer analysis, using official-stockfish/Stockfish and ianfab/Fairy-Stockfish, a Stockfish fork with chess variant support (Rust, C++)
lichess-org/lila-gif GIF generator for games and positions (Rust)
lichess-org/external-engine External chess engine for the analysis board
lichess-org/kaladin Machine Learning tool aimed at automating cheat detection using Insights
clarkerubber/irwin AI that learns cheating patterns to help mods (Python)
lichess-org/lila-ip2proxy Query database of known proxy IPs (Rust)
cyanfish/bbpPairings Swiss pairings (C++)
ornicar/lichess-puzzler Generate, review and classify chess puzzles (Python, TypeScript)
michael1241/discotron Discord integration for Patron status (Python)

lichess-org/api HTTP API documentation (read here)
ornicar/scalalib Misc Scala utilities
lichess-org/playframework-lila Trimmed down Play Framework fork
ornicar/cash Trimmed down cash.js fork
ornicar/lichess-db Generator for database.lichess.org (download all rated games and puzzles)
ornicar/lila-db-seed Import dummy data into a local database for lila development
lichess-org/chess-openings Aggregated data set of chess opening names
ShailChoksi/lichess-bot Bridge between HTTP API and chess engines
clarkerubber/Staunton-Pieces Original 3D rendered pieces, boards and trophies
arex1337/lichess-daily-puzzle-slack-app Slack app that posts the daily puzzle to the Slack channel in which it is installed
arex1337/lichesspuzzle Zulip bot that posts the daily puzzle to a specific Zulip stream
lichess-org/swiss-maker Script to generate swiss tournaments for your team using the Lichess API
thoas/picfit HTTP image server (go)

Here are all frontend modules from lichess-org/lila ui in Web Labels compatible format: