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♞ Lichess ♞

The forever free, ad-free, and open-source chess server

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What is Lichess?

Lichess is a free, open-source online chess platform that has served millions of chess players worldwide since 2010. Built with Scala 3 and TypeScript, it offers real-time multiplayer gameplay, tactical puzzles, tournaments, computer analysis, and a comprehensive HTTP API—all without ads or paywalls.

Real-time Games

Play chess with millions of players worldwide with WebSocket-powered real-time gameplay

Puzzles & Training

Improve your tactics with over 3 million chess puzzles and performance tracking

Tournaments

Join Arena, Swiss, and team battle tournaments with flexible scheduling

Computer Analysis

Analyze games with Stockfish powered by a distributed Fishnet cluster

Getting Started

Set up your development environment in minutes

Architecture

Understand the system design and components

API Reference

Explore the comprehensive HTTP API

Development Setup

Configure your local development environment

Contributing

Learn how to contribute to Lichess

Bot API

Build chess bots and automated players

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Key Features

Play correspondence, rapid, blitz, or bullet chess with players worldwide. WebSocket-powered gameplay ensures instant move delivery and smooth user experience.
Train with over 3 million tactical puzzles. Track your puzzle rating, review your performance, and practice specific themes or openings.
Create and join Arena tournaments, Swiss tournaments, and team battles. Support for multiple time controls, rating restrictions, and custom conditions.
Collaborate on chess analysis with interactive studies. Follow live broadcasts of major chess events with real-time game updates.
Get Stockfish analysis for your games via the distributed Fishnet cluster. Cloud-based analysis available for all users.
Access games, user profiles, tournaments, puzzles, and more via comprehensive REST API. Support for streaming endpoints and bot integration.
Available in over 140 languages thanks to community translations via Crowdin.
Licensed under AGPL-3.0. All code is publicly available and contributions are welcome.

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Technology Stack

Lichess uses a modern, scalable tech stack:
  • Backend: Scala 3 with Play Framework 2.8
  • Frontend: TypeScript with Snabbdom
  • Database: MongoDB (4.7+ billion games)
  • Search: Elasticsearch
  • Cache & Messaging: Redis
  • WebSockets: Separate WebSocket server (lila-ws)
  • Analysis: Stockfish via Fishnet cluster
Lichess is a non-profit, open-source project maintained by a team of volunteers and funded by user donations. All features are free and will remain free forever.

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