Lichess — The Forever Free Open Source Chess Server

Introduction

Lichess is a non-profit, ad-free online chess platform that handles millions of games per day. Built in Scala on the Play Framework, it demonstrates that a complex real-time web application can be fully open source while competing with commercial alternatives.

What Lichess Does

• Hosts real-time chess games with multiple time controls (bullet, blitz, rapid, classical)
• Provides puzzles, studies, analysis boards, and tournament systems
• Integrates Stockfish for server-side game analysis available to all users
• Offers a comprehensive REST and WebSocket API for third-party apps
• Supports team leagues, simultaneous exhibitions, and Swiss/Arena tournaments

Architecture Overview

Lichess runs on the Play Framework (Scala) with MongoDB as the primary datastore and Redis for caching and pub/sub. Real-time game communication uses WebSockets routed through a Rust-based service called lila-ws. The Fishnet distributed computing network offloads Stockfish analysis across volunteer machines. The frontend is TypeScript with Snabbdom for reactive DOM updates.

Self-Hosting & Configuration

• Requires JDK 21, sbt, MongoDB 6+, Redis 7+, and Node.js for asset compilation
• Use the lila-docker repository for a containerized development setup
• Configure via conf/application.conf for database URLs, ports, and feature flags
• Fishnet (analysis) and lila-ws (WebSocket) are separate services to deploy
• Development mode auto-reloads on Scala source changes via sbt

Key Features

• Entirely free with no ads, subscriptions, or pay-to-win features
• Sub-100ms move latency through optimized WebSocket infrastructure
• Built-in opening explorer with millions of master and Lichess games
• Accessibility-first design with screen reader support and keyboard navigation
• Transparent Glicko-2 rating system with public rating distribution data

Comparison with Similar Tools

• Chess.com — commercial with ads and premium tiers; Lichess is fully free and open source
• Scid — desktop-only database tool; Lichess is a full online multiplayer platform
• PyChess — smaller community, fewer features; Lichess has a much larger player base
• en-croissant — local analysis GUI; Lichess provides cloud analysis and multiplayer

FAQ

Q: How does Lichess sustain itself without ads? A: Through patron donations. The non-profit model keeps costs low with efficient infrastructure.

Q: Can I use the Lichess API for my own app? A: Yes, the API is free and well-documented. Rate limits are generous for authenticated requests.

Q: Is self-hosting practical for a club or school? A: Yes, though it requires several services. The Docker setup simplifies local deployment.

Q: What languages is Lichess available in? A: Over 80 languages via community translation on Crowdin.

Sources

• https://github.com/lichess-org/lila
• https://lichess.org/api