Built on other people’s good work.
A few pieces of free software and some open fonts ship with OpenPawn. Here is each one, who made it, and the licence it comes under.
Stockfish
The engine behind the coach. Every game review, live comment and mistakes-deck answer is checked by Stockfish, running in your browser.
- Version
- Stockfish 19, single-threaded WebAssembly builds from stockfish.js 19.0.1
- Files
stockfish-19-lite-single.jsandstockfish-19-lite-single.wasm, with the small net (1.8 MB), used everywhere.stockfish-19-single.jsandstockfish-19-single.wasm, with the full net (99 MB), only load when a page asks for them. All exactly as they come in the package.- Made by
- The Stockfish developers, starting with Tord Romstad, Marco Costalba, Joona Kiiski and Gary Linscott. Ported to WebAssembly by Nathan Rugg with Chess.com. Neural networks by Chris Bao and the Stockfish team.
- Stockfish source code github.com/official-stockfish/Stockfish
- Source of the build we ship github.com/nmrugg/stockfish.js, v19.0.1
- The npm package npmjs.com/package/stockfish, 19.0.1
- GNU GPL, version 3 Full text, served by us. Also at gnu.org/licenses/gpl-3.0
The GPL lets anyone use, study, share and change Stockfish. You can get the source code for the exact version we serve from the links above. The bots you play against don’t use Stockfish: Maia-3, below, chooses their moves, with a small engine we wrote ourselves as the backup.
Maia-3
The model behind the bots. It learned from real games on Lichess how people at each rating actually play, and chooses the bots’ moves on our own server.
- Version
- Maia3-5M, weights at revision b6559de on Hugging Face, read with the code at commit 1e13597
- Files
- The weights, converted to ONNX by our export script, which checks that the result answers exactly like the original. The model itself is unchanged.
- Made by
- Daniel Monroe, George Eilender, Philip Chalmers, Zhenwei Tang and Ashton Anderson at the University of Toronto’s Computational Social Science Lab.
- Maia-3 source code github.com/CSSLab/maia3, 1e13597
- The weights we run huggingface.co/UofTCSSLab/Maia3-5M, b6559de
- Our service code The exact code our server runs, served by us
- GNU AGPL, version 3 Full text, served by us. Also at gnu.org/licenses/agpl-3.0
The AGPL lets anyone use, study, share and change Maia-3, and asks everyone who runs a changed version for others to share the changes. Ours are all in the service and export script above. Maia-3 only ever sees positions, never who is playing.
Also part of every page
- Lichess chess openings The names, ECO codes and moves of every line in the opening encyclopedia. The Lichess contributors
- Lichess opening explorer Master and online statistics in the encyclopedia and the Titled Lab, asked through our server and kept for a month. lichess.org
- Lichess open database The online games behind the rating statistics in the opening encyclopedia. lichess.org
- Lichess broadcasts The games in the game database, from official tournament broadcasts. lichess.org
- FIDE rating lists The ratings on the leaderboard and player pages, read from FIDE’s monthly lists. FIDE
- Wikidata Some clubs in the club directory: name, town, website and founding year. The Wikidata contributors
- chess.js The rules of chess on the board: legal moves, check, mate and draws. Jeff Hlywa
- flag-icons Country flags next to players, federations and clubs. Panayiotis Lipiridis
- sharp Resizes profile photos and removes their camera and location data. Lovell Fuller and contributors
- libvips The image library behind sharp, linked as a shared library. John Cupitt and contributors
- Bricolage Grotesque The typeface for headings. The Bricolage Grotesque Project Authors
- Geist, Geist Mono The typefaces for text and numbers. The Geist Project Authors
- Noto Sans Devanagari The typeface for Hindi. The Noto Project Authors
- Svelte, SvelteKit The framework that builds every page. The Svelte contributors
- Classic A piece set you can choose under Board and pieces. Colin M.L. Burnett
- Merida A piece set you can choose under Board and pieces. Armando Hernandez Marroquin
- Chessnut A piece set you can choose under Board and pieces. Alexis Luengas
- Modern A piece set you can choose under Board and pieces. Maxime Chupin
- Papercut A piece set you can choose under Board and pieces. Nikolay Anzarov
- Toy A piece set you can choose under Board and pieces. RhosGFX
All of it is served from our own server. Nothing on this list phones home.