Credits and licenses

We write the games and draw the graphics on vladier ourselves. A few parts come from open source projects and open data, listed here with their licenses. Thank you to everyone who builds and shares them.

Stockfish

Chess engine on the Play Chess Against the Computer page. License: GNU General Public License v3. Source: github.com/official-stockfish/Stockfish. Runs unmodified in your browser as WebAssembly. Version 19 (stockfish.js lite single-threaded build by Nathan Rugg). Source code of the browser build: https://github.com/nmrugg/stockfish.js. License text: /engine/COPYING.txt

chess.js

Chess move rules on the chess pages. License: BSD 2-Clause. Source: github.com/jhlywa/chess.js.

Chess pieces by Colin M.L. Burnett

Chess piece images on the chess pages. License: BSD 3-Clause (one of the licenses offered by the author). Source: commons.wikimedia.org/wiki/Category:SVG_chess_pieces. Reformatted only (file names and viewBox).

Lichess puzzle database

Positions on the Chess Puzzles page. License: Creative Commons CC0 (public domain). Source: database.lichess.org/#puzzles. A curated selection. Thank you to lichess.org and its players.

Archivo, Source Sans 3, Unbounded

Fonts. License: SIL Open Font License 1.1. Source: fonts.google.com.

Game names

Sudoku, checkers, spider solitaire, FreeCell, minesweeper and the other games on this site are traditional games known by generic names. Our versions are original implementations and are not affiliated with any company that sells its own edition.