Open-source licences
Last updated 31 August 2026
Chess Wizard is built on other people's work. Here is what, and under what terms.
Bundled and used
| Component | Licence | Used for |
|---|---|---|
| Stockfish 18 (lite, single-threaded WASM build) | GPL-3.0-or-later | The engine. Bundled with the extension. |
| chess.js 1.x | BSD-2-Clause | Move generation, legality checking, and PGN parsing. |
| Astro 5.x | MIT | Builds this website. |
| Cburnett chess pieces SVG diagram set | CC BY-SA 3.0 | Piece silhouettes on marketing board schematics, recolored. |
Stockfish and the GPL
Stockfish is licensed under the GNU General Public License, version 3 or later. The Chess Wizard extension distributes a WebAssembly build of Stockfish, which means:
- The full text of the GPL-3.0 is included with the extension.
- You are entitled to the complete corresponding source of the Stockfish build we ship. It is available from the upstream project, and we will provide our exact build inputs on request — ask.
- You are free to modify and redistribute Stockfish under the same terms. Nothing in our terms of service restricts the rights the GPL grants you.
Chess Wizard's own extension code is a separate work that communicates with the engine over the standard UCI protocol. The website and its backend are proprietary and are not covered by the GPL.
Something missing?
If we are using your work and it is not credited here, that is an oversight and we want to fix it. Tell us and we will correct the page.