Open-Source Licenses

Stockfish — GPL-3.0

BlunderLoop's analysis is powered by the Stockfish chess engine, which is free software licensed under the GNU General Public License version 3.

• Source code: github.com/official-stockfish/Stockfish — the complete corresponding source of the engine.
• Distribution on this site: we serve a WebAssembly build of Stockfish (Stockfish 18 Lite, single-threaded) from /engine/ so analysis can run entirely in your browser. That build is distributed under the same GPL-3.0 terms; the full license text ships alongside it at /engine/COPYING.txt.

Lichess data — CC0 1.0

Opening and puzzle reference data derived from the Lichess open database is dedicated to the public domain under CC0 1.0 Universal. Thank you, Lichess.

npm dependencies

The application itself is built on open-source packages, including:

• Next.js and React — MIT License
• chess.js — BSD 2-Clause License
• react-chessboard — MIT License
• @supabase/supabase-js — MIT License
• stockfish (npm packaging of the WASM build) — GPL-3.0

Each package's full license text is included in its published package. Development tooling (TypeScript, ESLint, Vitest, Playwright, Testing Library) is likewise open source under MIT or similarly permissive licenses.

BlunderLoop itself

BlunderLoop is open source. Because it distributes and links a GPL-3.0 engine build, the engine components remain under GPL-3.0, and the pointers above are the canonical way to obtain their source.