Kibitz

A Chrome/Edge (Manifest V3) extension that overlays live Stockfish analysis on chess.com — like a kibitzer leaning over your shoulder and pointing at the board.

Features

• Best-move arrows — the top engine moves drawn on the board on your turn.
• Evaluation bar — a live who's-winning bar at the edge of the board, updated every position.
• Blunder colors — click one of your pieces and its legal destination squares are colored green → yellow → orange → red by how much evaluation each move loses versus the best move.

Master on/off toggle in the popup, or press Alt+C on a chess.com tab.

Install (unpacked)

1. npm install
2. npm run build
3. Chrome/Edge → chrome://extensions → enable Developer mode → Load unpacked → select the dist/ folder.
4. Click the Kibitz toolbar icon → toggle ON (or press Alt+C on a chess.com tab).

Development

• npm test — unit tests (Vitest).
• npm run build — production build to dist/.
• npm run dev — watch build.

Stack: TypeScript, Vite + CRXJS (MV3), chess.js, Stockfish (WASM), Vitest.

Engine & license

Kibitz bundles Stockfish (a single-threaded NNUE WebAssembly build) to do the analysis. Stockfish is licensed under the GNU General Public License v3.0. Because Kibitz distributes Stockfish as part of the extension, the project as a whole is distributed under GPL-3.0-or-later — see LICENSE and public/engine/README.md for engine attribution and the corresponding source.