Chessist

A Chromium extension that adds a live evaluation bar to Chess.com games, powered by Stockfish.
Created by lurimous

GitHub • Discord

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Screenshots

Features

• Real-time position evaluation displayed as a vertical bar
• Score shown in pawns format (e.g., +1.5)
• Works on live games, spectating, analysis, and archived games
• Optional best move display with arrow overlay
• Auto-move functionality
• Configurable engine depth (up to 50)
• Native Stockfish support for faster analysis
• Runs entirely in your browser (no server required)

Quick Start

1. Download the Extension

Download or clone this repository:

git clone https://github.com/lurimous/Chessist.git

2. Load the Extension

For Chrome/Brave/Edge:

1. Open your browser and go to chrome://extensions (or brave://extensions / edge://extensions)
2. Enable "Developer mode" (toggle in top right)
3. Click "Load unpacked"
4. Select the Chessist folder
5. The extension icon should appear in your toolbar

3. Play Chess!

1. Go to https://www.chess.com
2. Open any game (live, analysis, or archived)
3. You should see an evaluation bar on the left side of the board

That's it! The built-in WASM engine works out of the box.

Configuration

Click the extension icon to:

• Toggle the extension on/off
• See current evaluation
• Show/hide best move suggestion
• Enable auto-move
• Adjust engine analysis depth (10-50)
• Select playing color (Auto/White/Black)
• Switch between WASM and Native engine

Using Native Stockfish (Recommended)

For much faster analysis (10-100x), you can use a locally installed Stockfish.

Requirements

• Python 3 installed and in PATH
• Stockfish installed on your system

Setup

1. Install Stockfish

   • Download from https://stockfishchess.org/download/
   • Extract to C:\stockfish\ or add to PATH

2. Run the installer

   cd native-host
   install.bat
   

   Enter your extension ID when prompted (shown in the extension popup).

3. Select Native in extension

   • Click the extension icon
   • Click "Native" under Engine
   • Status should show "Connected: [path to stockfish]"

Benefits of Native

• Multi-threaded: Uses all CPU cores
• More memory: Larger hash tables
• Higher depth: Can analyze deeper (depth 50+)
• Faster: 10-100x faster than WASM

Project Structure

Chessist/
├── manifest.json           # Extension configuration
├── src/
│   ├── content/            # Injected into Chess.com pages
│   │   ├── content.js      # Board detection & eval bar
│   │   └── content.css     # Eval bar styling
│   ├── background/
│   │   └── service-worker.js
│   ├── engine/
│   │   ├── stockfish.js    # Stockfish WASM (included)
│   │   └── stockfish.wasm  # Stockfish binary (included)
│   ├── offscreen/          # Runs Stockfish engine
│   │   ├── offscreen.html
│   │   └── offscreen.js
│   ├── popup/              # Extension popup
│   │   ├── popup.html
│   │   ├── popup.js
│   │   └── popup.css
│   └── options/            # Settings page
│       ├── options.html
│       ├── options.js
│       └── options.css
├── native-host/            # Native Stockfish integration
│   ├── install.bat
│   ├── stockfish_host.py
│   └── manifest.json.template
└── icons/
    ├── icon16.png
    ├── icon48.png
    └── icon128.png

Troubleshooting

Eval bar doesn't appear:

• Make sure you're on chess.com (not another chess site)
• Try refreshing the page
• Check that the extension is enabled

Extension not loading:

• Check for errors in chrome://extensions
• Look at the service worker console for errors

"Extension context invalidated" error:

• This happens after playing many games when Chrome restarts the service worker
• Simply refresh the Chess.com page to restore functionality

Native engine not connecting:

• Run install.bat again with the correct extension ID
• Make sure Python 3 is installed and in PATH
• Check that Stockfish is installed and accessible

Credits

• Created by lurimous
• Powered by Stockfish
• WASM build from lichess-org/stockfish.js

License

MIT