Chesscomputer

Free the fish! Analyze your chess.com and Lichess games with Stockfish -- for free, right in a side panel.

chess.com.puter brings the power of Stockfish 18 to your browser without paying for a premium subscription. Open any completed game on chess.com or Lichess, click Import, and get a full game analysis in seconds. Or paste any PGN. Or open the Sandbox and explore from a fresh board.

FEATURES

Works on Chess.com and Lichess
Import completed games from either site with one click. The extension automatically detects games on the current page.

Full Game Analysis
Every position evaluated by Stockfish 18 running locally in your browser. No server. No cloud. No waiting in a queue. Your computer does the work.

Move Classifications
See exactly where you went wrong (and right). Moves are classified using the Expected Points model: Best, Excellent, Good, Book, Inaccuracy, Mistake, and Blunder -- with colored annotations and icons on the board.

Accuracy Score
Your overall accuracy percentage, calculated using the same formula as Lichess.

Interactive Board
Click any move to jump to that position. Drag pieces to explore "what if" lines -- hypothetical variations appear inline in the move list.

Evaluation Chart
A smoothed win-probability graph over the entire game. Click anywhere on the chart to jump to that moment. Mistakes and blunders are marked with colored dots.

Multi-PV Engine Lines
See the top 1-5 engine lines updating in real-time as Stockfish searches deeper. Click any line to play it out as a hypothetical variation. Adjust depth and number of lines with simple controls.

Best Move Arrows
Semi-transparent arrows on the board show what the engine recommends.

Player-Focused
Summary stats, accuracy, and move coloring focus on your moves. Flip the board to see your opponent's perspective.

Paste PGN
Paste any completed game in PGN format to analyze it -- no need to be on a chess site.

Sandbox
Open a fresh starting position and freely explore with full engine analysis. No PGN required.

Live Helper
During active games, the extension shows mirrored clocks with time-difference indicators and low-time alerts. Stockfish analysis is disabled -- but the clocks help you manage your time. When the game ends, analysis becomes available automatically.

Open in Lichess
One click to continue analysis on lichess.org's full analysis board.

ANTI-CHEATING

Stockfish analysis is strictly disabled during active games -- three independent checks enforce this. Imported and pasted games must be completed before analysis runs. Games are never auto-imported; you always choose when to analyze. Sandbox mode is the only way to use the engine freely, and it is not connected to any live game.

PRIVACY

Zero network calls at runtime. No APIs. No tracking. No data collection. Everything runs locally on your machine. The source code is open and auditable.

TECHNICAL DETAILS

Built with Lichess open-source tools: chessground (board UI), chessops (chess logic), and Stockfish 18 WebAssembly. Vanilla JavaScript -- no frameworks. ~15 MB total (mostly the Stockfish neural network).

FREE & OPEN SOURCE

Licensed under GPL-3.0. Free as in freedom, free as in beer. Free the fish!

https://github.com/reynoldsnlp/chess.com.puter

DISCLAIMER

Chess.com is a registered trademark of Chess.com, LLC. This extension is an independent, open-source project and is not affiliated with, endorsed by, or sponsored by Chess.com, LLC. Lichess is a registered trademark of Lichess.org. This extension is not affiliated with or endorsed by Lichess.org.