Chess Spectator Engine

Local Stockfish analysis for games you spectate on Lichess and Chess.com. Blocked while you are playing.

Analyze chess games you are watching with a fast, completely local engine. Chess Spectator Engine adds optional Stockfish analysis to supported Lichess and Chess.com spectator pages. See the evaluation from White's perspective, the best move, principal variations, a board evaluation bar, and a clear best-move arrow without sending the position to a cloud engine. Key features: - Stockfish 18 analysis for standard chess - Fairy-Stockfish support for compatible chess variants - One to five principal variations - Adjustable analysis depth - Best-move arrow and board evaluation bar - Movable, collapsible panel or a full-width horizontal top bar - Settings remembered across sessions - No account, API key, analytics, advertising, or developer server Spectator only: analysis is automatically blocked when the extension detects that you are a player in an active game. This extension is intended for watching completed or third-party games and for learning from those positions. Do not use engine assistance while playing. Privacy: the extension reads visible board data and player names on supported game pages only. Analysis happens on your device. Board positions, moves, names, and engine results are not sent to the developer or any third party. Permissions are limited to the two supported chess sites, extension settings storage, and the Manifest V3 offscreen document required to run the packaged Stockfish workers. Chess Spectator Engine is an independent project and is not affiliated with, endorsed by, or sponsored by Lichess or Chess.com.