Drag pieces from the tray onto the board, then drag them again to any square — or off the board to take them off. Paste a FEN to jump straight to a position from a book, a puzzle, or a game you are replaying. Switch to Play when you want both sides to move under the rules, with Stockfish evaluating as you go.
Stockfish 18 re-evaluates after every move and draws its top choices on the board as arrows. The evaluation bar tracks who stands better, and depth is yours to set — quick for a rough read, deep when the position is sharp.
The engine is compiled to WebAssembly and runs inside your browser tab, so positions do not reach a server unless you explicitly enable de-identified game contribution. That is also why there is no account, no daily limit, and no charge for the analysis.
The board is for one position at a time. To have every move of a game scored and labelled instead, run a full game review — import a PGN, a Chess.com or Lichess link, and you get accuracy, blunders and the moment it turned.
