Import a game or set up any position, and Stockfish analyzes every move in your browser. You get the evaluation, the best moves as arrows on the board and a report of every mistake. It's free, with nothing to install and no account needed.
Analyze a gameStockfish scores every position as you move the pieces or step through a game, with its best lines beside the board.
Swings towards whichever side is better, so you see the balance at a glance without reading a number.
The engine's top choices drawn on the board, colored from green for the best through yellow and orange to red for the weakest.
An accuracy score for each player, brilliant moves marked in teal, and every inaccuracy, mistake and blunder for both sides.
Every legal move evaluated at once, so you can compare all your options side by side.
Pick a piece and the engine scores it on every square, so you can see where a misplaced piece wants to go.
In the Quiz panel, guess the engine's choice and find out straight away whether you would have found it.
Build any position by hand, with who is to move, castling rights and en passant, then analyze it.
In the analysis panel, paste a game's link from Chess.com or Lichess, its PGN, or a FEN for a single position, or pick one of your recent games by username. The game opens on the board with the engine running. Step through it with the arrow keys, and the Report panel marks the moves that decided it. To try it on a famous game, open Morphy's Opera Game (Paris, 1858).
The game report compares every move with the engine's choice and grades it as a best move, a good one, an inaccuracy, a mistake or a blunder. It grades both players, so you see the chances your opponent gave you as well as the ones you gave away. Each player gets an accuracy score out of 100, and piece sacrifices that hold up are marked as brilliant moves. Click a count, such as White's blunders, to jump to the next of those moves with the engine running and see what was better.
What to look for in your own games:
Stockfish runs locally, in the browser tab, using WebAssembly. Nothing waits in a queue on a shared server, and you can review as many games as you like. The free engine uses one CPU core, which is plenty for checking a club game, and a subscription unlocks multi-threaded builds that use several cores at once.
That also means it works the same on a phone, and on a work laptop where you cannot install software.
In the analysis panel, paste the game's link from Chess.com or Lichess or its PGN, or find it in your recent games by username. Then open the Report panel: Stockfish analyzes the game in your browser and marks every inaccuracy, mistake and blunder for both sides. It's free and needs no account.
Yes. The board, the engine, the game report and the puzzles are free to use with no account. A paid tier adds faster, multi-threaded engines, but nothing on this page needs it.
No. Open the board and start analyzing. An account is only useful if you want your games saved across devices.
Stockfish, the strongest open-source chess engine, compiled to WebAssembly and running inside your browser rather than on a server.
Yes. In the analysis panel, paste the game's link from Chess.com or Lichess or its PGN, or find it in your recent games by username. The game opens on the board with the engine running, and the Report panel grades every move.
Yes. Paste a FEN into the analysis panel, or set the position up on the board editor, and the engine evaluates it straight away.
Yes. The eval bar sits beside the board and moves with the position, alongside the score and the engine's best lines. It works in the board editor too, so you can see how a position is judged while you set it up.
Yes. Each player gets an accuracy score from 0 to 100. Piece sacrifices that hold up are marked brilliant, alongside the best moves, inaccuracies, mistakes and blunders, and you can review as many games as you like.
A move that loses far more than the best move would have. The loss is weighed by the position: the same drop in evaluation counts for less when one side is already winning by a lot. Inaccuracies and mistakes are smaller losses on the same scale.