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    Free Chess Game Analysis

    Free tool · No account needed

    Anderssen – Kieseritzky · London 1851

    Example
    After 20… Na6: ??Blunder

    Evaluation

    Accuracy

    White
    90.8
    Black
    84.8
    • ?!Inaccuracy1
    • ?Mistake2
    • ??Blunder1

    Where the game turned

    1. 16… Bc5?!Inaccuracy32% → 21%

      Bc5 made a difficult position worse; Qc6 put up more resistance.

    2. 18. Bd6?Mistake71% → 50%

      Bd6 left the rook on a1 to be taken: Qxa1+.

    3. 20… Na6??Blunder36% → 0%

      Na6 allowed a forced mate, starting with Nxg7+. Ba6 was the move.

    Example: the Immortal Game (Anderssen–Kieseritzky, 1851), reviewed by Stockfish 18 running in the browser. Your own game gets the same review.

    Runs in your browser. Nothing is uploaded.

    Load a PGN and Stockfish runs in this tab, not on a server. Switch the engine on, analyze the whole game, and the move list fills with the verdict on each move: an accuracy figure per side, and a mark against every inaccuracy, mistake and blunder. Step through any position to see the engine’s lines and the move it preferred.

    How to analyze a game

    1. 1.

      Paste the PGN into the box, or open a .pgn file. The example game loads with one tap if you just want to see how it works.

    2. 2.

      Flip the Turn on the engine switch. The engine is about seven megabytes and is fetched once, so the first run takes a moment.

    3. 3.

      Press Analyze the whole game. Progress runs along the move list as each position is searched.

    4. 4.

      Tap any move to see its verdict, the engine’s preferred move, and the lines from that position.

    What this tool does

    The engine runs on your device

    Stockfish 18 is downloaded once and searches in your browser. Your games are never sent anywhere, and there is no queue and no daily limit.

    A verdict on every move

    The whole-game analysis walks each position and scores the move that was played against the one the engine wanted, in winning chances rather than raw centipawns.

    Accuracy for both sides

    Each side gets a single accuracy figure, plus counts of inaccuracies, mistakes and blunders, so a post-mortem has somewhere to start.

    Lines you can walk into

    Any variation the engine suggests can be played out on the board and stepped through move by move, then dropped to return to the game.

    Frequently asked questions

    Is the analysis really free, with no account?

    Yes. The engine runs in your browser, so there is nothing to meter. No sign-up, no credits, no daily cap on how many games you analyze.

    Does my game get uploaded?

    No. The PGN is parsed in the page and the engine searches on your own processor. Nothing about the game leaves your device.

    Why is the first analysis slow?

    The WebAssembly engine has to be downloaded before it can search. After that it is cached, and later visits start immediately.

    How do I analyze a game I played on paper?

    Photograph the scoresheet and run it through the ScanChess scanner first. It reads the handwriting, checks every move against the rules and gives you a PGN you can paste straight in here.

    Which engine is this, and how strong is the analysis?

    Stockfish 18, the lite single-threaded WebAssembly build. The whole-game analysis gives every position the same fixed amount of search from a clean start, so the same game always gets the same marks, and every move about to be marked a mistake or blunder is searched again, deeper, before the mark is shown. Stepping to a single position searches it deeper still. For serious opening preparation a desktop engine given minutes per move will always see further.

    What do the accuracy numbers mean?

    Each move is scored by how much winning chance it gave away compared with the engine’s choice, and the accuracy figure is the average across a side’s moves. It is a summary, not a rating: a quiet game with few decisions will score higher than a sharp one played just as well.

    How is this different from Chess.com Game Review or Lichess analysis?

    Chess.com limits how many full Game Reviews a free account can run, and Lichess analyzes a game once it has been imported into the site. This tool needs neither an account nor an import: paste any PGN, including one scanned from a paper scoresheet, and Stockfish reviews it in your browser with no daily limit.

    Is the game on a paper scoresheet? Scan it into PGN instead of typing it.

    Scan an imageTry the free example

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    Guides for this tool

    The game you want to analyze is on paper

    ScanChess reads a photographed scoresheet into a validated PGN, ready to analyze. New accounts start with free credits.

    Scan a scoresheet