Free tool
Chess game analyzer
Analyze a single game move by move with Stockfish, or point it at your username and analyze every game you have ever played at once. One game tells you what went wrong on Tuesday; your whole history tells you what to actually work on. Free, in your browser, no account.
Try the board first
This is the real analysis board with Stockfish running in your browser - find the move that was missed in an actual game.
What the analysis surfaces
A single-game engine board answers “what was best here?” A history analyzer answers “what do I keep getting wrong?” Audit Chess does both:
Every mistake, labelled
Inaccuracies, mistakes and blunders flagged by the size of the win-probability swing, not a raw pawn count - so the moves that actually changed the game stand out.
Game review →Openings ranked by result
Across your history, every opening you reach becomes a tree ranked by your real win/draw/loss record, so the lines quietly costing you points are obvious.
Opening tree →The wins you threw away
Games where you were winning by +3 and lost anyway, bucketed by whether it slipped in the opening, middlegame or endgame.
Blown wins →Puzzles from your blunders
Each real blunder becomes a Stockfish-verified puzzle that drops you back into the exact position you got wrong, so analysis turns into practice.
Blunder puzzles →One game, or all of them
Reviewing one game is the right move when you want to understand a specific loss - paste the PGN into the free analysis tool and walk the eval graph move by move. But a single game is a small sample. The reason you keep losing the same way is only visible across many games, which is why the whole-history analyzer is where most of the value is.
Prefer a narrower cut? Analyze just your openings, just your blunders, or profile another player with the player analyzer.
Analysis is only useful if it changes your training
A list of engine evaluations is not a study plan. The point of analyzing your games is to decide what to drill next, so Audit Chess ends where most analyzers stop: it ranks your openings by result, surfaces the mistakes you repeat, and turns your own blunders into puzzles you can practise. For the full method, read how to analyze your chess games, or compare tools in the best free chess game analyzers.
Who is it for?
Improving players
Stop guessing what to work on. See which openings and mistakes actually cost you rating, ranked by their real impact across your games.
Competitive players
Prep with your own results and scout opponents from their public games before a rated game or match.
Coaches
Point it at any student’s Chess.com or Lichess username to see their recurring patterns in minutes instead of clicking through games one by one.
Chess enthusiasts
Understand your own chess for free - no account, no install, nothing uploaded.
What is Audit Chess?
Audit Chess is a chess analysis platform that reads your Chess.com or Lichess game history and identifies the recurring weaknesses, opening tendencies, blunders, blown wins, missed mates and endgame patterns that are hard to see from a single game. It runs Stockfish in your browser, needs no account, and never uploads your games.
What makes it different: most chess engines analyze one position or one game. Audit Chess focuses on the patterns across your whole history - and turns them into training, so your own blunders become Stockfish-verified puzzles and your weakest openings become concrete things to study.
Frequently asked questions
How do I analyze a chess game?+
For a single game, paste its PGN into the free analysis tool and Audit Chess replays it move by move with Stockfish, marking every inaccuracy, mistake and blunder and drawing the evaluation graph. To analyze all your games at once, enter your Lichess or Chess.com username and it reviews your whole history and ranks where you actually lose points.
Do I need to upload a PGN file?+
No. You can paste PGN text for one game, or skip files entirely and enter a username - Audit Chess reads your public games straight from the Lichess and Chess.com APIs. Nothing is uploaded to a server either way; the engine runs in your browser.
What engine does it use, and how deep?+
It runs Stockfish compiled to WebAssembly, locally in your browser. The whole-history pass scores every move at depth 8 so it can cover hundreds of games quickly; single-game review and puzzle checking then run deeper on demand, around depth 14, position by position.
Is it really free?+
Yes - free, no account, no install. Because the analysis happens on your own device there is no server cost to pass on and nothing about your games leaves your machine.
Audit Chess is free and not affiliated with Chess.com or Lichess.