ChessAnalysis

ChessAnalysis is a browser‑based chess review tool that lets you import games from Chess.com, Lichess, or paste a PGN. The site runs Stockfish 19 locally, so the analysis is private and unlimited. After loading a game, you get a report that shows accuracy for both players, highlights every blunder, mistake, and inaccuracy, and explains the three biggest mistakes. The short explanations suggest the move you should have played and what the line would have been. You can replay each mistake on the board, download an annotated PGN, or share a link to the review.

The workflow is simple. First, type a Chess.com or Lichess username to pull your most recent game, or paste any PGN string. Stockfish evaluates every move on the client side; most games finish in seconds. Third, look at the accuracy strip that shows how many percentage points of winning chance were lost or gained by each move. An inaccuracy is marked with “?.” when it costs 5 % or more, a mistake with “?” for 10 % or more, and a blunder with “??” for 15 % or more. The evaluation graph lets you click on a sharp drop to jump to that position and see who was winning before and after the move. For every key mistake the site displays a deeper analysis, a suggested best move, and a concise explanation of why the original move was costly.

The tool also includes a free online chess board, a live engine line feature, a next‑move calculator, a board editor, an online chess clock with increment, a FIDE Elo calculator, and a board‑setup guide. These add‑ons are useful for practice, but they do not replace the main analysis workflow. The site does not publish pricing or tiered plans; all features listed are available for free.

Key features

• Import games by Chess.com or Lichess username or paste a PGN
• Stockfish 19 runs locally, ensuring unlimited, private reviews
• Accuracy scores for both sides using the open Lichess formula
• Explicit grading: inaccuracy (?.), mistake (?), blunder (??) with winning‑chance thresholds
• Evaluation graph with clickable moments and a clear who‑is‑winning view
• Three key mistake explanations, each with the best move and a short line
• Replay of key mistakes on an interactive board
• Download annotated PGN or share a review link