What counts
Only engine-confirmed mistakes
The same browser-side Stockfish pipeline as Game Review evaluates the position before and after every move. A winning-chance loss of at least 10 points is a mistake; at least 20 is a blunder. Good moves are not turned into artificial exercises.
FAQ
Training from your own games
How are personal blunder puzzles created?
Stockfish analyzes every main-line position in your PGN at depth 18. Chessdesk creates a puzzle only when the review classifies your move as a mistake or blunder and verifies the engine's better move as legal.
Is my PGN uploaded?
No. The PGN and Stockfish analysis stay in your browser. This free tool does not save the game unless you later choose to put work into your Chessdesk account.
Why did my game produce no puzzles?
The engine may not have found a winning-chance loss large enough to classify as a mistake or blunder at depth 18. The tool does not create filler puzzles from good moves.
How long can the submitted game be?
The browser tool accepts one game of up to 150 half-moves. Longer games take too long to analyze position by position, so use Game Review directly for a different workflow.
Keep the lesson, not just the answer
Review the entire game, save critical positions in a Study, or create an account to keep your coaching work together.