Chess blunder checker
Paste a game and GameLens flags every blunder, mistake, and missed win — each with a plain-English explanation of what went wrong: the fork you allowed, the piece you left hanging, the back-rank mate you walked into.
Unlike raw engine output, you don't need to read centipawn evaluations. Every flagged move tells you what happened and what you should have seen.
Nothing is uploaded — analysis runs locally on your device.
What gets flagged
- • Blunders — moves that swing the game by 10%+ winning chances
- • Mistakes — clear losses of advantage (5–10%)
- • Inaccuracies — small slips that let pressure build
- • Missed wins — tactics you had but didn't play
- • Best moves — so you see what good looked like in the same position