Enter your Chess.com username and BlackboxChess pulls your recent games automatically, then runs Stockfish across your last 10 to 100 of them. Instead of grading a single game, it finds the mistake patterns that show up again and again across your account. One bad game is noise. A pattern across 50 games is something worth fixing.
You give us your Chess.com username, and we fetch your recent games straight from your public archive. No exporting PGNs by hand. Stockfish then evaluates every position in every game and flags where you dropped significant material or missed a winning line. Those positions get grouped into recurring mistake patterns.
The patterns are ranked by how much each one costs you on average per game, not just how often it happens. A mistake that shows up twice a game and costs two pawns matters more than one that happens once a month.
BlackboxChess tracks a large library of mistake patterns, covering things like hanging pieces, back rank weaknesses, failing to convert winning positions, endgame technique, opening preparation gaps, and unfavorable trades. Each one maps to a different underlying problem in your play.
Most players have one category that is clearly worse than the rest. Across a full sweep of your Chess.com games, that weakness stops hiding behind individual results and becomes obvious. That is the one worth working on first.
Chess.com's own Game Review is good at showing you where you went wrong in one specific game. What it does not do is tell you which of your mistakes is structural, meaning the kind of thing that will show up again next game regardless of opening or opponent.
That is the gap here. BlackboxChess looks across your entire recent Chess.com history to find what you actually keep doing wrong, not what went wrong on move 23 of last night's blitz game.
The free tier analyzes your last 10 Chess.com games and shows your number-one mistake pattern. No account, no card required. The $10 full report covers 100 games, ranks every pattern by severity, includes three real game examples for each one with move-by-move context, and generates a short fix course built around your specific weakness. If the engine-verified analysis is factually wrong, you get a refund.
From a recent analysis
"Got my three weaknesses already: back rank blunders, unnecessary queen trades, losing my advantage."
Chess.com player, ~1200 Elo