Running Stockfish on one game tells you where you blundered. Running it across 100 games tells you which type of mistake you keep making. That's the difference. BlackboxChess does the bulk run, classifies your errors, and ranks them by how much they actually cost you.
Stockfish runs at depth 8 across each of your games. At every move, it calculates the best continuation and compares it to what you played. Positions where the evaluation dropped significantly get flagged.
Those flagged positions are then classified into recurring mistake types rather than labeled generically as blunders or inaccuracies. The classification tracks what kind of mistake it was across categories including material loss, king safety, piece activity, pawn structure, and endgame technique.
Depth 8 is fast enough to run across a large batch of games without making you wait an hour for results. For identifying recurring mistake patterns in club-level and intermediate play, depth 8 is sufficient. The mistakes it catches are real.
If the engine identifies a pattern that seems wrong for your games, contact support. Factually incorrect analysis is grounds for a refund.
Both platforms have Stockfish integration for individual game review. That's useful for understanding specific games. What they don't do is aggregate findings across dozens of games and surface structural patterns.
BlackboxChess automates the bulk scan and produces a ranked summary. You don't have to manually review 30 games and try to spot the trend yourself. The engine does the scanning; the output is the diagnosis.
Lichess connects via OAuth in one click. Chess.com uses a quick verification challenge, you paste a short code into your Chess.com Location field, we verify it, then you remove it. You can also upload a PGN file directly. The free tier covers 10 games; the $10 full report covers 100.
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Lichess player, ~1450 Elo