Opening Leak Lab

Center Game: Kieseritzky Variation

C21 1. e4 e5 2. d4 exd4 3. Nf3 c5 4. Bc4

Black scores 46.8% here across 970 club games — but the 16.9% who answer c5 score 40.2%, 7 points worse.

What Black actually plays here

Across 970 games from a Lichess-derived book of club play, Black scores 46.8% in this position. These are the replies people choose, and how each one works out.

ReplyGamesShare Black scoresVerdict
Nc6 483 49.8% 45.4% holds up
c5 164 16.9% 40.2% below the line
Bc5 71 7.3% 59.2% holds up
Nf6 71 7.3% 49.3% holds up
d6 54 5.6% 43.5% below the line
d5 52 5.4% 56.7% holds up
Bb4+ 35 3.6% 48.6% holds up

"Below the line" means the reply scores at least three points worse than the position does overall. Replies played fewer than 25 times are left out: the sample is too small to read.

Is this costing you anything?

A table of averages cannot tell you whether you go wrong here — only your own games can. Opening Leak Lab reads your Chess.com or Lichess archive, finds the decisions you repeat, and checks each one against this book and a bundled Stockfish.

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