Opening Leak Lab

Bird Opening

A02 1. f4

Black scores 45.7% here across 1,195 club games — but the 5.9% who answer Nc6 score 34.3%, 11 points worse.

What Black actually plays here

Across 1,195 games from a Lichess-derived book of club play, Black scores 45.7% in this position. These are the replies people choose, and how each one works out.

ReplyGamesShare Black scoresVerdict
d5 517 43.3% 43.6% holds up
e6 176 14.7% 44.9% holds up
e5 99 8.3% 59.6% holds up
c5 84 7.0% 51.2% holds up
Nf6 78 6.5% 50.0% holds up
Nc6 70 5.9% 34.3% below the line
b6 39 3.3% 41.0% below the line
f5 38 3.2% 34.2% below the line
d6 33 2.8% 48.5% holds up
g6 31 2.6% 54.8% 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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