London System
A48 1. d4 Nf6 2. Nf3 g6 3. Bf4 Bg7 4. e3 d6
Black scores 53.6% here across 522 club games — but the 56.5% who answer O-O score 49.8%, 4 points worse.
What Black actually plays here
Across 522 games from a Lichess-derived book of club play, Black scores 53.6% in this position. These are the replies people choose, and how each one works out.
| Reply | Games | Share | Black scores | Verdict |
|---|---|---|---|---|
| O-O | 295 | 56.5% | 49.8% | below the line |
| d6 | 165 | 31.6% | 60.3% | holds up |
| d5 | 27 | 5.2% | 48.1% | below the line |
"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.