Common opening mistakes at 1800–1999 Elo — and how to punish them

51% of Lichess players rated 1800–1999 who reach the Vienna Gambit make a mistake or blunder on the lines we teach within the first 10 moves (1.4M games, a lower bound). That is the top of this page’s ranking; the table lists every opening we teach in the same order, with the slip that costs the most and the answer to it.

These are Lichess ratings — Lichess uses the Glicko-2 system, though most players say Elo — for blitz, rapid and classical games. Chess.com ratings run a few hundred points lower at club level, so this band corresponds to ≈1500–1750 on Chess.com.

For each opening, the counted mistake that adds most to its number: how often it is played at this level, weighted by how often the position is reached. Each is graded against Stockfish at depth 20 with the game review’s own labels; the close calls were re-graded at depth 30. “Their better move” is the engine’s choice for them; “the answer” is the line we teach against the slip.

Only replies we have listed and graded can count, so a rare reply that never made the table adds nothing even when it is a mistake. A band prints a number only when at least 1.0K games reached the opening and at least 80% of the on-line traffic is graded.