How to stop blundering in chess: train the blunder check
A blunder is rarely a deep miscalculation. In hundreds of online games at every level checked by Stockfish, four in five costly mistakes were punished by a capture, a check or a simple threat, and nearly half by a plain capture. The move that loses is usually the one you didn't check.
The blunder check is the habit that catches them: before you play a move, look at it from your opponent's side. What can they capture? What checks do they have? What does your move stop defending? OptiChess trains that habit directly.
How the exercise works
You're shown a position and a move, and asked: "If you play this move, can your opponent gain anything?" Either the move is safe, and you answer No, or you pick the reply that punishes it.
The pawn on e5 looks free, but the answer is Yes: 4...Qg5! The queen attacks the knight on e5 and the pawn on g2 at the same time. Taking more with 5.Nxf7 loses to 5...Qxg2 6.Rf1 Qxe4+ 7.Be2 Nf3 mate, so White loses the knight for one or two pawns. Safe was simply 4.Nxd4 or castling.
Half the positions are safe and half are not, served in turn, so you can't guess the answer from the level: you have to look.
What you'll meet at each level
- Around 800: a piece left to a one-move capture.
- 1200 to 1600: the blunders players at that level commonly make, such as a capture that loses to a fork, or a king walking into a check.
- 1800 and up: blunders strong players made in their own games.
Where the positions come from
Every position is from a real game, and the blunders are the ones players actually make: a position's rating comes from how often players at each level play the losing move. Every reply offered is played out by the engine, and the explanation plays out the line, so you see why it loses, not just that it does.
Train it with the rest
Blunder checks are one of nine kinds of question in OptiChess, mixed with tactics, endgames and positional judgement. With your Lichess or Chess.com games connected, you also get blunder checks from your own games: the moves you actually played.
Try it. Real positions, set at your level, every answer checked against the board. No account needed to start.
Start training