A blunder is a seriously bad chess move — one that throws away material, a winning position, or the whole game. In notation it gets the harshest mark of all: a double question mark, ??, written right after the move.
Blunders are the drama of chess. They flip decided games, snatch defeat from certain victory, and — crucially — happen to everyone. Beginners hang pieces; grandmasters miss a one-move threat in time trouble. Nobody is immune, which is oddly comforting.
Blunder vs. mistake vs. inaccuracy
Not every bad move is a blunder. Chess annotators (and the “game review” tools on Chess.com and Lichess) grade errors on a sliding scale:
| Symbol | Name | Roughly means |
|---|---|---|
| ?! | Inaccuracy / dubious move | Slightly off — a better move existed |
| ? | Mistake | A clear error that hands over an edge |
| ?? | Blunder | A game-changing error — dropping a piece, missing mate, or hanging your queen |
A quick illustration of the idea: imagine you’re comfortably ahead, your opponent offers a queen trade, and you recapture with the wrong piece — suddenly your king is exposed and the game collapses. That single move is the blunder; everything before it was fine.
The good news: most blunders come from not looking, not from lack of skill. A simple pre-move habit — “is anything of mine hanging? what does this move let my opponent do?” — prevents the vast majority of them.
Related terms
- Fix yours: how to stop blundering — a practical habit that works
- Common beginner mistakes — the blunders everyone makes first
- Brilliant move — the flip side, marked !!
- Level up at the improvement hub
- Back to the chess glossary
Frequently asked questions
What symbol marks a blunder? A double question mark, ??, placed after the move — for example, “24.Qxh7??”.
What’s the difference between a blunder and a mistake? A mistake (?) hands your opponent an advantage; a blunder (??) is worse — it typically loses material or the game outright.
Do grandmasters blunder? Yes, regularly — especially in fast time controls or time trouble. Blundering less, not never, is the mark of a strong player.
Written and fact-checked by the Chess Lab Academy Editorial Team (AI-assisted, human-edited) · Definitions checked against Wikipedia’s Glossary of chess · Last verified 2026-07-13 · Sources · How we verify content.