Chess Move Classifications, Explained
A game review labels every move with one of ten classifications, from Brilliant (!!) to Blunder (??).
Each label is based on how much winning chance (win probability) a move gives up — not the raw engine score. That’s why the same centipawn loss can be a “mistake” in a tense position and barely an “inaccuracy” in a decided one. You can see all ten on your own games in the free game review.
The ten move classifications
- Brilliant (!!) — a sound sacrifice: you give up material yet the move is still best (or near-best) and keeps you in good shape.
- Great — the only good move in a sharp position; the alternatives would have thrown much of the advantage away.
- Best — the engine’s top choice.
- Excellent — a near-best move that gives up only a sliver of win probability.
- Good — a solid move that keeps your position, a little behind the engine’s pick.
- Book — a known opening-theory move, named from the opening book.
- Inaccuracy (?!) — a slightly imprecise move that loses a small part of your advantage.
- Mistake (?) — a clear error that meaningfully worsens your position.
- Miss — failing to punish the opponent’s error, or letting a forced mate slip.
- Blunder (??) — a serious error that loses material or allows a mate.
Blunder vs. mistake vs. inaccuracy
These three sit on a spectrum of how much you gave up. An inaccuracy costs a little; a mistake costs a clear amount; a blunder costs a lot and loses material or allows mate. That last gate matters: in a completely winning position, a move that only a computer would refute is kept as a mistake, not flagged as a blunder — the same recalibration chess.com made so that engine-only “blunders” stop being scary.
How the labels are decided
Every position is evaluated by Stockfish, the eval is converted to a win percentage, and the win% you lost on the move drives the label. A big centipawn loss escalates the result so decided positions don’t hide real errors. On top of that, special detectors catch sacrifices (Brilliant), only-moves (Great), and failures to punish (Miss). The full method is in the About page and the open formulas it links to.
Frequently asked questions
What’s the difference between a blunder and a mistake?
Both are errors, but a blunder is worse: it’s a serious drop in winning chances that also loses material or allows a forced mate. A mistake clearly worsens your position but doesn’t hang material or walk into mate. In a totally winning position, a move that only the engine would punish is kept as a mistake rather than a blunder.
What makes a move ‘brilliant’?
A brilliant move (!!) is a sound sacrifice: you give up material, the piece is genuinely en prise, and yet the move is still the best (or near-best) and keeps you in good shape. If giving up the material were simply losing, it wouldn’t be brilliant.
Why was my move ‘good’ and not ‘best’?
‘Best’ is the engine’s single top choice. ‘Excellent’ and ‘Good’ are near-best moves that keep your position — they give up only a tiny amount of win probability, so they’re fine, just not the engine’s first pick.
What is a ‘miss’?
A miss is failing to punish: your opponent just blundered (or you had a forced mate) and you didn’t take the chance, giving back a meaningful slice of your advantage.
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