How is a brilliant (!!) move determined?

Most review sites don't explain why they call a move "brilliant". We publish our rule as it is: a move is Brilliant (!!) when all of the conditions below hold.

The rule

1. It must be the engine's best move. If it is not the best move Stockfish found in that position, it is not brilliant.
2. A piece must be sacrificed. The moving piece must not be a pawn or the king. Its value must be at least 2 points more than the piece it captured on that move (pawn 1, knight 3, bishop 3, rook 5, queen 9). In other words, the piece is put en prise without getting its value back.
3. The opponent must be able to take it. The opponent must have a capture on the square the piece moved to, and one of these must be true:
   • the opponent can take it with a cheaper piece, or
   • if the opponent takes it with an equal or more valuable piece, we cannot recapture on that square.
4. The sacrifice must be sound: after the move, the evaluation must stay better than −1 pawn for the player who made it. Giving away a piece badly is not brilliant.
5. The game must not already be decided: before the move, the player must not be more than +5 pawns ahead. Giving up a piece in an easily won game is not brilliant.

Limits of the rule

The rule is deliberately simple; it does not catch:

• Pawn sacrifices (as in gambits). Only knights, bishops, rooks and queens count.
• Pieces left hanging elsewhere. It only looks at the square the piece moved to; a piece that becomes undefended somewhere else because of the move (for example via an opened line) is not seen as a sacrifice.
• Deep exchanges: it only checks the opponent's first capture and whether we can recapture.

So some real sacrifices may only show up as "Best". Conversely, a move that meets the conditions but looks quite ordinary to a human can occasionally be marked Brilliant.

Is it the same as Chess.com?

No. We don't know Chess.com's exact method (its thresholds and engine settings), so we can't claim to give identical results. In the same game, a move Chess.com calls "Brilliant" may get a different class from us, or the other way around. How the other classes are calculated is on this page.