Castling

Castling is a special move that moves two pieces at once: the king moves two squares toward a rook, and the rook jumps over the king to the square next to it. It tucks the king into a safer corner and brings the rook toward the center.

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There are two kinds:

• Kingside castling, or castling short, written O-O.
• Queenside castling, or castling long, written O-O-O. The rook travels three squares.

Castling rules

1. Neither the king nor that rook has moved yet.
2. There are no pieces between the king and the rook.
3. The king is not in check.
4. The king does not pass through or land on a square attacked by the opponent.

The rook, however, may cross an attacked square. See 7 chess moves that look illegal for the details.

Related terms: Check · En passant · Chess notation