How does castling work in chess?
B · Beginner · The board and the pieces · 4 of 10Castling is one move that uses two pieces. The king goes two squares towards a rook, and that rook jumps to the square the king crossed. Neither piece may have moved before, and the squares between them must be empty. The king must not be in check, cross an attacked square or land on one.
How it works
- The move: the king moves two squares along the first rank towards the rook, and the rook goes to the square the king crossed.
- It counts as: a single move of the king.
- Lost for good: if the king has already moved. With a rook that has already moved, castling with that rook is lost.
- Not while in check: the square the king stands on must not be attacked.
- Not through check: the square the king crosses must not be attacked.
- Not into check: the square the king lands on must not be attacked.
- Nothing in between: no piece of either colour may stand between the king and the rook.
- Touch the king first: a player who touches the rook first may not castle on that side on that move.
The glossary has castling, the king, the rook, the check, the touch-move rule and the illegal move.
Tricky cases
The king was in check earlier, moved nothing and the check was blocked. Can it still castle?
Yes. Having been in check does not remove the right. Only the king or that rook having moved does.
The rook is under attack, or would pass over an attacked square. Can the player castle?
Yes. The three squares that matter are the king's: where it stands, the one it crosses and where it lands. The rook may be attacked.
A player picks up the rook first, then the king. Is that castling?
No. A player who deliberately touches a rook and then the king "is not allowed to castle on that side on that move" and must move the rook.
A player castles using both hands and presses the clock. Is that all right?
No. Each move must be made with one hand. A two-handed move followed by pressing the clock is penalised as an illegal move.
Why the rule exists
The king starts in the middle, where the fighting opens up first. The rooks start shut in the corners. Castling fixes both problems in one move. The limits stop it from being an escape hatch: a king cannot castle its way out of an attack.
Where it differs
| Where | What changes | Source |
|---|---|---|
| King has moved | No castling for the rest of the game | FIDE Laws 3.8.2.1 |
| One rook has moved | No castling with that rook | FIDE Laws 3.8.2.1 |
| King attacked, or crossing or landing on an attacked square | Not allowed for now | FIDE Laws 3.8.2.2 |
| Piece between king and rook | Not allowed for now | FIDE Laws 3.8.2.2 |
| Chess960 | The king and rook finish on the same squares as in regular chess, wherever they started | FIDE Laws, Guidelines II.3 |
From the rule book
FIDE, Laws of Chess (approved 7 August 2022, applied from 1 January 2023), Articles 3.8, 4.1, 4.4, 4.7.2 and 7.5.4 and Guidelines II.3. Checked 14 October 2026. Official document: FIDE Laws of Chess taking effect from 1 January 2023 (FIDE Handbook E.01).