Castling
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Castling moves your king two squares towards a rook, and that rook jumps to the square the king crossed. It is the only move where two pieces move at once. You may castle only if neither piece has moved, the squares between are empty, and your king is not moving into, out of, or through check.
What are the four conditions?
- Your king has never moved this game.
- That rook has never moved this game.
- All squares between the king and rook are empty.
- Your king is not in check, does not pass through an attacked square, and does not land on one.
Kingside and queenside
| Kingside (short, 0-0) | Queenside (long, 0-0-0) | |
|---|---|---|
| White king goes to | g1 | c1 |
| White rook goes to | f1 | d1 |
| Black king goes to | g8 | c8 |
| Black rook goes to | f8 | d8 |
| Squares to clear | 2 | 3 |
| Typical use | Fast, safe, most common | Slower, more aggressive |
The two restrictions people get wrong
You may castle when the rook is attacked, and you may castle out of a pin on the rook. The restrictions apply to the king's journey only. Many players wrongly believe an attacked rook, or a rook that has passed through an attacked square, prevents castling. Neither does.
So on the queenside, the b1 square (or b8) may be attacked and you can still castle, because the king never visits it. Only d1 and c1 matter for White, since those are the squares the king crosses and lands on.
Temporary vs permanent. Being in check right now only stops you castling this move. Once the check is dealt with, you may still castle later. But if you move the king to escape the check, that right is gone forever.
How do I castle on a physical board?
Move the king two squares first, then the rook. Under FIDE rules, touching the rook first can be interpreted as a rook move. Always use one hand.
Frequently asked questions
Can I castle out of check?
No. If your king is in check you must deal with the check another way. You can still castle later, provided the king itself has not moved.
Can I castle if the rook is attacked?
Yes. The restrictions apply only to the king's squares. An attacked rook does not prevent castling.
Can I castle if the king has moved and moved back?
No. Once the king has moved at all, castling rights are lost permanently.
Can I castle with a rook that is attacked on b1?
Yes. For queenside castling the king travels via d1 to c1 and never touches b1, so an attack on b1 is irrelevant.
Which hand should I use to castle?
One hand, king first. Touching the rook first can be ruled a rook move.