The Chess Variant Pages

Rules of Chess: Castling FAQ

This webpage gives the answers to some frequently asked questions about the official rules of chess regarding Castling. For the full rules of chess, see another webpage.

What is castling?

Castling is a special type of chess move. When castling, you simultaneously move your king, and one of your rooks. The king moves two squares towards a rook, and that rook moves to the square at the other side of the king. For more details, see the rules of chess, or the answers to the questions below.

When are you not allowed to castle?

There are a number of cases when castling is not permitted.
  1. Your king has been moved earlier in the game.
  2. The rook that castles has been moved earlier in the game.
  3. There are pieces standing between your king and rook.
  4. The king is in check.
  5. The king moves through a square that is attacked by a piece of the opponent.
  6. The king would be in check after castling.

Can you castle, if your king has been put in check in an earlier move but is not currently in check, and the king has not been moved?

Yes. Having been in check earlier in the game does not prevent you from castling, as long as the conditions mentioned above are fulfilled.
Or, in a longer form:

Can a king castle after having been in check

Can a player castle if his king was checked earlier in the game? (when the player was checked, he responded by placing another piece between his king and the opponents attacking piece; he did not move the king.) Put another way, does being checked automatically disqualify a player from castling later in the game? (Remember, the king has not moved,the opposing piece was simply blocked by another piece.)

The player can still castle in this situation. The rules of chess state that castling is illegal, when the king or rook has moved earlier, and when in or through check. Having been in check which was removed by interposing another piece, or by taking (not with king or rook that is involved in the castling, of course) the checking piece does not prevent the player from castling later.

Is it allowed to castle which a rook that is attacked or goes through check?

While castling (on the queen side) ,can I castle if my rook passes through check. I'm allways reading that the king may not castle out of ,(through),or into check. I know the rules allways specify ,the king cannot pass through check,but can the rook pass through.
The rook can pass check, or better worded, through an attacked square. I.e., when all conditions that allow castling are met (rook and king have not moved, squares between rook and king are empty, king does not castle from, through, or to check), then castling is allowed, and it is of no importance whether the rook is attacked or goes via an attacked square.

So, when white castles long, a black attack to a1 or to b1 does not make that castling is no longer allowed.

In the diagram above: suppose white king and rooks have never moved. Castling long is legal for white, but in fact the worst move he can make!

Can queens castle?

No. Queens cannot castle.

How many squares do the king and rook move when castling?

There are two types of castling:
  1. Short: On the `kingsside'.
  2. Long: On the `queensside'.
In both cases, the king moves two squares; the rook moves either two or three squares.

Here is an example of short castling. First, white castles short, then black castles short.

And here is an example of long castling. First, white castles long, then black castles long.

Can the King and Rook castle if the rook is threatened by another piece? None of the squares that the king moves through is attacked.

Yes: In this case, castling is allowed, assuming, of course, that the king and rook haven't moved and the squares between king and rook are empty.

How is castling written in chess notation?

Kingside castling (moving the king from e1 to g1 or from e8 to g8) is notated: 0-0.

Queenside castling (moving the king from e1 to c1 or from e8 to c8) is notated: 0-0-0.

Is it correct that a king may not capture when castling?

Indeed. In the above diagram, white is not allowed to castle.

By the way, the rook is also not allowed to capture when castling.

Written by Hans Bodlaender.
WWW page created: April 8, 2002. Last modified: December 18, 2005.