Castling in Chess: What is it, Rules and Benefits

Chess terms

Castling in chess is a special move allowing players to put their King in safety. This special occasion includes moving both the King and the Rook in one move. Once players castle, they put their King into a safe spot and activate their Rooks. There are two sorts of castling: the Castling Kingside (also called short castle) and the Castling Queen side (also called long castle). The Kingside Castling is notated as either “O-O” or “0-0”, and the Queenside Castling is notated as “O-O-O” or “0-0-0”.


The upper diagram shows a castling king side (“4. O-O” or “4. 0-0”)

How does Castling Work?

It is performed by first moving the King two squares towards the rook on the first rank and placing the Rook on the one square adjacent to the King’s opposite side. The King has to be moved first, and Rook has to jump above it to get to the other side.

If the White player short castles, they put the e1-King to g1 and h1-Rook to f1 in the same move.

Example of Short Castling

Example of short castling

If the White side long castles, they put the e1-King to c1 and the a1-Rook to d1. The same applies to the Black side (symmetrical). Certain rules should be met to be able to castle.

Example of Long Castling

Example of Long Castling

What are the Castling Rules?

There are several rules that can enable or disable the castling for the player:

 1) To castle, both the King and the Rook (the Rook is located where the castling is desired) shouldn’t be moved before.

In the diagram above, we can see that the White King is already moved to e2-square. From this moment on, White can never castle during this game.

Different from the King, if one of the Rooks is moved, the King can still castle on the opposite side. In the diagram above, the h1-Rook has moved to g1-square. The King can no longer be safe in the Kingside. The best option is to castle in the Queenside.

 2) There mustn’t stand any pieces between the King and the Rook.

f1-Bishop stays in between the King and the Rook.

Castling Rule 2

In order to castle, the King and Rook have to be fully connected. There cannot be any piece standing in between them. The player needs to be able to shift the King two squares toward the Rook. Hence, developing pieces is one of the vital steps in the opening stage to protect the King.

 3) The King shouldn’t be under check.

b4-Bishop checks the White King. White cannot castle under check.

Castling Rule 3

As shown in the above diagram, the King cannot castle if it’s under a check. This doesn’t mean the King cannot castle anymore. Once the threat is gone, White can still castle. In the given position, White can play c2-pawn to c3 and block the check. Then, they can castle if they desire.

 4) The squares on which the King will move forward to castle cannot be attacked by any enemy pieces.

Castling Rule 4

In the diagram above, the c5-Bishop covers the g1-square. Both f1- and g1- should have been secured by White to castle. The only way to castle here is to block that threat on g1. The player can try c3-and d4-pawn pushes to close the diagonal. It is important to note that moving the f-pawn often creates scenes like this where the King cannot easily castle.
Note – If the Rook is under assault, this does not prevent the side from castling.

Benefits of Castling

One of the main opening principles is castling early. This principle comes from the problems that can be caused to the King once it resides in its initial location. The King is the most essential piece, and it should be prioritized. Games often involve pawn pushes such as e4 and e5. This increases the probability of enemy pieces creating a threat to the King. The King is in the castled square, making it harder for the rival to launch a deadly attack without signs. The fortress of pawns in front of it protects it as if it’s at his own home. Once the King is castled, the Rook also gets into the game. It can be placed in a useful file, benefiting the player greatly. As we know, Rooks are the most valuable after the Queens. Bringing them to the game is also quite challenging because they are located at the corner squares. This one special move does it all

When Should You Castle in Chess?

At low levels, players should always castle immediately after the pieces nearby the King are developed. Castling move should not be delayed if the enemy prepares to attack the King and the e-file is open. Playing risky moves like f4 should be done after the player castles. Once the King is moved before castling, it is very rough to make it safe. Players must ensure they always have enough time to castle before it’s too late. Also, castling can be an aggressive tool. There are many games showing that by only castling, the player can contribute the Rook to the action. Even if the player has a fierce assault on the rival King, castling will make sense.

Common Castling Mistakes to Avoid

1. Castling with two hands

This mistake does not occur in online games. However, in an over-the-board tournament, the players need to castle with one hand. The King has to be moved first, and then Rook should be placed adjacent to the King. Castling with two hands is considered a rule violation.

2. Castling into checkmate

Although this is not a rule violation, players must be careful that the castled King is safe. The opponent can create an attack towards that square. The assault should be assessed, and King should be safe once it’s castled.

3. Castling the wrong side

There are specific positions where the enemy has too many pieces on that side. Castling the risky side could be a problem in maintaining the safety of the King.


Castling is a special chess move that allows the King to be safe behind the pawn fortress. There are several rules to know for conducting this special move. Players should castle on the safe side and maintain their King’s safety.

Frequently Asked Questions (FAQ)

What does castling mean in chess?

Castling is a special move to put the King in safety. It involves the King and Rook moving in the same turn. Players often castle to maintain the advantage of this special move. The castled side’s Rook also gets into the game and is activated after the player castles the King.

When was castling added to chess?

Although the specific date is unknown, it is thought that it was added to chess in the 1300s. In the 1600s, it was reformed to the form we use today.

Is castling allowed in chess?

Yes, castling is allowed in chess. However, there are specific rules that allow or disable players from castling. These rules can either irreversibly prohibit the castling in a game or forbid it momentarily.

Written by
Emre Sancakli, Сhess Coach
has a rating of 2400+ on and, making him one of the top 5000 players in the world. He teaches many chess enthusiasts and even creates educational courses. As a writer, he keeps bringing his 'A game' to the content you will face on this website.
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