It makes you like one of those cool guys who spam 3|2 blitz and 5 min blitz on cc and lc
Is it legal to move your rook without moving your king if castling is a legal move?

what marcyful said:
once you have clicked on the king, you must click the king again or try an illegal move with the king (your 2 options for removing the highlight from the king) BEFORE clicking on your rook, as otherwise the board is programmed to attempt castling (clicking king, then rook will ALSO castle, along with the standard method of moving the king 2 squares over toward the rook you wish to castle with).
if castling itself is an illegal move in this situation (if your king would castle out of, through, or into check, OR if either the king or the CASTLING rook have moved previously already, EVEN IF you move them back into position) then castling will of course not occur anyways in this situation.
please note (if anybody reading this does not know) that the castling ROOK itself CAN legally move out of, through & onto attacked squares during the castling move & if you move 1 rook but NOT the king, you CAN still castle with the other (unmoved) rook.

So far I've tried to move my rook in 3 games, but it forced me to castle, and I got checkmated almost immediately because of it. Is it a legal move to move a rook that also has castling as a legal move? I have done it many times OTB but my opponents said nothing about it.
Wait…how do you accidentally castle over the board…..

1. There are no pieces in between the King and Rook.
2. Castling must be the first move for both pieces. If you move the King, you forfeit the right to castle to either side. If you move a Rook, you forfeit the right to castle to the side that Rook was on.
3. The act of castling cannot put your King into check nor can you pass through check. This means even though the final landing square is not being threatened the square in between also cannot be threatened. This also means you cannot castle to get out of check.
4. If the above conditions are met, in OTB (a computer will also enforce this), the King must be moved to the right or left two squares first, then the Rook is moved next to the King. The Rook cannot be moved first, this is to prevent the misunderstanding of the original intent, since a King can only move two squares when castling it is clear to intent is to castle; however, a Rook can be moved multiple squares, so the player could have changed their mind shortly after moving the Rook and decided to castle instead.
I am guessing one of those conditions were not met that prevented you from being able to castle. I highly doubt there is a flaw in the program that prevented you from castling when you had a legal right to. I hope this clears up any confusion.

what marcyful said:
once you have clicked on the king, you must click the king again or try an illegal move with the king (your 2 options for removing the highlight from the king) BEFORE clicking on your rook, as otherwise the board is programmed to attempt castling (clicking king, then rook will ALSO castle, along with the standard method of moving the king 2 squares over toward the rook you wish to castle with).
I really wish the click king then rook to castle is a toggleable option, cause I have lost quite a number of games where I accidentally castled to a side swarming with the opponent's pieces.

if you get into the habit of deselecting a piece once you decide NOT to move it (by either performing an illegal move with the piece OR clicking on it again so that it is no longer highlighted), then accidental castling will never be an issue.
i suggest the first method (make sure it's an illegal move!), as that removes the possibility of accidentally reselecting the king with an extra click. please note that it is impossible to castle by moving the ROOK & dropping it on the KING, although the reverse IS possible.
So far I've tried to move my rook in 3 games, but it forced me to castle, and I got checkmated almost immediately because of it. Is it a legal move to move a rook that also has castling as a legal move? I have done it many times OTB but my opponents said nothing about it.