Chessy
What Is Check in Chess?
Check is when a king is under direct attack by an enemy piece, and the player whose king is checked must immediately remove that attack — by moving the king, blocking the attack, or capturing the attacking piece.
Recognizing every response to check instantly is a habit worth building — practice it for free against Chessy's engine.
Play free against the Chessy engine →The three ways to respond
There are exactly three legal responses to check, and no others. You can move the king to a square that isn't attacked, block the check by placing another piece on the line between the attacker and the king (only possible against sliding pieces — bishops, rooks, and queens), or capture the piece delivering the check. Any move you make while in check that doesn't do one of these three things is illegal.
Check is not the same as checkmate
Check simply means the king is currently under attack; the game continues as soon as the threat is dealt with. Checkmate is what happens when a player is in check and has none of the three responses available — no legal move removes the attack, and the game ends immediately. Most checks in a normal game are answered easily and don't lead anywhere near mate.
Rules around check
A few related rules follow directly from what check means. You can never move your own king into check, so any move that would leave your king attacked is illegal, even if it looks tempting. Castling is blocked if the king is currently in check, or if it would pass through or land on an attacked square. And a discovered check — where moving one piece reveals an attack from another — is a common tactical device precisely because it can happen 'for free' alongside another move.
Frequently asked questions
What happens if you're in check and can't respond?
That's checkmate, and the game ends immediately. Check only becomes checkmate when none of the three legal responses — move, block, or capture — is available.
Can you ignore a check and make a different move?
No. If your king is in check, every legal move that turn must remove the check. Any other move is illegal, even if it looks good otherwise.
Can you block a check from a knight?
No. Knights jump directly to their target square, so there's no line to block. A knight check can only be answered by moving the king or capturing the knight.
What is a discovered check?
It's when moving one piece uncovers an attack on the enemy king from a different piece that was previously blocked, delivering check without the moved piece itself attacking the king.