What happens if you make an illegal move in chess?

If the clock has been pressed, the arbiter restores the position from before the illegal move and the player must play a legal move, with the same piece if it can move legally. The opponent receives two extra minutes in classical chess and one in rapid. A second illegal move by the same player loses the game.

Do you lose if you make an illegal move in blitz?

Not for the first one. Since 2018 a first illegal move in rapid or blitz is corrected and the opponent receives extra time, one minute in most blitz events. A second illegal move by the same player loses the game. In blitz without an arbiter at every board, the opponent must claim before making their own move.

Is it an illegal move if you have not pressed the clock?

The move is wrong, but under Article 7.5.1 it is completed, and penalised, only once the clock has been pressed. Before that, the player takes it back and makes a legal move. The touch-move rule still applies, so the piece that was touched must be moved if it has a legal move.

What happens if nobody notices an illegal move?

In a game with full arbiter supervision, the position is put back whenever the illegal move is discovered during the game. In rapid and blitz without that supervision, the opponent must claim before making their own next move. If neither the arbiter nor the opponent acts in time, the illegal move stands and the game goes on.

Library / Rules / Illegal move

Rule · FIDE Laws of Chess · Article 7.5

Illegal move

A move that breaks the rules of piece movement in Articles 3.1–3.9 of the FIDE Laws. Once the player has pressed the clock, the position is put back, a legal move is played instead, and the opponent gets extra time; a second illegal move by the same player loses the game.

Quick answers

What happens if you make an illegal move in chess?: If the clock has been pressed, the arbiter restores the position from before the illegal move and the player must play a legal move, with the same piece if it can move legally. The opponent receives two extra minutes in classical chess and one in rapid. A second illegal move by the same player loses the game.
Do you lose if you make an illegal move in blitz?: Not for the first one. Since 2018 a first illegal move in rapid or blitz is corrected and the opponent receives extra time, one minute in most blitz events. A second illegal move by the same player loses the game. In blitz without an arbiter at every board, the opponent must claim before making their own move.
Is it an illegal move if you have not pressed the clock?: The move is wrong, but under Article 7.5.1 it is completed, and penalised, only once the clock has been pressed. Before that, the player takes it back and makes a legal move. The touch-move rule still applies, so the piece that was touched must be moved if it has a legal move.
What happens if nobody notices an illegal move?: In a game with full arbiter supervision, the position is put back whenever the illegal move is discovered during the game. In rapid and blitz without that supervision, the opponent must claim before making their own next move. If neither the arbiter nor the opponent acts in time, the illegal move stands and the game goes on.

An illegal move is any move that breaks the rules of how the pieces move: a king left in check, a bishop that jumps over a pawn, castling through an attacked square, an en passant capture played a move too late. The FIDE Laws of Chess treat it as an irregularity to be corrected. The board goes back to the position before the move, the player makes a legal move, and the opponent is compensated with extra time on the clock. A player who does it a second time in the same game loses.

What happens after an illegal move?

The position from immediately before the illegal move is put back on the board. The player who made it must then play a legal move, and because the touch-move rule still applies, it must be made with the same piece if that piece has a legal move. The arbiter adds time to the opponent’s clock: two minutes in a classical game, one minute in rapid. If the same player completes a second illegal move in the game, the arbiter declares the game lost, unless the opponent cannot checkmate by any series of legal moves, in which case it is a draw.

The exact rule

Article 3.10 of the Laws defines the term: a move is illegal when it fails to meet the requirements of Articles 3.1 to 3.9, the articles that describe how each piece moves, how castling, en passant and promotion work, and that a player may never leave or put their own king in check.

Article 7.5 then sets out what follows:

7.5.1. An illegal move is completed once the player has pressed the clock. If it is found during the game that an illegal move has been completed, the position immediately before the irregularity is reinstated, and the touch-move rules (Articles 4.3 and 4.7) apply to the move that replaces it.

7.5.2. A pawn moved to the last rank and left there as a pawn, with the clock pressed, is an illegal move. The pawn is replaced by a queen of the same colour.

7.5.3. Pressing the clock without making a move is penalised as if it were an illegal move.

7.5.4. Using two hands to make a single move, for example in castling, a capture or a promotion, and then pressing the clock, is treated as an illegal move.

7.5.5. After the first completed illegal move, the arbiter gives the opponent two minutes of extra time. After the second completed illegal move by the same player, the arbiter declares the game lost by that player. The exception is the same as for a flag fall: if the opponent cannot checkmate by any possible series of legal moves, the game is drawn.

The moves that are illegal

Most illegal moves in real games fall into a few families.

Moving into check, or ignoring one. The king may never stand on an attacked square at the end of a move. This covers walking the king next to the opposing king, moving a pinned piece off the line it shields, and answering a check with a move that does nothing about it.

Castling when the conditions are not met. The king or rook has already moved, the king is in check, or the king passes over or lands on an attacked square. Each of these makes castling illegal; the full conditions are on the castling page. Touching the rook before the king is a separate matter, handled under the touch-move rule.

En passant at the wrong time. The capture is allowed only on the move immediately after the enemy pawn’s two-square advance. Played one move later, it is illegal. See en passant.

Wrong piece movement. A bishop on the wrong diagonal, a rook passing through a piece, a pawn capturing straight ahead. These happen mostly when a player misreads the board in time trouble.

Mechanical errors that the Laws count as illegal. A pawn pushed to the last rank without being replaced, a move made with two hands, a clock pressed with no move made. None of them involves a wrong square, but Article 7.5 penalises all three in the same way.

Before and after the clock is pressed

The clock press is the line the rule turns on. A player who puts a piece on an illegal square and notices before pressing the clock has not yet completed the move. There is no time penalty: the player makes a legal move instead. The touch-move rule still binds, so if the touched piece has a legal move, that piece must be moved.

Once the clock is pressed, the illegal move is complete and Article 7.5.5 applies. This is why arbiters stop the clocks when they see an illegal move: they reinstate the position, adjust the clocks, and restart the game.

Rapid and blitz

Rapid and blitz follow the same structure with two differences.

The penalty is smaller. Article A.3 sets the penalties of the Competitive Rules at one minute instead of two for rapid games. Blitz events run under the rapid laws unless each game has its own arbiter (Articles B.2–B.4), so in the usual blitz tournament the opponent also receives one minute. The event regulations state which set applies.

Someone has to act in time. When an arbiter is not watching every game, Article A.5.2 applies. The arbiter acts on an illegal move only if the opponent has not yet made the next move. If the arbiter does not intervene, the opponent may claim, again provided they have not moved yet. If neither happens, the illegal move stands. After the opponent has moved, the illegal move can be corrected only if both players agree.

The practical advice follows from that last point: if you see your opponent make an illegal move in a rapid or blitz game, stop the clock and call the arbiter before you make your own move.

The pre-2018 rule

Until 2017, a single illegal move in rapid or blitz lost the game if the opponent claimed it correctly. From January 2018 FIDE brought rapid and blitz into line with classical play, so the first illegal move costs time and only the second costs the game. Some older club rulebooks and online articles still describe the old rule, so it is worth checking the date of any source.

Online chess

Chess servers do not accept illegal moves at all. The software only lets a piece go to a square it can legally reach, so a player can never leave a king in check or castle through an attacked square. The penalties in Article 7.5 matter only over the board, which is where players who learned on a screen tend to meet them for the first time.

Edge cases

What if the illegal move is noticed many moves later? In a game under full supervision, Article 7.5.1 still applies: the position before the irregularity is reinstated whenever the illegal move is found during the game. In rapid or blitz without that supervision, it can only be corrected by agreement between the players.

Does an illegal move that gives checkmate win? No. Article 5.1.1 ends the game on checkmate only when the mating move was made in accordance with Article 3 and Articles 4.2–4.7. The position is restored and the player must find a legal move.

What if both players make an illegal move? Each player’s illegal moves are counted separately. One illegal move each costs each player time, and only a player’s own second illegal move loses the game.