Questions tagged [illegal-move]

A move that doesn't respect the rules of chess.

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Handling Illegal Moves by Both Players in a Blitz Game: Rules and Arbiter's Role

In a recent blitz chess game, a situation left me uncertain about the official rules and how they are enforced. Both players, including myself, made illegal moves, but these were not immediately ...
Iman Mohammadi's user avatar
3 votes
1 answer
332 views

How many illegal moves are allowed in Classical, Rapid & Blitz?

As of Jan-2024, I see that 2 illegal moves are allowed in chess and the 3rd one results in a lose of the game by the one who made those. FIDE 7.4b After the action taken under Article 7.4.a, for the ...
iammilind's user avatar
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3 votes
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What is the result if a player has insufficient material and the opponent plays two illegal moves?

Suppose player X has only a king. Their opponent has played two illegal moves during the game. Is it a draw or does X win?
iammilind's user avatar
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How to detect an illegal position?

There are many positions in chess that are illegal in the sense that they cannot be reached by legal moves. Is there an algorithm to detect if a position is illegal or not?
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2 votes
2 answers
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Official knight move rule definition

Not a trivial question: How would you define the knight move rule on a d-dimensional chessboard (say an 8 X 8 X ... X 8 board) by extending the official knight move rule that states how a knight moves ...
Marco Ripà's user avatar
4 votes
0 answers
118 views

How often do strong master level players (2400+) make illegal moves?

In the latest podcast from the Chicken Chess Club, Laurent Fressinet admitted that in his latest tournament, the French rapid and blitz championships, he made an illegal move. He asked the other two ...
Brian Towers's user avatar
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2 votes
2 answers
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Is there a website that records the moves of a chess game in video or gif format, and also allows illegal moves?

I've wanted to record some chess games in 2d video or gif form from a version that I made that has different rules, but it won't allow me to import it because it has illegal moves. Is there a way to ...
joca9's user avatar
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4 votes
1 answer
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Term to distinguish between two categories of illegal positions

Consider these two categories of illegal positions. First, e.g.: Not having exactly one King of each color Both Kings being in check Pawns on the first or eighth ranks Second, e.g.: Having more ...
Joseph Sible-Reinstate Monica's user avatar
5 votes
1 answer
1k views

Can someone press the clock without making a move to avoid getting flagged in 2022?

As the title says let's say it is a 1 hour 30 minute game with 30 seconds increment/move. Now if someone deliberately presses the clock at the last second without moving to avoid flagging and get the ...
cmgchess's user avatar
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2 votes
2 answers
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USCF: Should the arbiter correct illegal moves without a player claim?

Should an USCF arbiter correct illegal moves without a player claim? Here is the USCF link: USCF rules of chess Here is the FIDE link: FIDE rules of chess USCF and FIDE rules are NOT 100% equal. What ...
Beginner's user avatar
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7 votes
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Why isn't legal move filtering done at search time?

Most engines have some method of filtering out pseudo-legal moves from the actual legal ones. However, is there any reason not to keep them? With bit-boards, you can quickly filter out the ones that ...
AAce3's user avatar
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3 answers
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"Highest" level of illegal move

For example, was a GM ever caught on an illegal move? Of course, only standard time control (everybody still remembers Carlsen-Inarkiev, but that was a blitz game) and after FIDE codification of chess ...
Hauke Reddmann's user avatar
1 vote
1 answer
1k views

Is this move illegal?

I'm currently writing my own chess game with my own AI and have a Question about a move: Here, Purple moved his Pawn from F2 -> F3, which allowes the Green Queen on H4 to capture the King, and I ...
Kerialstraz's user avatar
8 votes
1 answer
398 views

Ignoring Touch Move results in an Illegal Move?

I just wanted to clarify the following incident: When touching a piece without expressing the intend to adjust its position (cf. 4.2.1 FIDE Laws of Chess), such that it has to be moved because there ...
Fabian's user avatar
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6 answers
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Is blocking a check with a check an illegal move?

Say my opponent puts me in check. If I move my queen to block the check and it also puts my opponent in check, is that legal?
John's user avatar
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1 answer
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5D Chess - Why is white king not in check in this position?

Why cannot black rook on c5 in the bottom timeline capture the king on c5 in the top timeline? Why is the king not in check?
Robert Lee's user avatar
11 votes
1 answer
2k views

Series of illegal moves in check

This question falls under FIDE rules (USCF answers/comments welcome). If I make an illegal move leaving myself and my opponent in check, hit the clock and my opponent misses it and then continues play ...
Aaron's user avatar
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1 answer
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Can a player win if their opponent has made 2 illegal moves, but a helpmate isn't possible?

Suppose that in a KQ vs. K endgame (or in an endgame where Black can't possibly mate the other side), White makes two illegal moves. Can Black claim a win?
double-beep's user avatar
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4 votes
3 answers
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Is this an illegal chess move?

Can the White king move to g2 to checkmate? 8/8/8/8/4Q3/7k/5K2/8 w - - 0 1 1. Kg2
ImABigDummy's user avatar
11 votes
4 answers
6k views

Can I hover my finger over a chess piece without touching it in a major chess tournament?

Noob question: I am aware of the no-touch rule, but can I point or hover my finger over a chess piece in a major tournament? To clarify, let's say it's my turn and I am thinking about which piece to ...
Aevil1's user avatar
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1 answer
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Touch move and capture sequence

When considering the touch move rule, I am still unclear about the legal sequence for a capture. Example, white intends to capture a took on a8 with rook on a1 (open file). Does white have to touch ...
theBIOguy's user avatar
1 vote
1 answer
254 views

How is this move illegal?

I'm black and it's my turn. I'm playing in the Arena chess player against Stockfish. This is my current board: [fen ""] [startply "31"] 1. e4 d5 2. exd5 e6 3. dxe6 fxe6 4. Nf3 Nf6 5. Bc4 c6 6. O-O ...
chronoUnknown's user avatar
3 votes
1 answer
1k views

Illegal move or checkmate? [duplicate]

I was playing chess with an opponent. He had his queen in front of his king. I attacked the queen and he moved her, exposing his king directly to my rook. It was my turn to move, not his. We couldn't ...
Clement's user avatar
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8 votes
2 answers
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FIDE rules when opponent accidentally promotes to your Queen

This happened to someone else recently in a time scramble during an OTB game. His opponent promoted a pawn and placed a Queen of the wrong color on the board. He was corrected by the player and the ...
Jeroen's user avatar
  • 398
6 votes
1 answer
555 views

We found out that we made an illegal move later on in the game [duplicate]

I am playing with my friend. I didn't notice that my king was in check, so I made an illegal move. We noticed this after several more moves. What should happen next? Do we restart the game or ...
Usman Siddiq's user avatar
3 votes
1 answer
153 views

How to detect invalid pawn structures (not based on opponent material) for FEN valdation?

I'm going to further expand a FEN validation function I have been working on for some time to include illegal pawn formations such that: ... for example white pawns could never be on a2, a3, and ...
ajax333221's user avatar
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4 votes
1 answer
347 views

How can I use pgn-extract to remove a game from a pgn file when there is an illegal move?

How can I use pgn-extract to remove a game from a pgn file when there is an illegal move?
leo's user avatar
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2 votes
3 answers
697 views

How to notify check when a player leaves himself in check

I'm learning to play chess. Twice we had a situation where the white player moved a piece that was blocking the black Queen from checking the white King. There was no move available to announce "...
Brian's user avatar
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6 votes
1 answer
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Can a win be claimed on the second illegal move if the first wasn't raised?

First of all, I don't think this is a duplicate of what happens on the first illegal move in a game. This is what happens after the second if the first is unclaimed. The setting is a tournament under ...
Remellion's user avatar
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2 answers
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In a tournament game, what should a player do if he find that his opponent's position is impossible, which was caused by an earlier illegal move? [duplicate]

For example, if a player realises that his opponent has two bishops of the same colour after a certain legal move (and assuming that it is clearly not caused by any pawn promotion), which implies that ...
Zuriel's user avatar
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0 votes
4 answers
1k views

Blitz Touch Move Rule

In a "friendly" blitz game I got into an argument with my opponent in the following scenario: My opponent's knight was pinned to his king. He did not notice and touched his knight to move it. I ...
Daniel Vieira's user avatar
3 votes
1 answer
1k views

What happens if a player makes an illegal move and nobody notices?

What happens if a player makes an illegal move (i.e. a realistic case could be, he castles after he already moved the King), but none of the player notices, and the game goes on and on for a lot of ...
A. N. Other's user avatar
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-1 votes
1 answer
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Checking on the legality of a move [duplicate]

I moved my white King to d4, taking black's bishop. This put the king in a checkmate with black's knight on c6. Is this move legal or illegal? Thank you.
jsweede's user avatar
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2 votes
3 answers
2k views

What happens if I push a pawn to the 8th rank and press the clock before promoting? [duplicate]

What happens if I push a pawn to the 8th rank and press the clock before converting it to another piece? Does it make a difference if it's Blitz or not?
Pedro A's user avatar
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6 votes
2 answers
1k views

Can I move a piece protecting the king if it keeps protecting on its new location?

Situation: there's a piece between the king and an opponent’s piece. If this piece were not there, it would be a check. If I were to try and move the protecting piece somewhere and leave the king ...
Dan's user avatar
  • 163
100 votes
12 answers
51k views

Why is it illegal to castle with both hands?

I was watching the match between Ian Nepomniachtchi vs Hikaru Nakamura and Nakamura used both hands to castle. Why is it illegal to castle using both hands? What's wrong with that?
tah's user avatar
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-3 votes
2 answers
348 views

What happens if I realize that I made an illegal move? [closed]

Say I somehow make an illegal move, what happens? If I realize, can I then take it back, and make it legal? If so, how?
tah's user avatar
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3 votes
1 answer
370 views

Are there any legal positions known to be impossible to come to in a normal game? [duplicate]

There are some fairly obvious ways to set up a chess board that cannot possibly happen: both kings simultaneously in check would be one. There are some positions that seem impossible in a normal ...
user1833028's user avatar
7 votes
3 answers
14k views

Can a king be checked with another king when checking square is protected by the side which gives the check? [duplicate]

Can a white King move next to a black King to check it, if there is a white pawn protecting the white King, preventing the black King from taking the white King?
David's user avatar
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8 votes
1 answer
1k views

Illegal Move Missed-Too Late?

This question is about standard games under USCF rules (if FIDE is different, I'd like to know). Say that one side makes an illegal move-specifically, castling through check. Neither player notices. ...
Steve Weber's user avatar
1 vote
3 answers
1k views

Capturing the king in a blitz game

In a blitz game, when my king is checked, I make an illegal move that checkmated the opponent and pressed the clock. Then my opponent captured my king and claimed victory. Capturing the king is not a ...
melody's user avatar
  • 21
23 votes
1 answer
6k views

The illegal moves in Carlsen-Inarkiev

In the first round of the World Blitz Championship in Riyadh. Magnus Carlsen played Ernesto Inarkiev and the game ended strangely. [FEN ""] [StartPly "53"] [Event "World Blitz ...
user1583209's user avatar
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-3 votes
1 answer
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Illegal promotion in FIDE blitz game? [duplicate]

In a FIDE rated blitz (3+2) tournament (following the official FIDE rules), the following position occurred: [FEN "8/1k5P/q7/8/8/8/6K1/6Q1 w - - 0 1"] White played 1.h8Q. But since both queens were ...
SmallChess's user avatar
  • 22.5k
5 votes
1 answer
756 views

Can you claim an illegal move in Blitz after pressing your clock (but without making a move)?

In Blitz under FIDE rules, Player A makes and completes an illegal move by pressing the clock. Player B states that Player A's move is illegal, does not make a move, but quickly presses his own clock, ...
Curious's user avatar
  • 51
6 votes
2 answers
3k views

Detect pinned pieces code

This post is a follow up of this one: C++ vs Java Engine move generation performance My goal here is to improve the performance of my move generator, which finishes perft (start_pos, 6) in 8.5 secs. ...
Fernando's user avatar
  • 425
25 votes
6 answers
5k views

Are there any illegal positions that are difficult to spot?

I have a question and I'm sorry if it sounds very uninformed, I'm not a professional chess player so my interest is mere curiosity. I was wondering if there are examples of illegal positions that ...
seawalker's user avatar
  • 359
2 votes
1 answer
2k views

Check and checkmate on following moves

I was playing chess with a buddy, and I put him in check. On the following move, without moving his king out of check, he moved a rook to put me in checkmate. My questions are as follows: Can he ...
Buck_x20x's user avatar
8 votes
4 answers
1k views

How to create PGN notation with wrong moves in it?

I was as chess trainer with some young guys on a tournament, and wrote down some of their games. In nearly every game, there were wrong moves in it: king is in check, but does not move or react; ...
mliebelt's user avatar
  • 497
0 votes
1 answer
282 views

Rook and knight used together within the same move - legal?

This is my first question on chess beta and I don't know if I'm insane or if the cpu is broken. So I was playing chess against a CPU on the iPhone with the app 3D Chess Game, and the CPU (playing ...
rappatic's user avatar
  • 129
9 votes
2 answers
2k views

Touch a piece and then claim opponent's previous move was illegal

In a last round tie between 2 players fighting for top seed in a competition, here is what happened. White had 18 seconds on his clock and black had 26 seconds. Black was winning. At move 56, black ...
oziomajnr's user avatar
  • 517