I am new to chess. I have tried to learn checkmate from the video lesson in chess24 website. There, in one question, it marked my answer wrong and said that it was not checkmate. Can anyone please explain the reason ?


I do apologize if I asked anything stupid. Thanks in advance.

  • 11
    It's mate! Don't trust computers over your instinct!
    – David
    Aug 8, 2020 at 16:05
  • 11
    It’s funny that the move is written down at Qc8#. Not Qc8+ or just Qc8, but Qc8#. In their analysis line they acknowledge that your move is mate.
    – DongKy
    Aug 8, 2020 at 23:10
  • 31
    @David That's terrible advice. The issue here is the person who programmed the computer, not the computer itself. Aug 9, 2020 at 5:03
  • 5
    @Acccumulation Could you put me an example of a computer that wasn't programmed by a person?
    – David
    Aug 9, 2020 at 13:51
  • 5
    @David: Some computer programs are known to be good and worth using. Random websites don't always fall into that category. Given software that has been established as trustworthy, using it to be sure you're not missing a possible move is generally a good idea. So yes, it all comes down to establishing trust. When a computer gives a different result than you think is correct, you need a tool that can tell you why you're wrong (e.g. by showing a legal move for black, if this situation had been reversed and you thought it was mate but it actually wasn't). Aug 9, 2020 at 18:55

9 Answers 9


Welcome to Chess Stack Exchange.

I believe you're doing well here. It is surely a checkmate. Probably the website isn't programmed that way to recognize that move. But, as per your question, this is clearly a checkmate that resembles the one-rook-mate pattern.


The sidebar says "1. Qe7# (1. Qc8#) (1. Qb8#)".

In case you're not yet familiar with chess notation, this means:

  • 1​. (White's move number 1)
  • Q (the Queen)
  • e7 (moves to space E7)
  • # (and checkmates.)

After that, your move "(1. Qc8#)" is highlighted in red, indicating it was not one of the answers they were looking for. But note that it is given the checkmate mark (#), confirming that your move in fact a correct move, one that they simply forgot to include in the list of answers.

"(1. Qb8#)" written at the end is an additional move which are equally as valid as the first one. Qc8# should have been included here, but it was mistakenly left out.

  • 11
    For a full explanation of this notation, the magic words to put into Google are "algebraic chess notation."
    – Kevin
    Aug 9, 2020 at 3:14
  • 4
    The move Qc8# is in red, which on chess24 means that it was played by the user but was not one of the solution moves. So the problem is actually that Qc8# is missing from the solution (despite the text saying “White has three moves that give checkmate”).
    – Stephen
    Aug 9, 2020 at 12:09
  • @Stephen it's strange that it is able to recognize that of the solutions listed the user performed that one but also not recognize it as right (despite it being a solution). Almost like there's two variables in the programming like 'accepted answers' and 'displayed accepted answers' or something? Very weird. Aug 10, 2020 at 12:42
  • @CaptainMan: Qc8# isn’t one of the solutions listed. That was the point of my comment, though perhaps I didn’t express it very clearly. If the user plays a move that isn’t one of the listed solutions, then chess24 inserts this move into the list of solutions, showing it in red to make it clear that it was wrong. That is what happened here - there are only two solutions listed, plus the “wrong” move Qc8#.
    – Stephen
    Aug 10, 2020 at 14:27
  • 1
    @Mohirl: Yes it says there are three solutions, but they forgot to add one of them. If the user plays any move other than Qe7# or Qb8#, it will be displayed in red along with 1.Qe7# and 1.Qb8#. (I haven’t tried this in this particular exercise, but this is how puzzles on chess24 work in general - and this isn’t the only one where they missed out a checkmate.)
    – Stephen
    Aug 10, 2020 at 17:48

That is checkmate. You are simply using a bad tool.

For simple mate in one exercises I recommend my own website. For example, this link https://www.apronus.com/chess/puzzles/mate-in-1/?2vs1 has mate in 1 puzzles where the stronger side has two chessmen against a lone king. The good points about my system are:

(1) all alternatives are accepted,

(2) if you play an incorrect move then the computer will simply reply with a move that demonstrates that there was no checkmate after your first move.

Moreover, you can study the checkmate position by trying to make moves with the checkmated side. Then you will see arrows pointing to moves that would capture the king.

You can also move on a step further and try to solve puzzles where the task is to avoid getting mated on the next move. For example https://www.apronus.com/chess/puzzles/mate-in-1-avoid/?2vs1 has the same positions as the first link but now you play with the lone king to avoid mate.

More puzzles for beginners are listed on the table of contents at https://www.apronus.com/chess/puzzles/


That is indeed checkmate, I've been playing chess for months.

It must be an issue with either the code (which is probably the problem), or the client or server (which is very unlikely, but could be the case). There are other chess websites where you can learn, such as https://lichess.org/learn#/ and https://www.chess.com/lessons.

Those should work better, while they still have a few problems, it's not really too much.


The website (or that chess problem on that site specifically) is clearly buggy.
All 3 of the moves listed as correct answers are mates, and even shown with #
Qe7# Qc8# Qb8#

My guess as to what happened:

  • The web site supports various different kinds of problems, including "one correct move".
  • It doesn't have a chess engine checking for mates, just that they match some pre-programmed answers. It relies on humans to set up the correct-answer conditions separately from the question and answer text. (Introducing the possibility of human error causing this problem.)
  • A human entered correct problem and answer text, but accidentally marked it as only the first answer being correct. Or some kind of syntax error or other mis-use of the problem-setting tools that made the website not understand that any of the answers were valid.

That would explain why all 3 listed moves have a # checkmate symbol after them: those are manually-entered text, and the web site doesn't truly know they're checkmates. Or doesn't know that they question is looking for checkmates, because programming that is separate from writing the text.

In future, if you encounter something online that seems to be telling you something that seems wrong, you can load up the position in a chess engine you trust and try it. Maybe you'll find there was a legal move you didn't spot.

As a beginner (or for any human) it's certainly possible to make mistakes. But this case is simple enough that it's pretty easy even for me (very much non-expert) to be pretty sure that all 3 of those moves are mates, and that there aren't any other mates. But it wouldn't take much more complexity for me to not be sure if a problem was buggy or if I was missing something.

In this case, the 3 listed moves that pop up being shown with # makes it fairly clear it's a bug, though.


While everyone is correct here in assuring you this is a checkmate and the tool is wrong , I am not seeing them explaining how you could verify this and since you are learning this might be useful to you:

  1. The black king is indeed in check by the white queen as the white queen can move anywhere on row eight
  2. The black king does not have any moves where it would not be in check. It has five possible moves, two to the row eight which , as we just noted, are covered by the white queen and three to the row seven all of which are covered by the white king.

For example moving the queen to D7 or D8 would not be a checkmate. Can you figure out why in each case? The reasons are different.


Definitely a checkmate. Must’ve been a computer glitch or maybe it was asking something else. Maybe was asking for a stalemate. Or it asked if you could stretch it out to 3 moves. Just to stretch it out as an exercise. Rather than mate in one.


The highlighted "Qc8#" in your screenshot means, I think, that the displayed move is not the one you made but Qc8# (which means that the queen moves to the c8 square, effecting checkmate). You probably made a different move which is not shown in your screenshot.


Yes, I have used Chess24 once, and it does have some problems. On Chess24 lessons, it has only one fixed solution, where there are many equally good lines.

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