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I have a few questions about engine use detection at online games on chess.com:

  1. Let's say both players are rated 1800 on chess.com online play and they make n number of moves in a game.

    White has 90% accuracy due to very decent moves, while black has an accuracy of 97.5%.

    If n > 20 (less likely to be good moves by fluke), does this accuracy score mean that black cheated?

    From my understanding the accuracy also depends on the number of moves made. For example, if you only made 3 moves and followed a well known opening your score will be 100% and that is not suspicious.

    Thus, at what n does the accuracy start to matter when it comes to detecting a cheat?

  2. Chess.com seems to not act upon reports of cheating players.

    Does this mean that those players did not cheat?

    How to escalate the situation to avoid losing those valuable games?

    For example, some players cheat in crucial games in tournaments where a win allows them to advance over you.

  3. What stops someone from turning on a chess engine, when they have a losing position, until they gain an advantage (at which point they play without the engine)?

    This seems like it would be impossible to detect as there will be typical moves (normal moves they make) from their previous games, with a few amazing moves sprinkled in.

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    Clearly, how chess.com and Chessbase compute this, are vastly different. On Chessbase, using the Tactical Analysis function, even Carlsen, when playing at standard time controls, only peaks in the 80% range.
    – PhishMaster
    Dec 25, 2019 at 13:23
  • What does "accuracy" even mean? How do you measure the "accuracy" of the first move of a game? And how to do you compare that number (whatever it might be) with a situation where you are in check and only have one legal move?
    – alephzero
    Dec 25, 2019 at 15:29
  • 2
    Tags don't belong in question titles.
    – Bladewood
    Dec 25, 2019 at 20:41
  • Please ake into account that different positions have different levels of difficulty,. You can hit 100% accuracy in certain positions
    – David
    Jan 9, 2020 at 9:40

4 Answers 4

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It depends a lot on the opening and the players. I have played several 'perfect' games when the opening was one I knew and the opponent made less than perfect moves making my choices obvious. I have also played some games with much worse results.

You can NOT conclude anything from one game or even a few games. I was a statistician but this is not an area I have expertise with but I suspect that you may need hundreds or thousands of games to make that accuracy thing meaningful and yet may still have a wide error band on it.

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I'm a 1400-1500 rated blitz player on chess.com. Looking through my archives, I see that just this month I had a 34 move game, at a 3 2 time control, where I was rated at a 97.4% accuracy. And I know I wasn't cheating.

When I look at my recent daily games (where I'm rated higher, around 1900) I see a 46 move game where I was rated at 99%.

You can't tell anything from a single game.

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  • Can you share your 46 move game? 99% is incredibly hard to get - even top GMs don’t get that high. The only logical conclusion I can make without seeing the game is that your opponent made lackluster moves and you basically forced the position.
    – lbragile
    Mar 17, 2021 at 6:17
  • @Ibragile True, I was winning fairly early on. 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d3 Ng4 6. Bxf7+ Kxf7 7. Ng5+ Kg8 8. Qxg4 d5 9. Qf3 Qf8 10. exd5 Qxf3 11. Nxf3 Bg4 12. dxc6 Bxf3 13. gxf3 h6 14. cxb7 Rb8 15. Be3 Bxe3 16. fxe3 Rxb7 17. b3 c5 18. Ke2 a6 19. Nd2 g5 20. Ne4 Rb6 21. Nxc5 Kf7 22. Nd7 Re6 23. Nc5 Rc6 24. b4 a5 25. a3 Rb8 26. Nd7 Rd8 27. Nxe5+ Ke6 28. Nxc6 Rg8 29. Nxa5 Rc8 30. c4 h5 31. h3 Kd6 32. d4 h4 33. e4 Rf8 34. c5+ Kc7 35. Ke3 Rf4 36. Rhg1 Rf7 37. Rxg5 Rh7 38. d5 Kd7 39. f4 Ke7 40. e5 Kf7 41. Ke4 Ke7 42. Rag1 Kf7 43. f5 Ke7 44. d6+ Kd7 45. e6+ Kc8 46. Rg8# 1-0
    – D M
    Mar 17, 2021 at 9:13
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Im only 1000 in blitz and get 90 - 95 games at least 5 times each day, no it doesn't mean someone is cheating, grandmasters get high nineties every single game.

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We can't determine a cheater from just an accuracy analysis. Perhaps the player was simply good, or most of the moves were forced, leading to high accuracy. However, for an average player to get 99% accuracy, this clearly is a warning.

There is a better approach to detect cheating. A game can be analysed to see how 'computer-like' the moves are. If a person did not use an engine, then it can be clearly seen that he/she is not cheating. However, if an engine was used, then cheating is evident.

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