# chess.com Analysis “Accuracy” - What score is computer like for a given rating?

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.

• 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 '19 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 '19 at 15:29
• Tags don't belong in question titles. – Bladewood Dec 25 '19 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 at 9:40

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.

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.

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.

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.