What is 'accuracy' in analysis? How is it measured?

At the end of a game after you run the analysis and look at the game report, you will see a score out of 100 for your accuracy that game. What does this mean? 

Your 'accuracy' is a measurement of how closely you played to what the computer has determined to be the best possible play against your opponent's specific moves. The closer you are to 100, the closer you are to 'perfect' play, as determined by the engine. 

'Accuracy' uses a statistical model to gather all of the player's moves together and then boil those down into a single number.  A bad blunder can drag the number down, and a brilliant move, or a lot of exact moves will bring it up. So this score is not necessarily a 1 for 1 match with the percentage of moves that match what the computer would have played. 

90% of the time, overall Accuracy predicts the winner, but 10% of the time, we see that there is more to chess than just Accuracy! This is in part because accuracy is less sensitive to blunders than the actual game result is! You could have a very high accuracy, but still lose, because it only takes one blunder to lose the game! 

It is important to note that high CAPS is not any signifier of cheating, and in fact plays no part in the cheat detection process! You can learn more about CAPS from IM Danny Rensch in this video:

GMs regularly get accuracy in the high 90's. But beginners can get accuracy of this level too! Because all it takes is playing the best response to your opponents moves, at beginner levels, the best response can often be easy to see. 
What's your best accuracy? 
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