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How are moves classified? What is a ‘blunder’ or ‘brilliant’ and etc?
How are moves classified? What is a ‘blunder’ or ‘brilliant’ and etc?
Updated over a week ago

The improved Move Classification system provides a tailored Game Review experience: The new Brilliant and Great Move categories highlight key moments, while the Expected Points formula pinpoints mistakes that matter most for your improvement.

After each game, you'll see a list of all your moves in the game review, classified as Best or Inaccuracy, or any other such classifications. How are these determined?

Expected points model

Expected Points employs data science to calculate a player's probability of winning by considering their rating and the engine's evaluation of the position.

Classifying moves in chess involves both art and science. How do we distinguish between a good move and an inaccurate one? How do we define a blunder for a chess master versus a new player? Is it more significant to go from +2 to +1 or from +0.7 to +0? What engine evaluation makes a position winning?

With Classification V2, has adopted an Expected Points model to answer these questions.

Expected Points uses data science to determine a player’s winning chances based on their rating and the engine evaluation, where 1.00 is always winning, 0.00 is always losing, and 0.50 is even.

At 1.00, you have a 100% chance of winning, and at 0.00, you have a 0% chance of winning. After you make a move, we evaluate how your expected points—likely game outcome—have changed and classify the move accordingly.

The table below shows the expected points cutoffs for various move classifications. If the expected points lost by a move is between a set of upper and lower limits, then the corresponding classification is used:


Lower Limit

Upper Limit



















Special move classifications beyond expected points

Special move classifications that use rules beyond expected points have also undergone improvements.

This includes familiar classifications like Missed Win and Brilliant, as well as the new Great Move classification:


When is it used?

Missed Win

A Missed Win is when you fail to capitalize on your opponent's mistake and miss the opportunity to gain a winning position, often resulting in an equal or worse outcome.

The engine evaluation required to determine a winning, equal, or losing position varies according to the player's rating, similar to expected points.


Brilliant Moves are always the best or nearly best move in the position, but they are also special in some way.

We replaced the old Brilliant algorithm with a simpler definition: a Brilliant move is when you find a good piece sacrifice.

There are additional conditions:

  • You should not be in a bad position after a Brilliant move

  • You should not be completely winning even if you hadn't found the move.

We are also more generous in defining a piece sacrifice for newer players compared to those who are higher-rated.

Great Move

These are moves that were critical to the outcome of the game, such as turning a losing position into an equal one, an equal position into a winning one, or finding the only good move in a position.

Similar to Brilliant Moves, we are more generous in what we call a Great Move for new players compared to higher-rated players.

Check out this article to learn more about Game Review: How does Game Review work?

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