Stockfish analysis

Stockfish is an open-source chess engine, considered one of the strongest in the world. Its development began in 2008 and has been continuously improved by a community of developers. Unlike commercial programs, Stockfish is free and its code is publicly available, allowing tools like Nexa chess to integrate it and offer high-quality analysis at no cost to the user.

The engine evaluates positions by assigning a numerical value that indicates who has the advantage and by how much. A value of +1.5, for example, means white has an advantage equivalent to roughly one and a half pawns. Values close to zero indicate equality, while extreme evaluations (like +10 or −10) usually signal positions where one side has a decisive advantage or is about to deliver checkmate.

After importing your games from Lichess or Chess.com, the Nexa chess analysis server processes each game with Stockfish. The engine examines positions move by move, calculating the evaluation at each point and comparing it with the previous move. When it detects a sharp swing in evaluation, it marks that moment as critical.

For example, if the evaluation goes from +0.3 to −2.0 after your move, the engine understands you made a significant mistake. Nexa chess classifies these errors by severity: inaccuracies (minor loss), mistakes (moderate loss), and blunders (major loss, often a piece or winning position).

For each critical position, the analysis shows the move you played versus the best move according to Stockfish. This way you understand not only that you made a mistake, but what specific alternative made more sense and why the evaluation changed.

Analysis depth refers to how many moves ahead the engine calculates before giving its evaluation. Greater depth means greater accuracy, but also longer calculation time. Nexa chess uses an optimized depth that balances precision and speed, sufficient to detect tactical errors and correctly evaluate most positions that appear in games by amateur and club players.

For most players, what matters is not maximum depth, but being able to see patterns in their mistakes. If you repeat the same type of error week after week—for example, leaving pieces unprotected in the middlegame or miscalculating pawn endgames—the accumulated analysis will show it clearly.

Nexa chess not only analyzes the complete game, but separates results by opening, middlegame, and endgame. This division lets you identify in which phase you tend to lose advantage. Perhaps your openings are solid but you make systematic mistakes in endgames, or vice versa.

This breakdown combines with weekly tracking: you can see if your endgame performance has improved in recent weeks or if you keep making the same mistakes. The key is to turn analysis into a study plan: if the engine detects recurring errors in rook endgames, that is the topic you should practice.

The goal of Stockfish analysis is not only to look at evaluation bars: it is to spot patterns. A single bad game does not say much, but if the same types of errors appear in ten, twenty, or fifty games, you have valuable information about what you need to train.

Combine move-by-move analysis with weekly tracking and the opening breakdown to turn every review into a concrete plan. If you detect that your errors concentrate in certain openings, you can study those lines. If the middlegame is your weak point, you can practice tactics and calculation. If endgames cost you, there are specific resources to improve that phase.

Nexa chess gives you the data; the work of improving is up to you, but at least you know exactly where to focus your effort.