Chess engine

A chess engine receives a position, examines many legal sequences, and ranks moves by the result it calculates. The engine does the calculation; the graphical user interface displays the board, accepts the user's moves, and presents the analysis. By itself, the engine does not explain the plan in words.

Reading the score

An evaluation is the engine's numerical estimate of which side is better. Many interfaces show a positive value when White is favored, a negative value when Black is favored, and a value near 0 when the position appears balanced. The convention can vary between tools.

A centipawn is one hundredth of the traditional scale: 100 centipawns equal one unit called a pawn. In modern engines, that does not necessarily mean an extra pawn exists on the board. The number estimates the position; it does not count pieces.

What the search data shows

• Depth indicates how far the search has progressed. A larger number usually reflects more calculation, but it does not mean that every option was examined for exactly the same number of moves.
• The principal variation, or PV, is the sequence the engine considers best if both sides choose its preferred replies. Its moves are not necessarily forced.

Why the best move may be hard to play

The best move may work only after several precise replies. It may also be a quiet move, with no capture or check, or a sacrifice, which deliberately gives up a piece or pawn for a later benefit.

The analysis can change with more time, a different engine version, or different settings. The recommendation does not explain by itself how to play the position.