Syzygy tablebases

An endgame tablebase stores the result of every legal position within a small material set. Instead of estimating the position through search, software looks up a precomputed answer. Syzygy covers endgames with up to seven pieces including both kings, although positions with castling rights are not part of the standard tables.

WDL and DTZ

Syzygy separates its main information into two file types. WDL means win, draw, loss under perfect play, with information related to the fifty-move rule. DTZ means distance to zeroing: the distance to a move that resets that rule's counter, namely a capture or a pawn move.

Together they let an engine preserve a win or draw without ignoring the risk of fifty moves by each side passing without a capture or pawn move. This does not mean that Syzygy always selects the shortest mate. Its main metric seeks to preserve the result and reach a counter-resetting move in time.

The tables are exact within their coverage, but they cannot answer positions with more pieces and do not replace endgame understanding. They also need the correct halfmove clock, because the same board can be a win or a draw depending on how far the fifty-move count has progressed.

Gaviota and Nalimov are other tablebase families. Both are primarily associated with distance-to-mate data, while Syzygy is known for WDL, DTZ, and broad integration in modern engines.