Syzygy tablebases are exhaustively computed databases that contain the game-theoretic value (win, draw, or loss) and distance to mate or conversion for every legal chess position with up to 7 pieces on the board. syzygy-tables.info provides a free web interface to query these tablebases without needing to download the multi-terabyte files locally.

Enter any position via FEN or navigate from the starting position, and the site instantly shows which moves win, draw, or lose with perfect play, along with the distance to zeroing move (capture or pawn push) and eventual mate. This is particularly useful for studying endgame technique, verifying fortress positions, or understanding why certain endgames are theoretically drawn despite looking difficult.

The Syzygy tablebase format was created by Ronald de Man and extended by Bojun Guo. The complete 7-piece tablebases require around 18 TB of storage; the web interface lets anyone access this data for free. The tablebases themselves can also be downloaded and used locally with compatible chess engines including Stockfish.