Stockfish 13

It is our pleasure to release Stockfish 13 to chess fans worldwide. As usual, downloads are freely available at

The Stockfish project builds on a thriving community of enthusiasts who contribute their expertise, time, and resources to build a free and open-source chess engine that is robust, widely available, and very strong. We would like to thank them all!

The good news first: from now on, our users can expect more frequent high-quality releases of Stockfish! Sadly, this decision has been triggered by the start of sales of the Fat Fritz 2 engine by ChessBase, which is a copy of a very recent development version of Stockfish with minor modifications. We refer to our statement on Fat Fritz 2 and a community blog for further information.

This version of Stockfish is significantly stronger than any of its predecessors. Stockfish 13 outperforms Stockfish 12 by at least 35 Elo. When playing against a one-year-old Stockfish, it wins 60 times more game pairs than it loses. This release features an NNUE network retrained on billions of positions, much faster network evaluation code, and significantly improved search heuristics, as well as additional evaluation tweaks. In the course of its development, this version has won the superfinals of the TCEC Season 19 and TCEC Season 20.

Going forward, the Leela Chess Zero and Stockfish teams will join forces to demonstrate our commitment to open source chess engines and training tools, and open data. We are convinced that our free and open-source chess engines serve the chess community very well.

Stay safe and enjoy chess!

The Stockfish team