official-stockfish/stockfish

Stockfish is a free chess engine, a program that analyzes chess positions and computes the best possible moves. It is derived from an earlier engine called Glaurung 2.1. The term "UCI" in its description stands for Universal Chess Interface, a standard protocol that allows chess engines to communicate with graphical frontends (the visual boards where you can move pieces). Stockfish itself does not include any visual interface; you pair it with a separate GUI application of your choice to see the board and play. Under the hood, Stockfish uses neural networks for position evaluation. These networks were trained on data provided by the Leela Chess Zero project. The neural network data is stored in a file with the .nnue extension, which in binary releases is embedded directly into the program. The engine supports 32-bit and 64-bit CPUs and can be compiled on Unix-like systems using the included Makefile. It is written in C++ and is released under the GNU General Public License version 3 (GPL v3), which means you can use, share, and modify it freely as long as you also distribute the source code and keep it under the same license. Engine testing and improvement happens through a community platform called Fishtest, where contributors can donate their computer hardware to help run testing of potential improvements to the engine's playing strength. Discussions and development coordination take place on the project's Discord server.