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GNU Chess

GNU Chess 6.0.0 running with the XBoard front end, v. 4.1.5.
Developer(s) GNU project
Stable release 6.2.1 / January 5, 2015
Operating system GNU/Linux, Unix, Mac OS X, Windows
Type Computer chess
License GPL v3 or later

GNU Chess is a free software chess engine which plays a full game of chess against a human being or other computer program. The goal of GNU Chess is to serve as a basis for research. It has been used in numerous research contexts.

GNU Chess is free software, licensed under the terms of the GNU General Public License version 3 or any later version, and is maintained by collaborating developers. As one of the earliest computer chess programs with full source code available, it is one of the oldest for Unix-based systems and has since been ported to many other platforms.


The IQ6 test suite indicates that on basic computer architecture such as an Intel Core 2 Duo CPU, without parallel processing, GNU Chess performs at the senior master/weak international master strength of 2500+ on the Elo rating system.

It is often used in conjunction with a GUI program such as XBoard or glChess, where it is included as the default engine. Initial versions of XBoard's Chess Engine Communication Protocol were based on GNU Chess's command line interface. Version 6 also supports the Universal Chess Interface (UCI).


The first version of GNU Chess was written by Stuart Cracraft. Having started in 1984 in collaboration with Richard Stallman prior to his founding of the GNU project, GNU Chess became one of the first parts of GNU.

GNU Chess has been enhanced and expanded by dozens of programmers. Versions from 2 to 4 were written by John Stanback. Version 5 was written by Chua Kong-Sian. Version 6 was written by Fabien Letouzey.

In 2011, GNU Chess transitioned to version 6, which is based on Letouzey's Fruit 2.1 chess engine. Some GNU Chess enthusiasts have continued to maintain the 5.07 code base. According to CEGT version 5.60 of this code base is stronger than Fruit 2.3.

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