Mantissa is a young UCI-compatible chess engine written as a side project to learn both chess programming and also rust. Because of this, there are many things to improve both in terms of code organization and in terms of performance and correctness for Mantissa, but there are a lot of ideas packed in already.

ReleasesHomeInfo • Rust • UCI • Jeremy Wright (USA)

A UCI compatible chess AI written in Go.

ReleasesHomeHomeInfo • Go • UCI • Amanj Sherwany (Iraq)

RubiChess development started in 2016 as a private hobby project to practise programming in C++ and to see the engine improving compared to earlier releases. Meanwhile some years later RubiChess got pretty competitive and is listed in most of the rankings and plays a lot of even big tournaments.

ReleasesHomeInfo • C++ • UCI • Andreas Matthies (Germany)

Seer is an original, strong UCI chess engine. Seer relies on a neural network estimating WDL probabilities for position evaluation.

ReleasesHomeInfo • C/C++ • UCI • Connor McMonigle (USA)


A chess engine written in C++ designed to fit into 4,096 bytes. There are two versions of the engine: 4ku, and 4ku-mini.

4ku and 4ku-mini should be identical in terms of their play, but 4ku’s info strings mean it is probably slightly slower and slightly weaker.

DownloadHomeLichess Bot • C++ • UCI • Robert Taylor (England), Gediminas Masaitis (Lithuania), Gian-Carlo Pascutto (Belgium)

UCI Info

4ku 1.0

id name 4ku
id author kz04px
option name Threads type spin default 1 min 1 max 256
option name Hash type spin default 64 min 1 max 65536

4ku 1.1

id name 4ku
id author kz04px
option name Threads type spin default 1 min 1 max 256
option name Hash type spin default 64 min 1 max 65536

4ku 2.0

id name 4ku 2.0
id author kz04px
option name Threads type spin default 1 min 1 max 256
option name Hash type spin default 64 min 1 max 65536

A chess engine by Dominique Longbien, written in C++, and first released in June 2002 as WinBoard engine. Adam 3.3, released in March 2011, is compatible with UCI only.

Info • C++ • XB/UCI • Dominique Longbien (France)

A Chess Engine Communication Protocol compliant open source chess engine under the GPL by Juan Benitez, written in C, with appropriate compiles able to run under Windows, Linux, Mac OS and Android platforms. Betsabe II is successor of Betsabe, which already played various Spanish Computer Chess Championships in the 90s, notably the SCCC 1993 where it became first Spanish Champion with a 100% score, and the SCCC 1994 as runner-up behind Zeus II.

Info • C • XB/UCI • Juan Benitez (Spain)

The Ceres MCTS engine is a novel implementation written in C# for the Microsoft .NET framework. This system comprises about 80,000 lines of source in 500 source code files, developed as a way to try to make something good come of COVID confinement. The underlying neural networks (and backend code to execute them) and backend code are currently mostly borrowed from the LeelaChessZero project via a “plug-in” architecture.

ReleasesHomeInfo • C# • UCI • David J. Elliott

A Chess Engine Communication Protocol compatible, free chess engine by Philipp Claßen, written in C++.

DownloadInfo • C++ • XB • Philipp Claßen (Germany)

Blue Marlin is a Stockfish-derivative chess engine created by “dorsz” that is focused on king attack and sacrifices. This engine has two book slots in which you can load any .bin book you need.

Download • C++ • UCI • Stockfish-derivative

C++ • UCI • Ivan Maklyakov (Russia)

A UCI compliant chess engine by Álvaro Begué and José Manuel Morán, written in C++, developed since 2013 and first published as open source under the MIT License in June 2017.

DownloadInfo • C++ • UCI • Álvaro Begué (Spain), José Manuel Morán (Spain)

Black Marlin is a UCI compliant chess engine fully written in Rust by Doruk Sekercioglu.

ReleasesHomeInfo • Rust • UCI • Doruk Sekercioglu (Turkey)

Allie is a chess engine heavily inspired by the seminal AlphaZero paper and the Lc0 project.

Like Leela, Allie is based off of the same concepts and algorithms that were introduced by Deepmind in the AlphaZero paper(s), but her code is original and contains an alternative implementation of those ideas. You can think of Allie as a young cousin of Leela that utilizes the same networks produced by the Lc0 project.

ReleasesHomeInfo • C/C++ • UCI • Adam Treat (USA)

Arasan is a chess engine, that is, a console-based program that plays the game of chess.

For communicating with a chess interface, Arasan supports either the standard CECP protocol (version 2) or the UCI protocol. CECP is the native protocol used by Winboard and xboard. UCI-compatible chess interfaces include ChessBase and Fritz. Arena, a free interface, supports both protocols.

Arasan is multi-platform (Windows, Linux, Mac OS, Unix) and supports multi-threading for higher performance.

DownloadReleasesHomeInfo • C++ • UCI • Jon Dart (USA)

Rofchade is a UCI chess engine written in C++ by Ronald Friederich.

ReleasesDownloadHomeInfo • C++ • UCI • Ronald Friederich (Netherlands)

A strong UCI (no NNUE) chess engine utilizing a hand-crafted evaluation function.

ReleasesReleasesHomeHomeInfo • C++ • UCI • Norman Schmidt (USA)

A UCI chess engine developed by Belgian programmer Robert Houdart. It is influenced by open-source engines IPPOLIT/RobboLito, Stockfish, and Crafty. Versions up to 1.5a are available for non-commercial use, while 2.0 and later are commercial only.

SourceHomeInfo • C++ • UCI • Robert Houdart (Belgium)

Sjeng is a chess engine written by Gian-Carlo Pascutto based on Faile, written by Adrien Regimbald. There are two major versions of Sjeng: the original open source version called Sjeng (also now known as Sjeng old or Sjeng free) and Deep Sjeng, a closed source commercial version.

DownloadHomeInfo • C • XB/UCI • Gian-Carlo Pascutto (Belgium)

A free and open source UCI chess engine written in Rust.

ReleasesHome • Rust • UCI • Cristopher (Sweden)

Komodo started in 2007 as a joint project by programmer Don Dailey and grandmaster Larry Kaufman when he was a member of the team that created Rybka 3, then the world’s strongest chess engine.

ReleasesHome • C/C++ • UCI • Don Dailey (USA), Larry Kaufman (USA), Mark Lefler (USA)

Dragon uses NNUE (Neural Network Updated Efficiently) technology, originally developed for the game of shogi. Komodo has a great deal of chess knowledge in its evaluation. Training an NNUE network based on this evaluation was both an advantage and a challenge, requiring experimentation with architectures and data generation of billions of positions.

ReleasesHome • C++ • UCI • Larry Kaufman (USA), Mark Lefler (USA)

BlackCore is a neural network based chess engine developed from scratch. Its alpha beta search uses various pruning techniques, powered by blazing fast move generator.

ReleasesHome • C/C++ • UCI • Balazs Szilagyi (Hungary)

Bagatur chess engine is one of the strongest Java chess engines in the world.

ReleasesHome • Java • UCI • Krasimir Topchiyski (Bulgaria)