Welcome to the Houdini Chess Engine home page. Houdini is a state-of-the-art chess engine for Windows, the current version Houdini 1.5a is widely considered to be the strongest chess engine on the planet.

Houdini is free for non-commercial use. It can be downloaded, installed and freely used for playing chess games and analysis of chess positions without commercial purpose.

The name Houdini was chosen because of the engine's positionaly style, its tenacity in difficult positions and its ability to defend stubbornly and escape with a draw – sometimes by the narrowest of margins. On the other hand Houdini will often use razor-sharp tactics to deny its opponents escape routes when it has the better position.

As of December 17, 2010, Houdini 1.5 was ranked #1 on the leading IPON computer chess rating list, 50 Elo ahead of Rybka 4 and 100 Elo ahead of Stockfish 1.9 and Critter 0.9.

Houdini is appreciated by many players and even top Grand Masters. In a recent interview, when asked the question "If you had to pick one player to represent earth in a chess game vs. aliens, which active player would it be? You can pick different active players for the white and black side, if you feel it necessary.", super GM Peter Svidler had a simple reply: "Houdini".

You can contact the author of Houdini, Robert Houdart, with suggestions or problem reports at the following e-mail address: houdini@cruxis.be.

If you enjoy Houdini, feel free to donate to the development of Houdini. Donations will be used for purchasing hardware to improve the testing of Houdini and will contribute directly to future versions.

Rybka (4.1) is a UCI chess engine programmed by International Master Vasik Rajlich.

You can download Rybka 2.3.2a for free. Rybka 2.3.2a was the final version of the Rybka 2 series and does give a fairly good introduction to the style and general approach of the engine.

You can also download RybkaII.ctg, the official opening book for Rybka 2 by Jeroen Noomen. Note that this book is much smaller than the official books for later Rybka versions and was created for computer chess only.

Stockfish is an open-source UCI chess engine based on Glaurung. Stockfish is an alpha-beta searcher and uses a bitboard representation.

Rated at over 3200 ELO on most chess rating lists, Stockfish is right up there with commercial engines like Rybka and Naum.

Stockfish is available for Windows, Mac OS X and Linux. Want to do chess analysis on the go? We've got an iPhone/iPad app, too.

Stockfish is free and uses the GPL license. You can download, read, and modify the source code.

Naum is a chess engine supporting both Winboard and UCI protocols, so you can use it with any GUI available.

It has been under continuous development since 2003 and at the moment is one of the top 3 chess engines in the world. You can check the current ranking here CEGT testing group and here CCRL testing group

The first version of Naum was made for the Palm handheld computers. Once I discovered the fiercely competitive PC chess engine community I ported the engine from Palm to the PC platform. The first PC version was very weak. It was losing to Gerbil (my first test partner). Once I started implementing the common chess engine development techniques (transposition tables, null moves, etc.) the playing strength gradually increased and at the end of 2003 Naum was already playing at the level of more established engines like Arasan and Comet. Naum 1.0 was released to the public in April,2004 Since then, Naum is being constantly improved by implementing thousands of new ideas and testing them 24 hours each and every day using at least 2-3 computers. Major improvements also came from the ideas found in many open source engines like Crafty, Fruit and Glaurung, so a big thanks should go to their authors for sharing them.

Fire is both a blessing and a bringer of doom... this is a greatly improved multi-processor (SMP) derivative of the famous IppoLit family of engines, the strongest chess playing programs in the world
Fire 1.31 is available is available for download.

IvanHoe (the most important engine released in the last 5 years: free and open-source!)
IvanHoe version 999947 is available for download.


Rebbolito RobboLito is the world's strongest single processor (non SMP) chess engine. this is the newest version of the October Revolution's world famous and ground breaking program!
RobboLito 0.085g3 is available for download.


cyclone is a very strong open-source UCI chess engine based on Fruit and Toga. Cyclone xTreme StormPack are available for download.



Demon is an open-source UCI chess engine.
Demon 1.0 is available for download.



Toga II is a very strong open-source UCI chess engine.
Toga II 2.0 SE is available for download.

Welcome to HIARCS, a World Championship winning chess software engine available for Pocket PC, Palm, Apple iPhone & iPod Touch, PDAs, PC and Macintosh computers. HIARCS provides the strongest chess software on many platforms and is available direct from the developer and is renowned for its high quality, world class chess strength, handicap levels and features. Unprecedented performance from handheld devices to multi-core/processor desktops.