The Baron is a strong chess engine written by Richard Pijl.

December 30th 2018: Release of Version 3.44

Bugs solved:

  • Syzygy probing when using an incomplete 6-men (or complete 5-men) set was buggy
  • Additional error with Syzygy probing solved (probably affects all Syzygy configurations)
  • Fixed problem with Syzygy DTZ probing (caused Baron to refuse to move sometimes)
  • Updated baron.ini to reflect the default options correctly
  • Fixed minor SMP bug
  • Pin detection in evaluation only detected close pins.
  • Handle spaces in the syzygy path
  • Slightly more restrictive in playing easy moves
  • Fixed singular extensions bug
  • Increased search stack size
  • Chess960 bug fixed in 3.441 version


  • Use more time for first moves after leaving book
  • Set thinking time after checking for book moves (in internal books).
  • Minor evaluation improvements (Knight vs Bishop)
  • Evaluation tuning
  • Detecting pins to the queen
  • Evaluation tuning
  • Better use of time, especially on short time controls
  • More selective in quiescent search
  • Reduced aspiration window



January 8th 2018: Release of Version 3.42

This will be the last release of The Baron 3.x code base. Richard has already started working on The Baron 4.0. Here are the main changes with this release:

  • Improved Syzygy support
  • Used a better compiler giving a slightly faster executable
  • Includes a 32-bits windows executable, a 64-bits Numa executable and a raspberry pi version



October 22nd 2017: Release of Version 3.41 (Dated May 2017)

Richard has released the latest version of The Baron. He’s about to embark on a re-write, so decided to release the final version of this generation of The Baron. You can find the many changes in the “release.txt” file included in the download. This version is definitely stronger than v3.29 but Richard isn’t clear exactly how much of an improvement he’s made.



July 7th 2015: Release of Version 3.29 (Dated Feb 26th 2012)

  • The bitbases mentioned in the configuration file is the own Baron format, which I replaced already with the Syzygy ones in newer versions of the Baron. These bitbases are therefore not available
  • No native books available for the Baron.
  • Native CTG support is there, but it mainly responds on annotation symbols in the book (!!, ! and ?). As the scoring method of Chessbase has not been described yet, there will be differences in moves that will be played by ctg-books based on game statistics between the Baron and Chessbase GUIs.
  • The Baron supports both UCI2 and Winboard2 and can also be used from the console (using winboard style commands).

Bugs solved:

  • 50-move draw bug fixed
  • SMP bug fixed that caused aborting searching plies, resulting in the display of erroneous drawscores
  • A buffer overflow in the internal epd test suite code is fixed
  • FRC/Chess960 support is fixed


  • New defaults for several parameters are chosen, most of them based on the work by Rodolfo Leoni. These are reflected
    by the attached sample baron.ini file. Among those that are impacted:
  • This makes the learning file incompatible with previous versions. The name is changed to ‘baron.plf’
  • The length of the zobrist key in the learning file is increased from 64 to 128 bits
  • The two learning options are now replaced by a single new one: learning. It can be turned on or off.
  • Redesigned the Position Learning code as part of the ongoing rewrite.
  • Rewritten Hashkey handling in the hashtable. More bits are now available to prevent hashkey collissions
    • nullbase (now 10)
    • nullprogress (now 8)
    • singmargin (still 100, but internally the values were changed, comparable to the old 40)
    • splitdepth (now 12)
  • The recommendation is still to leave everything commented out unless you know what you’re doing. Default may change in a future release again
  • Changed scoring weights of the Baron’s own book format. Not relevant for other book formats
  • Multi-PV mode is more stable (i.e. moves remain in the same order unless the score changes)