Slow Chess Blitz, a free chess program

Slow Chess Blitz by Jonathan Kreuzer

Slow Chess is a strong free chess program.

(Full size screenshot)

Download Slow Chess Blitz 2.9:

for Windows (64-bit): SlowChess-2.9.zip 4.5 MB
updated Jul 5, 2022
(note: you should use slow64-avx2 if your computer supports AVX2, it is significantly faster.)

2.9 for Linux (64-bit): SlowChess-Linux-2.9.tar.gz 3.6 MB
(console engine only requires UCI or Winboard GUI)

About 2.5+:

Using Slow Chess : Own GUI or Winboard / UCI
Update History
2.5+ use neural nets for evaluation in all stages of the game. (2.4 had only endgame neural nets.)
slow64-avx.exe is fastest
slow64-sse.exe is for older CPUs that don't support AVX2, it will have slower nps.
(With neural net eval hardware popcount is no longer a measurable speed up, so slow64-sse has no hardware pop also.)

Features:

Strong play. For a detailed estimate check these major ratings lists : CCRL, (FRC), (4-core), CEGT, (25'), FGRL, (10'), SPCC, FCP
Analyze mode to suggest the best move for any position, or moves in multi-variation move
Winboard and UCI support, so you can use it outside its own GUI. more
Multi-threaded search support for all interfaces (defaults off. Search->threads in own GUI)
Chess 960 support in own GUI and UCI mode. (also known as Fischer Random Chess)
Adjustable search options, hash table, pondering.
Difficulty Level by time per move, number of ply, or number of nodes
PGN support for saving / loading games.
Copy / Paste text transcripts, positions
Game transcript box, and take back/ redo move buttons for playback of games.
Player Clocks & set timelimit option.
Dev Menu options : display perft, evaluation, tt-entry, right-click on piece for individual eval, and more

Older Versions :

Download Slow Chess Blitz 2.83:

for Windows (64-bit): SlowChess-2.83.zip 4.5 MB
updated Jan 31, 2022
(note: you should use slow64-avx2 if your computer supports AVX2, it is significantly faster.)

2.83 for Linux (64-bit): SlowChess-Linux-2.83.tar.gz 3.5 MB
(console engine only requires UCI or Winboard GUI)

for Windows (64-bit): SlowChess-2.8.zip 4.5 MB
updated Aug 24, 2021
(note: you should use slow64-avx2 if your computer supports AVX2, it is significantly faster.)

for Linux (64-bit): SlowChess-Linux-2.8.tar.gz 3.5 MB
(console engine only requires UCI or Winboard GUI)

for Windows (64-bit): SlowChess-2.7.zip 4.3 MB
updated Aug 24, 2021
(note: you should use slow64-avx if your computer supports AVX2, it is significantly faster.)

for Linux (64-bit): SlowChess-Linux-2.7.tar.gz 3.4 MB
(console engine only requires UCI or Winboard GUI)

2.6 for Windows (64-bit): SlowChess-2.6.zip 4.4 MB
updated Jul 19, 2021
(note: you should use slow64-avx if your computer supports AVX2, it is significantly faster.)

2.6 for Linux (64-bit): SlowChess-Linux-2.6.tar.gz 3.5 MB
(console engine only requires UCI or Winboard GUI)

2.54 dev version

2.5 for Windows (64-bit): SlowChess-2.5.zip 4.2 MB
updated Jan 17, 2021
(note: you should use slow64-avx if your computer supports AVX2, it is significantly faster.)

2.5 for Linux (64-bit): SlowChess-Linux-2.5.tar.gz 3.0 MB
(console engine only requires UCI or Winboard GUI)

Classic 2.4 for Windows (64-bit): SlowChessClassic-2.4.zip 4 MB Nov 1, 2020
(note: if your CPU doesn't support AVX2, you now should use slow64-noAvx)

Classic 2.41 for Linux (64-bit): SlowClassic-Linux-2.41.tar.gz 3 MB
(note: if your CPU doesn't support AVX2, you now should use slow64-noAvx)

Classic 2.3 for Windows (64-bit): SlowChessClassic-2.3.zip 2.4 MB

Classic 2.2 for Windows (64-bit): SlowChessClassic-2.2.zip 2.4 MB

Classic 2.2 for Linux (64-bit): SlowChessClassic-Linux-2.2.tar.gz 1.5 MB
(console engine only requires UCI or Winboard GUI)

Classic 2.1 for Windows (64-bit): SlowChessClassic-2.1.zip (2.0 MB)

Classic 2.0 for Windows (64-bit): SlowChessClassic-2.0.zip (1.9 MB)

Classic 1.9 for Windows (64-bit): SlowChessClassic-1.9.zip (1.8 MB)

Classic 1.8 for Windows (64-bit): SlowChessClassic-1.8.zip (1.7 MB)

Classic 1.7 for Windows (64-bit): SlowChessClassic-1.7.zip (1.5 MB)

Classic 1.6 for Windows (64-bit): SlowChessClassic-1.6.zip (1.5 MB)

Classic 1.5 for Windows (64-bit): SlowChessClassic-1.5.zip (1.5 MB)

Classic 1.4 for Windows (64-bit): SlowChessClassic-1.4.zip (1.5 MB)

Classic 1.0 for Windows (64-bit): SlowChessClassic-1.0.zip (1.2 MB)

Logos :

Ancient Versions :

Slow Chess Blitz WV2.1 for windows XP/Vista/Me/2000: SlowBlitzWV21.zip ( 584 KB )
Download endgame bitbases, this is optional. (Unzip to the same directory as the .exe): SlowBitbases.zip ( 553 KB )

What's New.txt for Blitz 0.4 - WV2.1 versions

Slow Chess Blitz WV2 : SlowBlitzWV2.zip

Note: Version numbers change with playing style/strength changes. Otherwise the version just gets a newer letter. Read What's New for info on latest updates.
Version History.txt (changes from 2.82 to 2.96)

Slow Chess Blitz WV: SlowBlitzWV.zip ( 541KB )

Slow Chess Blitz 0.4: SlowBlitz0.zip ( 508KB )

Slow Chess 2.94: slow294.zip (498 KB )

Slow Chess 2.89b: schess289.zip (472 KB)

Slow Chess 2.82: schess282.zip (444 KB)

Very Old (and messy) Source Code:

Slow Chess 2.96: Slow296src.zip (86 KB). Details in Readme296.txt
2.96 is an open source 2.94 chess engine (with a few very small changes.) This source code is for the engine only, it does not include the GUI source. So you must run it using winboard or UCI. It compiles with Microsoft Visual C/C++ 6.0. This is a much stronger chess engine than 2.82a, and the code should be clearer too, and without assembly language.
If you want my test compiled .exe, and an opening book, download Slow296.zip (442 KB)
Slow 2.96 and Blitz WV can use the bitbases downloadable above. No other versions use these bitbases, although all others have a different and incompatible KPK.sbb. Books are comptible between all versions.

Slow Chess 2.82a: ChessSource27.zip ( 155 KB). It is compiled in Microsoft Visual C/C++ 6.0. It's mostly in C/C++, but also uses assembly language code for move generation and attack checking. The assembly language code offers almost no speed up compared to recent compilers, but when compared to older compilers (specifically the one I first used to compile Slow Chess 2.0,) it made the movement/attack code 2 or 3 times faster. Some code isn't currently used, like the see.cpp and a few various functions that I started but didn't finish.

Go to 3dkingdoms.com and check out other programs.

Mail me. *IMPORTANT NOTE* My email for this web page was completely overrun by automated spam. I'm still deciding if I want to set up another email / try to fix it.