Crafty 25.6.1 (UCI)

UCI-capable Crafty built on upstream Crafty 25.6 — the classic engine by Dr. Robert Hyatt, usable directly in modern GUIs (Arena, Cute Chess, Nibbler, BanksiaGUI, ChessBase, …) alongside its original WinBoard/xboard and native console interfaces (auto-detected from the first command).

This is the 25.6 successor to the 25.2-based v25.2.1 UCI release — the entire UCI conversion re-applied on the newer Crafty 25.6 engine base.

Downloads — pick by your CPU

File	Tier	Requires
crafty-25.6.1-win-x86-64-v3.exe	Cutting-edge (fastest)	AVX2 / BMI2 — Intel Haswell (2013+) / AMD Zen
crafty-25.6.1-win-x86-64-v2.exe	In-between	SSE4.2 / popcnt (2008+)
crafty-25.6.1-win-x86-64.exe	Basic / max compatibility	any 64-bit x86 CPU

All are 64-bit Windows builds compiled with -O3 + profile-guided optimization (PGO), with Syzygy tablebase support and multi-threading (up to 64 threads). If unsure, try v3 first; if it won't launch, fall back to v2, then the basic build.

Highlights

• Now based on upstream Crafty 25.6 (the previous UCI release was 25.2) — the newer search/evaluation from Bob Hyatt, with the UCI layer re-applied on top.
• Full UCI protocol: position, go (depth / movetime / clock / infinite / ponder), stop, ponderhit, streaming info (incl. seldepth and currmove/currmovenumber), bestmove, and options: Hash, Threads, Ponder, SyzygyPath, OwnBook/BookFile, Move Overhead.
• WinBoard/xboard and native console interfaces unchanged — every UCI change is additive and mode-gated.

Notes

• Crafty is © Robert M. Hyatt — free for personal use (see README and the source header); not OSI-licensed.
• 32-bit x86 build not included.
• Reproducible from source via scripts/build-releases.sh. Building Crafty 25.6 on gcc 14+ / clang requires -std=gnu17 (its bundled Syzygy code predates the C23 bool keyword) — already set in the build script, Makefile, and README commands.
• Validated with the UCI transcript test suite (57 assertions) and perft (move-generation) checks.

Crafty 25.2.1 (UCI)

First UCI-capable release of Crafty — the classic engine by Dr. Robert Hyatt, now usable directly in modern GUIs (Arena, Cute Chess, Nibbler, BanksiaGUI, ChessBase, …) alongside its original WinBoard/xboard and native console interfaces (auto-detected from the first command).

Downloads — pick by your CPU

File	Tier	Requires
crafty-25.2.1-win-x86-64-v3.exe	Cutting-edge (fastest)	AVX2 / BMI2 — Intel Haswell (2013+) / AMD Zen
crafty-25.2.1-win-x86-64-v2.exe	In-between	SSE4.2 / popcnt (2008+)
crafty-25.2.1-win-x86-64.exe	Basic / max compatibility	any 64-bit x86 CPU

All are 64-bit Windows builds compiled with -O3 + profile-guided optimization (PGO), with Syzygy tablebase support and multi-threading (up to 64 threads). If unsure, try v3 first; if it won't launch, fall back to v2, then the basic build.

Additional builds — Windows, Linux & Android (by Jim Ablett)

Highly-optimized Windows, Linux, and Android binaries kindly contributed by Jim Ablett. These are marked _ja_ in the filename, and the engine reports its id as Crafty 25.2.1 JA:

• Windows (64-bit): crafty_2521_64_ja_avx512, …_avx2_zen2, …_avx, …_sse4, …_sse3_nopop (no-popcnt fallback)
• Linux (64-bit): crafty_2521_64_ja_avx512_linux, …_avx2_zen2_linux, …_avx_linux, …_sse4_linux
• Android: crafty_2521_ja_aarch64, …_aarch64_dotprod (64-bit ARM), …_armv7a (32-bit ARM)

Pick the highest instruction-set tier your CPU supports, and drop down a tier if a binary won't launch. The Android builds are confirmed working in Droidfish and Chess for Android.

Many thanks to Jim Ablett for contributing these Windows, Linux, and Android builds.

Highlights

• Full UCI protocol: position, go (depth / movetime / clock / infinite / ponder), stop, ponderhit, streaming info (incl. seldepth and currmove/currmovenumber), bestmove, and options: Hash, Threads, Ponder, SyzygyPath, OwnBook/BookFile, Move Overhead.
• Clean info output: one PV line per depth (no duplicate end-of-iteration copy).
• UCI time-management & robustness fixes: correct ponder default, 50-move tracking from a FEN, well-behaved go infinite/ponder bestmove timing, and a volatile cross-thread stop flag.
• WinBoard/xboard and native console interfaces unchanged.

Notes

• Crafty is © Robert M. Hyatt — free for personal use (see README and the source header); not OSI-licensed.
• 32-bit x86 build not included (Jim Ablett's armv7a covers 32-bit ARM).
• Reproducible from source via scripts/build-releases.sh.