64Logic

A complete chess engine in just 1,953 characters of C source code, by H.G. Muller. Play it here, then get our free UCI edition on GitHub.

Get it on GitHub
micro-Max 4.8

    Loading micro-Max…

    You White

    1,953 characters, unchanged

    micro-Max is a chess program by H.G. Muller, written to see how much real chess fits in the smallest possible C source code. Version 4.8 plays complete games, including castling, en passant, and repetition draws, with a genuine search and evaluation:

    • Negamax search with iterative deepening
    • Quiescence search over all captures, best captures first
    • A hash table that keeps scores and best moves
    • Null-move pruning, futility pruning, and late-move reductions
    • King safety, plus pawns valued more as they advance

    Muller released version 4.8 two ways: as a stand-alone program you play by typing moves at a text prompt, and as a version for the WinBoard chess program on Windows, with the engine’s code changed to fit WinBoard.

    micro-Max 4.8 UCI adds the Universal Chess Interface to the original engine without changing it. Muller’s umax4_8.c is compiled exactly as published, byte for byte, with a separate 64Logic integration layer, and every build checks the SHA-256 of umax4_8.c before compiling.

    The engine on the board above is built from the same umax4_8.c, compiled to WebAssembly so it runs entirely in your browser. Your moves are never sent to a server. Move for move, it matches micro-Max 4.8 UCI (Core) on Linux, down to the node count.

    Here micro-Max plays the way Core does: every game starts from the opening position, it thinks until its own search finishes, usually a few seconds, and pawns always promote to a queen.

    Don’t underestimate this small engine: most chess players will find it hard to beat.

    umax4_8.c Checking SHA-256… 
    Loading the source…

    SHA-256 447cd24da6275221a1e9564d9282cb69f019b6c521dde1f063b9eb7de3fd34eb

    Two editions, one engine

    Both run Muller’s umax4_8.c, unchanged, with a separate 64Logic integration layer. Core keeps micro-Max exactly as designed. The full edition adds the UCI features the original engine doesn’t support.

    micro-Max 4.8 UCI Core

    Available now, v1.0

    The preservation edition, ready for UCI chess programs.

    • Muller’s umax4_8.c, byte for byte
    • Plays from the standard starting position
    • Position setup from FEN
    • Time management
    • Search limits: depth, nodes, and move time
    • Interrupting a search, continuous analysis, and true pondering

    Frozen at v1.0. Future changes are limited to correctness, portability, and documentation.

    Download Core

    micro-Max 4.8 UCI

    In development

    The full UCI edition. The same unchanged engine, being built for complete UCI support: timed matches, set positions, and analysis.

    • Muller’s umax4_8.c, byte for byte
    • Plays from the standard starting position
    • Position setup from FEN
    • Time management
    • Search limits: depth, nodes, and move time
    • Interrupting a search, continuous analysis, and true pondering

    Builds and source code will be published on GitHub in a separate repository.

    Follow 64Logic on GitHub

    Download

    Run micro-Max 4.8 in Cute Chess, Shredder, HIARCS Chess Explorer, or other programs that speak UCI. Each build is a single small executable with no installer.

    micro-Max 4.8 UCI Core v1.0

    macOS

    Apple siliconarm64, 10.6 KB Intelx86_64, 9.5 KB

    The binaries are unsigned. If macOS blocks the engine the first time, allow it in System Settings › Privacy & Security.

    Windows

    x64x86_64, 18.7 KB ARMarm64, 75.5 KB

    Linux

    x64x86_64, 11.1 KB ARMarm64, 12 KB

    FreeBSD

    x64x86_64, 11.9 KB

    Verify downloads against SHA256SUMS.txt, or see all Core releases.

    micro-Max 4.8 UCI

    In development. Builds will appear here when it’s released.

    Build Core yourself

    Two C files and a Makefile. Builds with Apple’s Command Line Tools on macOS, GCC or Clang on Linux and FreeBSD, and MSYS2 UCRT64 on Windows x86-64. Windows ARM64 needs Clang; see the README.

    View the source on GitHub 
    git clone https://github.com/64logic/micro-max-4.8-uci-core.git
cd micro-max-4.8-uci-core
make

    On FreeBSD, run gmake. On Windows, see the README.