A free and strong UCI chess engine
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Simplify sudden death time optimization
Passed Sudden Death STC:
https://tests.stockfishchess.org/tests/view/68455fe5375c2b77d9855351
LLR: 2.91 (-2.94,2.94) <-1.75,0.25>
Total: 49248 W: 13008 L: 12798 D: 23442
Ptnml(0-2): 309, 5491, 12821, 5687, 316

Passed Sudden Death LTC:
https://tests.stockfishchess.org/tests/view/6845a392375c2b77d98553cf
LLR: 3.01 (-2.94,2.94) <-1.75,0.25>
Total: 551070 W: 141699 L: 142031 D: 267340
Ptnml(0-2): 1923, 60608, 150916, 60054, 2034

Passed Standard STC:
https://tests.stockfishchess.org/tests/view/683c5ebb6ec7634154f9d989
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 142624 W: 36808 L: 36709 D: 69107
Ptnml(0-2): 302, 15448, 39745, 15483, 334

Passed Standard LTC:
https://tests.stockfishchess.org/tests/view/683f1a4f6ec7634154f9dc5a
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 146922 W: 37381 L: 37296 D: 72245
Ptnml(0-2): 69, 13552, 46117, 13671, 52

closes https://github.com/official-stockfish/Stockfish/pull/6132

Bench: 2249459
2025-07-02 18:41:46 +02:00
.github Disable linux gcc riscv64 (#6145) 2025-06-29 12:33:20 +02:00
scripts ci: add tests and artifacts for windows-11-arm 2025-05-21 07:29:57 +02:00
src Simplify sudden death time optimization 2025-07-02 18:41:46 +02:00
tests Enforce minimum compiler versions 2025-06-02 21:09:19 +02:00
.clang-format Update clang-format to v20 2025-05-23 08:54:06 +02:00
.git-blame-ignore-revs Add .git-blame-ignore-revs 2024-01-07 13:38:55 +01:00
.gitignore Port instrumented testing to python 2024-09-17 20:24:17 +02:00
AUTHORS Adjust futility pruning thresholds using history 2025-05-25 21:24:09 +02:00
CITATION.cff Add CITATION.cff file 2023-03-05 16:16:16 +01:00
CONTRIBUTING.md Fix clang-format version in CONTRIBUTING.md 2025-06-02 21:38:53 +02:00
Copying.txt Update links in license 2023-10-08 07:38:13 +02:00
README.md Add Leela Data Attribution 2024-12-08 19:56:01 +01:00
Top CPU Contributors.txt Update CPU contributors 2025-03-29 11:52:50 +01:00

Stockfish

Stockfish

A free and strong UCI chess engine.
Explore Stockfish docs »

Report bug · Open a discussion · Discord · Blog

Build License
Release Commits
Website Fishtest Discord

Overview

Stockfish is a free and strong UCI chess engine derived from Glaurung 2.1 that analyzes chess positions and computes the optimal moves.

Stockfish does not include a graphical user interface (GUI) that is required to display a chessboard and to make it easy to input moves. These GUIs are developed independently from Stockfish and are available online. Read the documentation for your GUI of choice for information about how to use Stockfish with it.

See also the Stockfish documentation for further usage help.

Files

This distribution of Stockfish consists of the following files:

  • README.md, the file you are currently reading.

  • Copying.txt, a text file containing the GNU General Public License version 3.

  • AUTHORS, a text file with the list of authors for the project.

  • src, a subdirectory containing the full source code, including a Makefile that can be used to compile Stockfish on Unix-like systems.

  • a file with the .nnue extension, storing the neural network for the NNUE evaluation. Binary distributions will have this file embedded.

Contributing

See Contributing Guide.

Donating hardware

Improving Stockfish requires a massive amount of testing. You can donate your hardware resources by installing the Fishtest Worker and viewing the current tests on Fishtest.

Improving the code

In the chessprogramming wiki, many techniques used in Stockfish are explained with a lot of background information. The section on Stockfish describes many features and techniques used by Stockfish. However, it is generic rather than focused on Stockfish's precise implementation.

The engine testing is done on Fishtest. If you want to help improve Stockfish, please read this guideline first, where the basics of Stockfish development are explained.

Discussions about Stockfish take place these days mainly in the Stockfish Discord server. This is also the best place to ask questions about the codebase and how to improve it.

Compiling Stockfish

Stockfish has support for 32 or 64-bit CPUs, certain hardware instructions, big-endian machines such as Power PC, and other platforms.

On Unix-like systems, it should be easy to compile Stockfish directly from the source code with the included Makefile in the folder src. In general, it is recommended to run make help to see a list of make targets with corresponding descriptions. An example suitable for most Intel and AMD chips:

cd src
make -j profile-build

Detailed compilation instructions for all platforms can be found in our documentation. Our wiki also has information about the UCI commands supported by Stockfish.

Terms of use

Stockfish is free and distributed under the GNU General Public License version 3 (GPL v3). Essentially, this means you are free to do almost exactly what you want with the program, including distributing it among your friends, making it available for download from your website, selling it (either by itself or as part of some bigger software package), or using it as the starting point for a software project of your own.

The only real limitation is that whenever you distribute Stockfish in some way, you MUST always include the license and the full source code (or a pointer to where the source code can be found) to generate the exact binary you are distributing. If you make any changes to the source code, these changes must also be made available under GPL v3.

Acknowledgements

Stockfish uses neural networks trained on data provided by the Leela Chess Zero project, which is made available under the Open Database License (ODbL).