Developers - official-stockfish/Stockfish GitHub Wiki

Stockfish's improvement over the last decade has been a great community effort.
Nowadays most development talk takes place on Discord.

There are many ways to contribute to Stockfish:

• Stockfish (C++)
• nnue-pytorch (C++ and Python)
• Donating hardware

If you want to contribute to Stockfish directly, you can do so in a couple of ways.
Follow the steps described in our Fishtest wiki to create your first test.
It is advised to first follow the development setup steps for your platform.

New commits to stockfish can mostly be categorised in 2 categories:

• Non functional changes: These are changes that don't change the search behaviour and can be directly submitted as pull requests.
• Functional changes: These change the search behaviour and lead to a different search tree. Every functional patch has to be verified by Fishtest, our testing framework.

NNUE Pytorch is the trainer for Stockfish's neural network.
Usually changes here are tested by training a new network and testing it against the current network via Fishtest.

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

This section provides instructions for setting up your environment to develop and compile Stockfish on different operating systems.

sudo apt install build-essential git

sudo apt install clang-format-20

sudo xcode-select --install

brew install clang-format@20

#!/bin/bash

if ! which clang-format-18 >/dev/null; then
    CLANG_FORMAT=clang-format
else
    CLANG_FORMAT=clang-format-18
fi

# Extracted from the Makefile
SRCS=$(awk '/^SRCS = /{flag=1; sub(/^SRCS = /,""); print} /^$/{flag=0} flag && !/^SRCS = /{print}' ./src/Makefile | tr -d '\\' | xargs echo | tr ' ' '\n' | sed 's|^|./src/|')
HEADERS=$(awk '/^HEADERS = /{flag=1; sub(/^HEADERS = /,""); print} /^$/{flag=0} flag && !/^HEADERS = /{print}' ./src/Makefile | tr -d '\\' | xargs echo | tr ' ' '\n' | sed 's|^|./src/|')

while read local_ref local_sha remote_ref remote_sha; do
    if [[ "$remote_ref" == "refs/heads/master" ]]; then
        # Check open diffs
        if [[ -n $(git status --porcelain) ]]; then
            echo "Please commit or stash your changes before pushing."
            exit 1
        fi

        # Check formatting
        if ! $CLANG_FORMAT --dry-run -Werror -style=file $SRCS $HEADERS; then
            echo "Please run 'make format' to fix formatting issues and rebase the last commit."
            exit 1
        fi

        # Iterate through commits
        for commit in $(git rev-list --no-merges $remote_sha..$local_sha); do
            commit_msg=$(git log --format=%B -n 1 $commit)

            # bench regex as defined in ci
            # check for the existence of a bench in the commit message
            bench_regex='\b[Bb]ench[ :]+[1-9][0-9]{5,7}\b'
            if echo "$commit_msg" | grep -m 1 -o -x -E "$bench_regex" >/dev/null; then
                continue
            fi

            # check for the existence of "No functional change" in the commit message
            no_functional_change_regex='\b[Nn]o[[:space:]][Ff]unctional[[:space:]][Cc]hange\b'
            if echo "$commit_msg" | grep -o -x -E "$no_functional_change_regex" >/dev/null; then
                continue
            fi

            echo "Commit $commit does not contain a Bench or 'No functional change'."
            exit 1
        done
    fi
done

exit 0

1. Review the Terms of Use: First and foremost, you should read our Terms of Use and adhere to them carefully.
2. Understand the UCI Protocol: Stockfish is a UCI chess engine, meaning it communicates via the Universal Chess Interface (UCI) protocol. You can find a detailed explanation of this protocol here. Basic demonstrations of the available commands are available in UCI & Commands.
3. Implement Process Communication: Your application will need to interact with the Stockfish executable. This typically involves:
   • Opening the Stockfish executable.
   • Writing commands to its stdin.
   • Listening for Stockfish's output, which will appear on its stdout.

• NodeJS: You can follow this guide on how to communicate with a program.
  • Basic example of using Stockfish on the web: https://github.com/Disservin/html-js-stockfish
• Python: Use python-chess (pip install chess): https://python-chess.readthedocs.io/en/latest/engine.html
• C++: Boost.Process can be used for easy process communication.
• Rust: Examine the documentation on how to spawn a Command.

I want Stockfish to comment on the move it made, what do I need to do?

That is not possible. You will have to write your own logic to create such a feature.

I want to get an evaluation of the current position.

In order to get an accurate evaluation of the current position, you need to use the UCI go command with a specified limit (e.g., time, depth, nodes).
An eval command is available, but it only provides a static and very rough evaluation of the position without any search involved and is not recommended for most use cases.

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. This also means that you can distribute Stockfish alongside your proprietary system, but to do this validly, you must make sure that Stockfish and your program communicate at arm's length, that they are not combined in a way that would make them effectively a single program.

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.