This document contains important information about Nicotine+ design decisions and development procedures for maintainers, developers and code contributors alike.


Language and Toolkit


Nicotine+ is Python application, built on backend code from the PySoulSeek project started in 2001. We only allow Python code in the main client, as this makes it easy to distribute and run Nicotine+ on virtually any system. In turn, we are able to devote more time towards implementing bug fixes and additional functionality.

We aim to support the oldest minor Python 3 version still used by supported releases of distributions and operating systems. The minimum version Nicotine+ currently supports is 3.5.


Nicotine+ and its predecessors PySoulSeek and Nicotine were originally developed with GNU/Linux in mind, at a time when the official Soulseek client only supported Windows. The Nicotine project opted to use GTK as the GUI toolkit, as opposed to wxPython previously used by PySoulSeek. This decision was made due to various issues encountered in wxPython at the time, such as large memory overhead and long compile/build times.

We are content with GTK, and have no plans of switching to another toolkit.


Nicotine+ aims to be as portable as possible, providing access to the Soulseek network for people who cannot run the official Soulseek client. Nicotine+ runs on almost any architecture and system available, and has active users on a plethora of different systems. This also means that the introduction of an external software depencency can cause issues for both packagers and users.

Dependencies preinstalled on most systems, as well as modules included in the Python Standard Library, should be preferred whenever possible. Avoid introducing “convenient” and “new hotness” dependencies, if the standard library already includes the required functionality to some degree. If a new dependency is necessary, think about the following points:


Profiling code changes from time to time is important, to ensure that Nicotine+ performs well and uses few resources. Our goal is to develop a lightweight client than runs well on older hardware, as well as servers, which can be quite constrained.

Due to Python’s interpreted nature, addressing performance issues can be a challenge. There is no straightforward way of solving every performance issue, but these points generally help:

py-spy is an excellent tool for profiling Python applications in real time, and will save a lot of time in the long run.

Continuous Integration Testing

It is important that all patches pass unit testing. Unfortunately developers make all kinds of changes to their local development environment that can have unintended consequences. This means sometimes tests on the developer’s computer pass when they should not, and other times failing when they should not have.

To properly validate that things are working, continuous integration (CI) is required. This means compiling, performing local in-tree unit tests, installing through the system package manager, and finally testing the actually installed build artifacts to ensure they do what the user expects them to do.

The key thing to remember is that in order to do this properly, this all needs to be done within a realistic end user system that has not been unintentionally modified by a developer. This might mean a chroot container with the help of QEMU and KVM to verify that everything is working as expected. The hermetically sealed test environment validates that the developer’s expected steps for, as an example in the case of a library, compilation, linking, unit testing, and post installation testing are actually replicable.

There are different ways of performing CI on different distros. The most common one is via the international DEP-8 standard as used by hundreds of different operating systems.


On Debian based distributions, autopkgtest implements the DEP-8 standard. To create and use a build image environment for Ubuntu, follow these steps. First install the autopkgtest(1) tools:

sudo apt install autopkgtest

Next create the test image, substituting hirsute or amd64 for other releases or architectures:

autopkgtest-buildvm-ubuntu-cloud -r hirsute -a amd64

Test your changes on the host architecture in QEMU with KVM support and 8GB of RAM and four CPUs:

autopkgtest --shell-fail --apt-upgrade . -- \
      qemu --ram-size=8192 --cpus=4 --show-boot path_to_build_image.img \

Creating tests

Tests are defined in the test/ folder, and should be expanded to cover larger parts of the client when possible.


Nicotine+ tries to follow Semantic Versioning when possible. As cited in the specification:

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes,
MINOR version when you add functionality in a backwards compatible manner, and
PATCH version when you make backwards compatible bug fixes.

Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.

Release dates are not set in stone, as Nicotine+ development is done by volunteers in their spare time. However, keep the following points in mind:

Creating a new Nicotine+ release

The following is a step-by-step guide detailing what a Nicotine+ maintainer should do when releasing a new version of Nicotine+.

  1. Ensure that Nicotine+ works on at least these four systems: Windows, macOS, the oldest Ubuntu version we still support (18.04), as well as the newest Ubuntu release available.

  2. Ensure that the source distribution (sdist) includes all necessary files to run Nicotine+. A source distribution can be generated by running
    python3 sdist
  3. Add a new release note entry to Release notes should contain a user-readable list of noteworthy changes since the last release (not a list of commits), as well as a list of closed issues on GitHub.

  4. Increase the Nicotine+ version number / add new version entries in the master branch. Nicotine+ uses Semantic Versioning. The following files need to be modified:
    • data/org.nicotine_plus.Nicotine.metainfo.xml
    • debian/changelog
    • pynicotine/
  5. Ensure that the Windows and macOS packages generated by GitHub Actions still work. They can be found here.

  6. Create a new GitHub release.
    • Both the release tag and title should use the format “x.x.x”, e.g. 2.2.0.
    • Include the release notes from as the description.
    • Download the Windows and macOS packages previously generated by GitHub Actions to packaging/release/, and run
      python3 packaging/release/
    • Attach the resulting files to the new release.
  7. Generate a stable PPA release for Ubuntu / Debian. First, ensure that the repository mirror on Launchpad is up to date. Once it is, update the contents of the stable build recipe, replacing the previous commit hash with the one used for the release you tagged on GitHub. Then, generate stable builds by pressing Request build(s).

  8. Create a new release on PyPI by running
    python3 packaging/pypi/
  9. Create a new release on Flathub.