With the release of psutil 7.1.2, wheels for free-threaded Python are now available. This milestone was achieved largely through a community effort, as several internal refactorings to the C code were required to make it possible (see issue #2565). Many of these changes were contributed by Lysandros Nikolaou. Thanks to him for the effort and for bearing with me in code reviews! ;-)

What is free-threaded Python?

Free-threaded Python (available since Python 3.13) refers to Python builds that are compiled with the GIL (Global Interpreter Lock) disabled, allowing true parallel execution of Python bytecodes across multiple threads. This is particularly beneficial for CPU-bound applications, as it enables better utilization of multi-core processors.

The state of free-threaded wheels

According to Hugo van Kemenade's free-threaded wheels tracker, the adoption of free-threaded wheels among the top 360 most-downloaded PyPI packages with C extensions is still limited. Only 128 out of these 360 packages provide wheels compiled for free-threaded Python, meaning they can run on Python builds with the GIL disabled. This shows that, while progress has been made, most popular packages with C extensions still do not offer ready-made wheels for free-threaded Python.

What it means for users

When a library author provides a wheel, users can install a pre-compiled binary package without having to build it from source. This is especially important for packages with C extensions, like psutil, which is largely written in C. Such packages often have complex build requirements and require installing a C compiler. On Windows, that means installing Visual Studio or the Build Tools, which can take several gigabytes and a significant setup effort. Providing wheels spare users from this hassle, makes installation far simpler, and is effectively essential for the users of that package. You basically pip install psutil and you're done.

What it means for library authors

Currently, universal wheels for free-threaded Python do not exist. Each wheel must be built specifically for a Python version. Right now authors must create separate wheels for Python 3.13 and 3.14. Which means distributing a lot of files already:

psutil-7.1.2-cp313-cp313t-macosx_10_13_x86_64.whl
psutil-7.1.2-cp313-cp313t-macosx_11_0_arm64.whl
psutil-7.1.2-cp313-cp313t-manylinux2010_x86_64.manylinux_2_12_x86_64.manylinux_2_28_x86_64.whl
psutil-7.1.2-cp313-cp313t-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl
psutil-7.1.2-cp313-cp313t-win_amd64.whl
psutil-7.1.2-cp313-cp313t-win_arm64.whl
psutil-7.1.2-cp314-cp314t-macosx_10_15_x86_64.whl
psutil-7.1.2-cp314-cp314t-macosx_11_0_arm64.whl
psutil-7.1.2-cp314-cp314t-manylinux2010_x86_64.manylinux_2_12_x86_64.manylinux_2_28_x86_64.whl
psutil-7.1.2-cp314-cp314t-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl
psutil-7.1.2-cp314-cp314t-win_amd64.whl
psutil-7.1.2-cp314-cp314t-win_arm64.whl

This also multiplies CI jobs and slows down the test matrix (see build.yml). A true universal wheel would greatly reduce this overhead, allowing a single wheel to support multiple Python versions and platforms. Hopefully, Python 3.15 will simplify this process. Two competing proposals, PEP 803 and PEP 809, aim to standardize wheel naming and metadata to allow producing a single wheel that covers multiple Python versions. That would drastically reduce distribution complexity for library authors, and it's fair to say it's essential for free-threaded CPython to truly succeed.

How to install free-threaded psutil

You can now install psutil for free-threaded Python directly via pip:

pip install psutil --only-binary=:all:

This ensures you get the pre-compiled wheels without triggering a source build.