Package compatibility tracker:
Python 3.13 free-threading and subinterpreters

The following table summarises very basic compatibility of the 500 most downloaded Python packages with Python 3.13's free-threading build and subinterpreters in the standard build. It was generated with a script that runs two tests for each package:

• Install the package in a fresh Docker container with the free-threading Python build. Import the package and check that the GIL remains disabled (i.e. the package doesn't declare that it requires the GIL).
• Install the package in a fresh Docker container with the standard Python build. Start a subinterpreter and check that the package can be imported there (i.e. the package doesn't forbid importing outside of the main interpreter).

Do note that these are simple tests that do not exercise most of the package code, and so cannot truly guarantee compatibility. In particular, since we are dealing with thread safety, many issues are likely to be found only by complex, multi-threaded tests. See py-free-threading.github.io for a shorter list of packages that have been tested more thoroughly.

It is also important to realise that the free-threading build is very new and experimental (see the docs), and that subinterpreters are not even officially supported yet (watch PEP 734 for updates). None of the package maintainers are obliged to support these experimental features. In some cases this may require substantial changes to the package, or even to major upstream dependencies such as Cython or PyO3. Please be patient and understanding – maintaining packages and adapting to major changes in Python is a lot of work.

This tracker page is open source. If you found an error in this table (such as a false positive or false negative), would like to add a package, or have any other feedback, please open an issue on Github.