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WASIX / LANGUAGE GUIDE

Install Python packages for WASIX

Use familiar Python packages in WebAssembly. The WASIX Python registry  provides prebuilt wheels, including native extensions compiled for wasix_wasm32.

The registry lists 434 packages, checked on September 12, 2026. Browse the complete package index  for available packages and versions, including FastAPI, NumPy, pandas, Pydantic, and cryptography.

Install packages with pip

Run this command on your development machine or in your build environment:

pip install fastapi \
  --index-url https://python-registry.wasmer.app/all/simple/ \
  --platform wasix_wasm32 \
  --python-version 3.13 \
  --only-binary=:all: \
  --target ./wasix-packages

Replace fastapi with another package from the registry, or provide several package names. Packages are installed into ./wasix-packages in your current host directory.

OptionPurpose
--index-urlUse the complete WASIX package index, including dependencies.
--platform wasix_wasm32Select wheels for WASIX instead of your host operating system.
--python-version 3.13Select wheels compatible with the target Python interpreter. Change this to match your WASIX Python version, such as 3.14.
--only-binary=:all:Install prebuilt wheels without attempting source builds on the host.
--target ./wasix-packagesPut packages and dependencies in a directory to bundle with your application.

The registry’s /all/simple/ index includes every published package and its packaged dependencies. Its /simple/ index is a smaller selection of WASIX-specific packages intended for use alongside PyPI. Use /all/simple/ for the self-contained installation command above.

Install from a requirements file

Use the same options with your project’s requirements.txt:

pip install -r requirements.txt \
  --index-url https://python-registry.wasmer.app/all/simple/ \
  --platform wasix_wasm32 \
  --python-version 3.13 \
  --only-binary=:all: \
  --target ./wasix-packages

The registry publishes versions with a +wasix.N suffix identifying the WASIX build. Check the package’s index page when pinning versions.

Run it with Wasmer

After installing the packages, install Wasmer 7 or newer  and run the Python package  from the same host directory where you ran pip:

wasmer run python/python@=3.13.19 \
  --volume ./wasix-packages:/packages \
  --env PYTHONPATH=/packages \
  -- -c "import fastapi; print('FastAPI', fastapi.__version__)"

The command imports FastAPI inside WASIX Python and prints FastAPI followed by the installed version. A successful import verifies that Python can load the package and the dependencies it imports, including native extensions.

  • --volume maps the host directory from the pip install step to /packages inside the sandbox. If you changed the installation directory, update the host path before the colon too.
  • --env PYTHONPATH=/packages adds that guest directory to Python’s import path.
  • -- separates Wasmer options from Python’s -c argument.
  • python/python@=3.13.19 pins the registry package containing CPython 3.13, matching the install command’s --python-version 3.13.

To run your own script, mount its directory too and pass its guest path instead of -c. For example, with app.py in the current directory:

wasmer run python/python@=3.13.19 \
  --volume ./wasix-packages:/packages \
  --volume .:/app \
  --env PYTHONPATH=/packages \
  -- /app/app.py

WASIX native extensions are intended for the WASIX interpreter; importing them with your host’s macOS or Linux Python will not work. See the Wasmer CLI reference  for more runtime options.

If pip cannot find a matching distribution, check the package’s published Python versions and platform tags, and make sure your requirements can be resolved from the registry. Package availability and supported Python versions vary by release.

Next steps

ExamplesAPI Reference