Contributing to JAX#

Everyone can contribute to JAX, and we value everyone’s contributions. There are several ways to contribute, including:

The JAX project follows Google’s Open Source Community Guidelines.

Ways to contribute#

We welcome pull requests, in particular for those issues marked with contributions welcome or good first issue.

For other proposals, we ask that you first open a GitHub Issue or Discussion to seek feedback on your planned contribution.

Contributing code using pull requests#

We do all of our development using git, so basic knowledge is assumed.

Follow these steps to contribute code:

  1. Sign the Google Contributor License Agreement (CLA). For more information, see the Pull Request Checklist below.

  2. Fork the JAX repository by clicking the Fork button on the repository page. This creates a copy of the JAX repository in your own account.

  3. Install Python >= 3.9 locally in order to run tests.

  4. pip installing your fork from source. This allows you to modify the code and immediately test it out:

    git clone
    cd jax
    pip install -r build/test-requirements.txt  # Installs all testing requirements.
    pip install -e ".[cpu]"  # Installs JAX from the current directory in editable mode.
  5. Add the JAX repo as an upstream remote, so you can use it to sync your changes.

    git remote add upstream
  6. Create a branch where you will develop from:

    git checkout -b name-of-change

    And implement your changes using your favorite editor (we recommend Visual Studio Code).

  7. Make sure your code passes JAX’s lint and type checks, by running the following from the top of the repository:

    pip install pre-commit
    pre-commit run --all

    See Linting and Type-checking for more details.

  8. Make sure the tests pass by running the following command from the top of the repository:

    pytest -n auto tests/

    JAX’s test suite is quite large, so if you know the specific test file that covers your changes, you can limit the tests to that; for example:

    pytest -n auto tests/

    You can narrow the tests further by using the pytest -k flag to match particular test names:

    pytest -n auto tests/ -k testLogSumExp

    JAX also offers more fine-grained control over which particular tests are run; see Running the tests for more information.

  9. Once you are satisfied with your change, create a commit as follows ( how to write a commit message):

    git add ...
    git commit -m "Your commit message"

    Then sync your code with the main repo:

    git fetch upstream
    git rebase upstream/main

    Finally, push your commit on your development branch and create a remote branch in your fork that you can use to create a pull request from:

    git push --set-upstream origin name-of-change

    Please ensure your contribution is a single commit (see Single-change commits and pull requests)

  10. Create a pull request from the JAX repository and send it for review. Check the JAX pull request checklist for considerations when preparing your PR, and consult GitHub Help if you need more information on using pull requests.

JAX pull request checklist#

As you prepare a JAX pull request, here are a few things to keep in mind:

Google contributor license agreement#

Contributions to this project must be accompanied by a Google Contributor License Agreement (CLA). You (or your employer) retain the copyright to your contribution; this simply gives us permission to use and redistribute your contributions as part of the project. Head over to to see your current agreements on file or to sign a new one.

You generally only need to submit a CLA once, so if you’ve already submitted one (even if it was for a different project), you probably don’t need to do it again. If you’re not certain whether you’ve signed a CLA, you can open your PR and our friendly CI bot will check for you.

Single-change commits and pull requests#

A git commit ought to be a self-contained, single change with a descriptive message. This helps with review and with identifying or reverting changes if issues are uncovered later on.

Pull requests typically comprise a single git commit. (In some cases, for instance for large refactors or internal rewrites, they may contain several.) In preparing a pull request for review, you may need to squash together multiple commits. We ask that you do this prior to sending the PR for review if possible. The git rebase -i command might be useful to this end.

Linting and Type-checking#

JAX uses mypy and ruff to statically test code quality; the easiest way to run these checks locally is via the pre-commit framework:

pip install pre-commit
pre-commit run --all

If your pull request touches documentation notebooks, this will also run some checks on those (See Update notebooks for more details).

Full GitHub test suite#

Your PR will automatically be run through a full test suite on GitHub CI, which covers a range of Python versions, dependency versions, and configuration options. It’s normal for these tests to turn up failures that you didn’t catch locally; to fix the issues you can push new commits to your branch.

Restricted test suite#

Once your PR has been reviewed, a JAX maintainer will mark it as Pull Ready. This will trigger a larger set of tests, including tests on GPU and TPU backends that are not available via standard GitHub CI. Detailed results of these tests are not publicly viewable, but the JAX maintainer assigned to your PR will communicate with you regarding any failures these might uncover; it’s not uncommon, for example, that numerical tests need different tolerances on TPU than on CPU.