urllib3 is a community-maintained project and we happily accept contributions.

If you wish to add a new feature or fix a bug:

  1. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug. There is a Contributor Friendly tag for issues that should be ideal for people who are not very familiar with the codebase yet.
  2. Fork the urllib3 repository on Github to start making your changes.
  3. Write a test which shows that the bug was fixed or that the feature works as expected.
  4. Format your changes with black using command $ nox -s blacken and lint your changes using command nox -s lint.
  5. Send a pull request and bug the maintainer until it gets merged and published. :) Make sure to add yourself to CONTRIBUTORS.txt.

Setting up your development environment

In order to setup the development environment all that you need is nox installed in your machine:

$ pip install --user --upgrade nox

Running the tests

We use some external dependencies, multiple interpreters and code coverage analysis while running test suite. Our handles much of this for you:

$ nox --sessions test-2.7 test-3.7
[ Nox will create virtualenv, install the specified dependencies, and run the commands in order.]
nox > Running session test-2.7
nox > Session test-2.7 was successful.
nox > Running session test-3.7
nox > Session test-3.7 was successful.

There is also a nox command for running all of our tests and multiple python versions.

$ nox –sessions test

Note that code coverage less than 100% is regarded as a failing run. Some platform-specific tests are skipped unless run in that platform. To make sure the code works in all of urllib3’s supported platforms, you can run our tox suite:

$ nox --sessions test
[ Nox will create virtualenv, install the specified dependencies, and run the commands in order.]
nox > Session test-2.7 was successful.
nox > Session test-3.4 was successful.
nox > Session test-3.5 was successful.
nox > Session test-3.6 was successful.
nox > Session test-3.7 was successful.
nox > Session test-3.8 was successful.
nox > Session test-pypy was successful.

Our test suite runs continuously on Travis CI with every pull request.


A release candidate can be created by any contributor by creating a branch named release-x.x where x.x is the version of the proposed release.

  • Update CHANGES.rst and urllib3/ with the proper version number and commit the changes to release-x.x.
  • Open a pull request to merge the release-x.x branch into the master branch.
  • Integration tests are run against the release candidate on Travis. From here on all the steps below will be handled by a maintainer so unless you receive review comments you are done here.
  • Once the pull request is squash merged into master the merging maintainer will tag the merge commit with the version number:
    • git tag -a 1.24.1 [commit sha]
    • git push origin master --tags
  • After the commit is tagged Travis will build the tagged commit and upload the sdist and wheel to PyPI and create a draft release on GitHub for the tag. The merging maintainer will ensure that the PyPI sdist and wheel are properly uploaded.
  • The merging maintainer will mark the draft release on GitHub as an approved release.


Tidelift Professional support for urllib3 is available as part of the Tidelift Subscription. Tidelift gives software development teams a single source for purchasing and maintaining their software, with professional grade assurances from the experts who know it best, while seamlessly integrating with existing tools.

Please consider sponsoring urllib3 development, especially if your company benefits from this library.

Your contribution will go towards adding new features to urllib3 and making sure all functionality continues to meet our high quality standards.

We also welcome sponsorship in the form of time. We greatly appreciate companies who encourage employees to contribute on an ongoing basis during their work hours. Please let us know and we’ll be glad to add you to our sponsors list!

A grant for contiguous full-time development has the biggest impact for progress. Periods of 3 to 10 days allow a contributor to tackle substantial complex issues which are otherwise left to linger until somebody can’t afford to not fix them.

Contact @theacodes or @shazow to arrange a grant for a core contributor.

Huge thanks to all the companies and individuals who financially contributed to the development of urllib3. Please send a PR if you’ve donated and would like to be listed.