Python HTTP library with thread-safe connection pooling, file post support, sanity friendly, and more.
Python Other
Latest commit 36d778f Jul 26, 2016 @sigmavirus24 sigmavirus24 committed on GitHub Merge pull request #932 from scop/spelling
Spelling fixes




  • Re-use the same socket connection for multiple requests (HTTPConnectionPool and HTTPSConnectionPool) (with optional client-side certificate verification).
  • File posting (encode_multipart_formdata).
  • Built-in redirection and retries (optional).
  • Supports gzip and deflate decoding.
  • Proxy over HTTP or SOCKS.
  • Thread-safe and sanity-safe.
  • Works with AppEngine, gevent, and eventlib.
  • Tested on Python 2.6+, Python 3.3+, and PyPy, with 100% unit test coverage.
  • Small and easy to understand codebase perfect for extending and building upon. For a more comprehensive solution, have a look at Requests which is also powered by urllib3.

You might already be using urllib3!

urllib3 powers many great Python libraries, including pip and requests.

What's wrong with urllib and urllib2?

There are two critical features missing from the Python standard library: Connection re-using/pooling and file posting. It's not terribly hard to implement these yourself, but it's much easier to use a module that already did the work for you.

The Python standard libraries urllib and urllib2 have little to do with each other. They were designed to be independent and standalone, each solving a different scope of problems, and urllib3 follows in a similar vein.

Why do I want to reuse connections?

Performance. When you normally do a urllib call, a separate socket connection is created with each request. By reusing existing sockets (supported since HTTP 1.1), the requests will take up less resources on the server's end, and also provide a faster response time at the client's end. With some simple benchmarks (see test/ ), downloading 15 URLs from is about twice as fast when using HTTPConnectionPool (which uses 1 connection) than using plain urllib (which uses 15 connections).

This library is perfect for:

  • Talking to an API
  • Crawling a website
  • Any situation where being able to post files, handle redirection, and retrying is useful. It's relatively lightweight, so it can be used for anything!


Go to for more nice syntax-highlighted examples.

But, long story short:

import urllib3

http = urllib3.PoolManager()

r = http.request('GET', '')

print r.status,

The PoolManager will take care of reusing connections for you whenever you request the same host. For more fine-grained control of your connection pools, you should look at ConnectionPool.

Run the tests

We use some external dependencies, multiple interpreters and code coverage analysis while running test suite. Our Makefile handles much of this for you as long as you're running it inside of a virtualenv:

$ make test
[... magically installs dependencies and runs tests on your virtualenv]
Ran 182 tests in 1.633s


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:

$ make test-all
[... tox creates a virtualenv for every platform and runs tests inside of each]
py26: commands succeeded
py27: commands succeeded
py32: commands succeeded
py33: commands succeeded
py34: commands succeeded

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


Thank you for giving back to urllib3. Please meet our jolly team of code-sherpas:



Getting Started

  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. Send a pull request and bug the maintainer until it gets merged and published. :) Make sure to add yourself to CONTRIBUTORS.txt.


If your company benefits from this library, please consider sponsoring its development.