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A minimal low-level HTTP client.

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Test Suite Package version

Do one thing, and do it well.

The HTTP Core package provides a minimal low-level HTTP client, which does one thing only. Sending HTTP requests.

It does not provide any high level model abstractions over the API, does not handle redirects, multipart uploads, building authentication headers, transparent HTTP caching, URL parsing, session cookie handling, content or charset decoding, handling JSON, environment based configuration defaults, or any of that Jazz.

Some things HTTP Core does do:

  • Sending HTTP requests.
  • Provides both sync and async interfaces.
  • Supports HTTP/1.1 and HTTP/2.
  • Async backend support for asyncio and trio.
  • Automatic connection pooling.
  • HTTP(S) proxy support.


Here's an example of making an HTTP GET request using httpcore...

async with httpcore.AsyncConnectionPool() as http:
    http_version, status_code, reason_phrase, headers, stream = await http.request(
        url=(b'https', b'', 443, b'/'),

        body = b''.join(chunk async for chunk in stream)
        await stream.close()

    print(status_code, body)


You probably don't want to be using HTTP Core directly. It might make sense if you're writing something like a proxy service in Python, and you just want something at the lowest possible level, but more typically you'll want to use a higher level client library, such as httpx.

The motivation for httpcore is:

  • To provide a reusable low-level client library, that other packages can then build on top of.
  • To provide a really clear interface split between the networking code and client logic, so that each is easier to understand and reason about in isolation.


All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog.

0.9.1 (May 27th, 2020)


  • Proper host resolution for sync case, including IPv6 support. (Pull #97)
  • Close outstanding connections when connection pool is closed. (Pull #98)

0.9.0 (May 21th, 2020)


  • URL port becomes an Optional[int] instead of int. (Pull #92)


  • Honor HTTP/2 max concurrent streams settings. (Pull #89, #90)
  • Remove incorrect debug log. (Pull #83)

0.8.4 (May 11th, 2020)


  • Logging via HTTPCORE_LOG_LEVEL and HTTPX_LOG_LEVEL environment variables and TRACE level logging. (Pull #79)


  • Reuse of connections on HTTP/2 in close concurrency situations. (Pull #81)

0.8.3 (May 6rd, 2020)


  • Include Host and Accept headers on proxy "CONNECT" requests.
  • De-duplicate any headers also contained in proxy_headers.
  • HTTP/2 flag not being passed down to proxy connections.

0.8.2 (May 3rd, 2020)


  • Fix connections using proxy forwarding requests not being added to the connection pool properly. (Pull #70)

0.8.1 (April 30th, 2020)


  • Allow inherintance of both httpcore.AsyncByteStream, httpcore.SyncByteStream without type conflicts.

0.8.0 (April 30th, 2020)


  • Fixed tunnel proxy support.

### Added

  • New TimeoutException base class.

0.7.0 (March 5th, 2020)

  • First integration with HTTPX.

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