Skip to main content

A minimal low-level HTTP client.

Project description


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, trio and curio.
  • Automatic connection pooling.
  • HTTP(S) proxy support.


For HTTP/1.1 only support, install with...

$ pip install httpcore

For HTTP/1.1 and HTTP/2 support, install with...

$ pip install httpcore[http2]


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

with httpcore.SyncConnectionPool() as http:
    status_code, headers, stream, extensions = http.handle_request(
        url=(b'https', b'', 443, b'/'),
        headers=[(b'host', b''), (b'user-agent', b'httpcore')],
    body =
    print(status_code, body)

Or, using async...

async with httpcore.AsyncConnectionPool() as http:
    status_code, headers, stream, extensions = await http.handle_async_request(
        url=(b'https', b'', 443, b'/'),
        headers=[(b'host', b''), (b'user-agent', b'httpcore')],
    body = await stream.aread()
    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.

0.13.6 (June 15th, 2021)


  • Close sockets when read or write timeouts occur. (Pull #365)

0.13.5 (June 14th, 2021)


  • Resolved niggles with AnyIO EOF behaviours. (Pull #358, #362)

0.13.4 (June 9th, 2021)


  • Improved error messaging when URL scheme is missing, or a non HTTP(S) scheme is used. (Pull #354)


  • Switched to anyio as the default backend implementation when running with asyncio. Resolves some awkward TLS timeout issues.

0.13.3 (May 6th, 2021)


  • Support HTTP/2 prior knowledge, using httpcore.SyncConnectionPool(http1=False). (Pull #333)


  • Handle cases where environment does not provide select.poll support. (Pull #331)

0.13.2 (April 29th, 2021)


  • Improve error message for specific case of RemoteProtocolError where server disconnects without sending a response. (Pull #313)

0.13.1 (April 28th, 2021)


  • More resiliant testing for closed connections. (Pull #311)
  • Don't raise exceptions on ungraceful connection closes. (Pull #310)

0.13.0 (April 21st, 2021)

The 0.13 release updates the core API in order to match the HTTPX Transport API, introduced in HTTPX 0.18 onwards.

An example of making requests with the new interface is:

with httpcore.SyncConnectionPool() as http:
    status_code, headers, stream, extensions = http.handle_request(
        url=(b'https', b'', 443, b'/'),
        headers=[(b'host', b''), (b'user-agent', b'httpcore')]
    body =
    print(status_code, body)


  • The .request() method is now handle_request(). (Pull #296)
  • The .arequest() method is now .handle_async_request(). (Pull #296)
  • The headers argument is no longer optional. (Pull #296)
  • The stream argument is no longer optional. (Pull #296)
  • The ext argument is now named extensions, and is no longer optional. (Pull #296)
  • The "reason" extension keyword is now named "reason_phrase". (Pull #296)
  • The "reason_phrase" and "http_version" extensions now use byte strings for their values. (Pull #296)
  • The httpcore.PlainByteStream() class becomes httpcore.ByteStream(). (Pull #296)


  • Streams now support a .read() interface. (Pull #296)


  • Task cancelation no longer leaks connections from the connection pool. (Pull #305)

0.12.3 (December 7th, 2020)


  • Abort SSL connections on close rather than waiting for remote EOF when using asyncio. (Pull #167)
  • Fix exception raised in case of connect timeouts when using the anyio backend. (Pull #236)
  • Fix Host header precedence for :authority in HTTP/2. (Pull #241, #243)
  • Handle extra edge case when detecting for socket readability when using asyncio. (Pull #242, #244)
  • Fix asyncio SSL warning when using proxy tunneling. (Pull #249)

0.12.2 (November 20th, 2020)


  • Properly wrap connect errors on the asyncio backend. (Pull #235)
  • Fix ImportError occurring on Python 3.9 when using the HTTP/1.1 sync client in a multithreaded context. (Pull #237)

0.12.1 (November 7th, 2020)


  • Add connect retries. (Pull #221)


  • Tweak detection of dropped connections, resolving an issue with open files limits on Linux. (Pull #185)
  • Avoid leaking connections when establishing an HTTP tunnel to a proxy has failed. (Pull #223)
  • Properly wrap OS errors when using trio. (Pull #225)

0.12.0 (October 6th, 2020)


  • HTTP header casing is now preserved, rather than always sent in lowercase. (#216 and python-hyper/h11#104)


  • Add Python 3.9 to officially supported versions.


  • Gracefully handle a stdlib asyncio bug when a connection is closed while it is in a paused-for-reading state. (#201)

0.11.1 (September 28nd, 2020)


  • Add await to async semaphore release() coroutine (#197)
  • Drop incorrect curio classifier (#192)

0.11.0 (September 22nd, 2020)

The Transport API with 0.11.0 has a couple of significant changes.

Firstly we've moved changed the request interface in order to allow extensions, which will later enable us to support features such as trailing headers, HTTP/2 server push, and CONNECT/Upgrade connections.

The interface changes from:

def request(method, url, headers, stream, timeout):
    return (http_version, status_code, reason, headers, stream)

To instead including an optional dictionary of extensions on the request and response:

def request(method, url, headers, stream, ext):
    return (status_code, headers, stream, ext)

Having an open-ended extensions point will allow us to add later support for various optional features, that wouldn't otherwise be supported without these API changes.

In particular:

  • Trailing headers support.
  • HTTP/2 Server Push
  • sendfile.
  • Exposing raw connection on CONNECT, Upgrade, HTTP/2 bi-di streaming.
  • Exposing debug information out of the API, including template name, template context.

Currently extensions are limited to:

  • request: timeout - Optional. Timeout dictionary.
  • response: http_version - Optional. Include the HTTP version used on the response.
  • response: reason - Optional. Include the reason phrase used on the response. Only valid with HTTP/1.*.

See for the history behind this.

Secondly, the async version of request is now namespaced as arequest.

This allows concrete transports to support both sync and async implementations on the same class.


  • Add curio support. (Pull #168)
  • Add anyio support, with backend="anyio". (Pull #169)


  • Update the Transport API to use 'ext' for optional extensions. (Pull #190)
  • Update the Transport API to use .request and .arequest so implementations can support both sync and async. (Pull #189)

0.10.2 (August 20th, 2020)


  • Added Unix Domain Socket support. (Pull #139)


  • Always include the port on proxy CONNECT requests. (Pull #154)
  • Fix max_keepalive_connections configuration. (Pull #153)
  • Fixes behaviour in HTTP/1.1 where server disconnects can be used to signal the end of the response body. (Pull #164)

0.10.1 (August 7th, 2020)

  • Include max_keepalive_connections on AsyncHTTPProxy/SyncHTTPProxy classes.

0.10.0 (August 7th, 2020)

The most notable change in the 0.10.0 release is that HTTP/2 support is now fully optional.

Use either pip install httpcore for HTTP/1.1 support only, or pip install httpcore[http2] for HTTP/1.1 and HTTP/2 support.


  • HTTP/2 support becomes optional. (Pull #121, #130)
  • Add local_address=... support. (Pull #100, #134)
  • Add PlainByteStream, IteratorByteStream, AsyncIteratorByteStream. The AsyncByteSteam and SyncByteStream classes are now pure interface classes. (#133)
  • Add LocalProtocolError, RemoteProtocolError exceptions. (Pull #129)
  • Add UnsupportedProtocol exception. (Pull #128)
  • Add .get_connection_info() method. (Pull #102, #137)
  • Add better TRACE logs. (Pull #101)


  • max_keepalive is deprecated in favour of max_keepalive_connections. (Pull #140)


  • Improve handling of server disconnects. (Pull #112)

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.

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for httpcore, version 0.13.6
Filename, size File type Python version Upload date Hashes
Filename, size httpcore-0.13.6-py3-none-any.whl (58.8 kB) File type Wheel Python version py3 Upload date Hashes View
Filename, size httpcore-0.13.6.tar.gz (45.3 kB) File type Source Python version None Upload date Hashes View

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring DigiCert DigiCert EV certificate Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page