---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLMOPT_PIPELINING
Section: 3
Source: libcurl
See-also:
  - CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE (3)
  - CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE (3)
  - CURLMOPT_MAXCONNECTS (3)
  - CURLMOPT_MAX_HOST_CONNECTIONS (3)
  - CURLMOPT_MAX_PIPELINE_LENGTH (3)
  - CURLMOPT_PIPELINING_SITE_BL (3)
Protocol:
  - HTTP
Added-in: 7.16.0
---

# NAME

CURLMOPT_PIPELINING - enable HTTP multiplexing

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PIPELINING, long bitmask);
~~~

# DESCRIPTION

Pass in the correct value in the **bitmask** parameter to instruct libcurl to
enable multiplexing for this multi handle.

With multiplexing enabled, libcurl attempts to do multiple transfers over the
same connection when doing parallel transfers to the same hosts.

## CURLPIPE_NOTHING (0)

Make no attempts at multiplexing.

## CURLPIPE_HTTP1 (1)

This bit is deprecated and has no effect since version 7.62.0.

## CURLPIPE_MULTIPLEX (2)

If this bit is set, libcurl tries to multiplex the new transfer over an
existing connection if possible. This requires HTTP/2 or HTTP/3.

# DEFAULT

**CURLPIPE_MULTIPLEX**

# %PROTOCOLS%

# EXAMPLE

~~~c
int main(void)
{
  CURLM *m = curl_multi_init();
  /* try HTTP/2 multiplexing */
  curl_multi_setopt(m, CURLMOPT_PIPELINING, CURLPIPE_MULTIPLEX);
}
~~~

# HISTORY

The multiplex support bit was added in 7.43.0. HTTP/1 Pipelining support was
disabled in 7.62.0.

Since 7.62.0, **CURLPIPE_MULTIPLEX** is enabled by default.

Before that, default was **CURLPIPE_NOTHING**.

# %AVAILABILITY%

# RETURN VALUE

Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.