CURLOPT_SUPPRESS_CONNECT_HEADERS(3) Introduction to Library Functions

NAME

CURLOPT_SUPPRESS_CONNECT_HEADERS - suppress proxy CONNECT response
headers

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SUPPRESS_CONNECT_HEADERS, long onoff);

DESCRIPTION

When CURLOPT_HTTPPROXYTUNNEL(3) is used and a CONNECT request is
made, suppress proxy CONNECT response headers from the user callback
functions CURLOPT_HEADERFUNCTION(3) and CURLOPT_WRITEFUNCTION(3).

Proxy CONNECT response headers can complicate header processing since
it is essentially a separate set of headers. You can enable this
option to suppress those headers.

For example let's assume an HTTPS URL is to be retrieved via CONNECT.
On success there would normally be two sets of headers, and each
header line sent to the header function and/or the write function.
The data given to the callbacks would look like this:

HTTP/1.1 200 Connection established
{headers}
...

HTTP/1.1 200 OK
Content-Type: application/json
{headers}
...

{body}
...

However by enabling this option the CONNECT response headers are
suppressed, so the data given to the callbacks would look like this:

HTTP/1.1 200 OK
Content-Type: application/json
{headers}
...

{body}
...

DEFAULT

0

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

curl_easy_setopt(curl, CURLOPT_HEADER, 1L);
curl_easy_setopt(curl, CURLOPT_PROXY, "http://proxy.example:3128");
curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
curl_easy_setopt(curl, CURLOPT_SUPPRESS_CONNECT_HEADERS, 1L);

curl_easy_perform(curl);

/* always cleanup */
curl_easy_cleanup(curl);
}
}

AVAILABILITY

Added in curl 7.54.0

RETURN VALUE

CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.

SEE ALSO

CURLOPT_HEADER(3), CURLOPT_HTTPPROXYTUNNEL(3), CURLOPT_PROXY(3)

libcurl 2026-01-08
CURLOPT_SUPPRESS_CONNECT_HEADERS(3)