---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_PRE_PROXY
Section: 3
Source: libcurl
See-also:
  - CURLOPT_HTTPPROXYTUNNEL (3)
  - CURLOPT_PROXY (3)
---

# NAME

CURLOPT_PRE_PROXY - pre-proxy host to use

# SYNOPSIS

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

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PRE_PROXY, char *preproxy);
~~~

# DESCRIPTION

Set the *preproxy* to use for the upcoming request. The parameter should be a
char * to a null-terminated string holding the hostname or dotted numerical IP
address. A numerical IPv6 address must be written within [brackets].

To specify port number in this string, append :[port] to the end of the host
name. The proxy's port number may optionally be specified with the separate
option CURLOPT_PROXYPORT(3). If not specified, libcurl defaults to using
port 1080 for proxies.

A pre proxy is a SOCKS proxy that curl connects to before it connects to the
HTTP(S) proxy specified in the CURLOPT_PROXY(3) option. The pre proxy
can only be a SOCKS proxy.

The pre proxy string should be prefixed with [scheme]:// to specify which kind
of socks is used. Use socks4://, socks4a://, socks5:// or socks5h:// (the last
one to enable socks5 and asking the proxy to do the resolving, also known as
*CURLPROXY_SOCKS5_HOSTNAME* type) to request the specific SOCKS version to
be used. Otherwise SOCKS4 is used as default.

Setting the pre proxy string to "" (an empty string) explicitly disables the
use of a pre proxy.

The application does not have to keep the string around after setting this
option.

# DEFAULT

Default is NULL, meaning no pre proxy is used.

When you set a hostname to use, do not assume that there is any particular
single port number used widely for proxies. Specify it!

# PROTOCOLS

All except file://. Note that some protocols do not work well over proxy.

# EXAMPLE

~~~c
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/file.txt");
    curl_easy_setopt(curl, CURLOPT_PRE_PROXY, "socks4://socks-proxy:1080");
    curl_easy_setopt(curl, CURLOPT_PROXY, "http://proxy:80");
    curl_easy_perform(curl);
  }
}
~~~

# AVAILABILITY

Added in 7.52.0

# RETURN VALUE

Returns CURLE_OK if proxies are supported, CURLE_UNKNOWN_OPTION if not, or
CURLE_OUT_OF_MEMORY if there was insufficient heap space.