CURLOPT_PROXY(3) Library Functions Manual CURLOPT_PROXY(3)

CURLOPT_PROXY - proxy to use

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY, char *proxy);

Set the proxy to use for transfers with this easy handle. 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 (but discouraged) be specified with the separate option CURLOPT_PROXYPORT(3). If not specified, libcurl defaults to using port 1080 for proxies.

The proxy string may be prefixed with [scheme]:// to specify which kind of proxy is used.

HTTP Proxy. Default when no scheme or proxy type is specified.
HTTPS Proxy. (Added in 7.52.0 for OpenSSL and GnuTLS Since 7.87.0, it also works for BearSSL, mbedTLS, rustls, Schannel, Secure Transport and wolfSSL.)

This uses HTTP/1 by default. Setting CURLOPT_PROXYTYPE(3) to CURLPROXY_HTTPS2 allows libcurl to negotiate using HTTP/2 with proxy.

SOCKS4 Proxy.
SOCKS4a Proxy. Proxy resolves URL hostname.
SOCKS5 Proxy.
SOCKS5 Proxy. Proxy resolves URL hostname.

Without a scheme prefix, CURLOPT_PROXYTYPE(3) can be used to specify which kind of proxy the string identifies.

When you tell the library to use an HTTP proxy, libcurl transparently converts operations to HTTP even if you specify an FTP URL etc. This may have an impact on what other features of the library you can use, such as CURLOPT_QUOTE(3) and similar FTP specifics that do not work unless you tunnel through the HTTP proxy. Such tunneling is activated with CURLOPT_HTTPPROXYTUNNEL(3).

Setting the proxy string to "" (an empty string) explicitly disables the use of a proxy, even if there is an environment variable set for it.

A proxy host string can also include protocol scheme (http://) and embedded user + password.

Unix domain sockets are supported for socks proxies since 7.84.0. Set localhost for the host part. e.g. socks5h://localhost/path/to/socket.sock

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

When a proxy is used, the active FTP mode as set with CUROPT_FTPPORT(3), cannot be used.

libcurl respects the proxy environment variables named http_proxy, ftp_proxy, sftp_proxy etc. If set, libcurl uses the specified proxy for that URL scheme. For an "FTP://" URL, the ftp_proxy is considered. all_proxy is used if no protocol specific proxy was set.

If no_proxy (or NO_PROXY) is set, it is the exact equivalent of setting the CURLOPT_NOPROXY(3) option.

The CURLOPT_PROXY(3) and CURLOPT_NOPROXY(3) options override environment variables.

Default is NULL, meaning no 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!

All

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_PROXY, "http://proxy:80");
    curl_easy_perform(curl);
  }
}

Since 7.14.1 the proxy environment variable names can include the protocol scheme.

Since 7.21.7 the proxy string supports the socks protocols as "schemes".

Since 7.50.2, unsupported schemes in proxy strings cause libcurl to return error.

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

CURLOPT_HTTPPROXYTUNNEL(3), CURLOPT_PRE_PROXY(3), CURLOPT_PROXYPORT(3), CURLOPT_PROXYTYPE(3)

2024-05-22 libcurl