CURLOPT_PROXY_SSLVERSION(3) Introduction to Library Functions

NAME

CURLOPT_PROXY_SSLVERSION - preferred HTTPS proxy TLS version

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_SSLVERSION,
long version);

DESCRIPTION

Pass a long as parameter to control which version of SSL/TLS to
attempt to use when connecting to an HTTPS proxy.

Use one of the available defines for this purpose. The available
options are:

CURL_SSLVERSION_DEFAULT
The default action. This attempts to figure out the remote SSL
protocol version.

CURL_SSLVERSION_TLSv1
TLSv1.x

CURL_SSLVERSION_TLSv1_0
TLSv1.0

CURL_SSLVERSION_TLSv1_1
TLSv1.1

CURL_SSLVERSION_TLSv1_2
TLSv1.2

CURL_SSLVERSION_TLSv1_3
TLSv1.3

The maximum TLS version can be set by using one of the
CURL_SSLVERSION_MAX_ macros below. It is also possible to OR one of
the CURL_SSLVERSION_ macros with one of the CURL_SSLVERSION_MAX_
macros. The MAX macros are not supported for wolfSSL.

CURL_SSLVERSION_MAX_DEFAULT
The flag defines the maximum supported TLS version as TLSv1.2,
or the default value from the SSL library.

CURL_SSLVERSION_MAX_TLSv1_0
The flag defines maximum supported TLS version as TLSv1.0.

CURL_SSLVERSION_MAX_TLSv1_1
The flag defines maximum supported TLS version as TLSv1.1.

CURL_SSLVERSION_MAX_TLSv1_2
The flag defines maximum supported TLS version as TLSv1.2.

CURL_SSLVERSION_MAX_TLSv1_3
The flag defines maximum supported TLS version as TLSv1.3.

DEFAULT

CURL_SSLVERSION_DEFAULT

PROTOCOLS

This functionality affects all TLS based protocols: HTTPS, FTPS,
IMAPS, POP3S, SMTPS etc.

All TLS backends support this option.

EXAMPLE

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

/* ask libcurl to use TLS version 1.0 or later */
curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);

/* Perform the request */
curl_easy_perform(curl);
}
}

HISTORY

CURL_SSLVERSION_* macros became long types in 8.16.0, prior to this
version a long cast was necessary when passed to curl_easy_setopt(3).

AVAILABILITY

Added in curl 7.52.0

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).

SEE ALSO

CURLOPT_HTTP_VERSION(3), CURLOPT_IPRESOLVE(3), CURLOPT_SSLVERSION(3),
CURLOPT_USE_SSL(3)

libcurl 2026-01-08 CURLOPT_PROXY_SSLVERSION(3)