CURLOPT_SSL_ENABLE_NPN

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_NPN, long npn);

Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This option enables/disables NPN in the SSL handshake (if the SSL backend libcurl is built to use supports it), which can be used to negotiate http2.

1, enabled

HTTP

CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
  curl_easy_setopt(curl, CURLOPT_SSL_ENABLE_NPN, 1L);
  ret = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

Added in 7.36.0

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_SSL_ENABLE_ALPN(3), CURLOPT_SSL_OPTIONS(3),