CURLOPT_SSL_ENABLE_NPN(3) Library Functions Manual CURLOPT_SSL_ENABLE_NPN(3)

CURLOPT_SSL_ENABLE_NPN - use NPN

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_NPN, long npn);

Deprecated in 7.86.0. Setting this option has no function.

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

All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

All TLS backends support this option.

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

Added in 7.36.0. Deprecated in 7.86.0.

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

CURLOPT_SSL_ENABLE_ALPN(3), CURLOPT_SSL_OPTIONS(3)

2024-05-22 libcurl