CURLOPT_SSL_ENABLE_NPN(3) Library Functions Manual CURLOPT_SSL_ENABLE_NPN(3)
NAME
CURLOPT_SSL_ENABLE_NPN - use NPN
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_NPN, long npn);
DESCRIPTION
Deprecated. 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.
DEFAULT
1, enabled
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) {
CURLcode result;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_SSL_ENABLE_NPN, 1L);
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
DEPRECATED
Deprecated since 7.86.0
AVAILABILITY
Added in curl 7.36.0
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_SSL_ENABLE_ALPN(3), CURLOPT_SSL_OPTIONS(3)
libcurl 2026-03-23 CURLOPT_SSL_ENABLE_NPN(3)
curl 8.19.0 - Generated Tue Mar 31 13:25:53 CDT 2026