NAME

       CURLOPT_HTTP_VERSION - specify HTTP protocol version to use

SYNOPSIS

       #include <curl/curl.h>

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

DESCRIPTION

       Pass version a long, set to one of the values described below. They ask libcurl to use the
       specific HTTP versions. This is not sensible to do unless you have a good reason. You have
       to set this option if you want to use libcurl's HTTP/2 support.

       Note  that  the HTTP version is just a request. libcurl will still prioritize to re-use an
       existing connection so it might then re-use a connection using a HTTP version you  haven't
       asked for.

       CURL_HTTP_VERSION_NONE
              We  don't  care  about  what version the library uses. libcurl will use whatever it
              thinks fit.

       CURL_HTTP_VERSION_1_0
              Enforce HTTP 1.0 requests.

       CURL_HTTP_VERSION_1_1
              Enforce HTTP 1.1 requests.

       CURL_HTTP_VERSION_2_0
              Attempt HTTP 2 requests. libcurl will fall back to HTTP 1.1  if  HTTP  2  can't  be
              negotiated with the server. (Added in 7.33.0)

              The  alias  CURL_HTTP_VERSION_2  was  added  in 7.43.0 to better reflect the actual
              protocol name.

       CURL_HTTP_VERSION_2TLS
              Attempt HTTP 2 over TLS (HTTPS) only. libcurl will fall back to HTTP 1.1 if HTTP  2
              can't  be  negotiated  with  the HTTPS server. For clear text HTTP servers, libcurl
              will use 1.1. (Added in 7.47.0)

       CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE
              Issue non-TLS HTTP requests using HTTP/2  without  HTTP/1.1  Upgrade.  It  requires
              prior  knowledge that the server supports HTTP/2 straight away. HTTPS requests will
              still do HTTP/2 the standard way  with  negotiated  protocol  version  in  the  TLS
              handshake. (Added in 7.49.0)

DEFAULT

       CURL_HTTP_VERSION_NONE

PROTOCOLS

       HTTP

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         CURLcode ret;
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
         curl_easy_setopt(curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2TLS);
         ret = curl_easy_perform(curl);
         if(ret == CURLE_HTTP_RETURNED_ERROR) {
           /* a HTTP response error problem */
         }
       }

AVAILABILITY

       Along with HTTP

RETURN VALUE

       Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.

SEE ALSO

       CURLOPT_SSLVERSION(3), CURLOPT_HTTP200ALIASES(3),