CURLOPT_HTTP_VERSION(3) curl_easy_setopt options CURLOPT_HTTP_VERSION(3)
NAME
CURLOPT_HTTP_VERSION - 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.
Note that the HTTP version is just a request. libcurl will still prior-
itize to re-use an existing connection so it might then re-use a con-
nection using a HTTP version you have not asked for.
CURL_HTTP_VERSION_NONE
We do not 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 cannot be negotiated with the server. (Added in 7.33.0)
The alias CURL_HTTP_VERSION_2 was added in 7.43.0 to better re-
flect 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 cannot 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 Up-
grade. 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 hand-
shake. (Added in 7.49.0)
CURL_HTTP_VERSION_3
(Added in 7.66.0) Setting this value will make libcurl attempt
to use HTTP/3 directly to server given in the URL. Note that
this cannot gracefully downgrade to earlier HTTP version if the
server does not support HTTP/3.
For more reliably upgrading to HTTP/3, set the preferred version
to something lower and let the server announce its HTTP/3 sup-
port via Alt-Svc:. See CURLOPT_ALTSVC(3).
DEFAULT
Since curl 7.62.0: CURL_HTTP_VERSION_2TLS
Before that: CURL_HTTP_VERSION_1_1
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) {
/* an 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), CURLOPT_HTTP09_AL-
LOWED(3), CURLOPT_ALTSVC(3)
libcurl 7.81.0 November 26, 2021 CURLOPT_HTTP_VERSION(3)
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