CURLOPT_HTTP_VERSION man page

## 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

TODO

## AVAILABILITY

Along with HTTP

## RETURN VALUE

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

## SEE ALSO

CURLOPT_SSLVERSION, CURLOPT_HTTP200ALIASES

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