CURLOPT_HTTP_VERSION (3) - Linux Man Pages
CURLOPT_HTTP_VERSION: specify HTTP protocol version to use
NAMECURLOPT_HTTP_VERSION - specify HTTP protocol version to use
DESCRIPTIONPass version a long, set to one of the values described below. They force 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.
- We don't care about what version the library uses. libcurl will use whatever it thinks fit.
- Enforce HTTP 1.0 requests.
- Enforce HTTP 1.1 requests.
- Attempt HTTP 2.0 requests. libcurl will fall back to HTTP 1.x if HTTP 2.0 can't be negotiated with the server.