what is the received header when host header value with curl is not set

Question

I am sending a curl request but i am not setting the host header explicitly. What will be the host header as received by the remote url? Will it be my site's domain, or will be automatically be the domain of the remote url?

Answer 1

The Host header is automatically set based on the URL of your request.

And it's by definition the Internet hostname of the remote URL.

Answer 2

If you don't set it, remote server won't receive it. If you send the request as HTTP/1.1, the server should consider it a malformed request, so you'll probably receive an error code.

However, if the backend (e.g. Apache) performs some processing before passing the request to the script, it may set something according to its own logic.