How to just show HTTP headers using wget

Use --server-response -qO /dev/null:

wget --server-response -qO /dev/null [URL]

Example:

wget --server-response -qO /dev/null https://techoverflow.net

Example output:

HTTP/1.1 200 OK
Server: nginx/1.14.0 (Ubuntu)
Date: Mon, 18 Nov 2019 02:15:19 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Accept-Encoding
Set-Cookie: cookielawinfo-checkbox-necessary=yes; expires=Mon, 18-Nov-2019 03:15:18 GMT; Max-Age=3600; path=/
Set-Cookie: cookielawinfo-checkbox-non-necessary=yes; expires=Mon, 18-Nov-2019 03:15:18 GMT; Max-Age=3600; path=/
Link: <https://techoverflow.net/wp-json/>; rel="https://api.w.org/"