=== HTTP code : 200 ===

Response headers
================
HTTP/1.1 301 Moved Permanently
Date: Mon, 29 Jul 2019 02:05:13 GMT
Server: Apache
Location: http://ssdp.org/about/
Vary: Accept-Encoding
Connection: close
Content-Type: text/html; charset=UTF-8

HTTP/1.1 301 Moved Permanently
Date: Mon, 29 Jul 2019 02:05:13 GMT
Server: Apache
Location: https://ssdp.org/about/
Vary: Accept-Encoding
Connection: close
Content-Type: text/html; charset=UTF-8

HTTP/1.1 200 OK
Date: Mon, 29 Jul 2019 02:05:13 GMT
Server: Apache
Link: &lt;https://ssdp.org/wp-json/&gt;; rel=&quot;https://api.w.org/&quot;, &lt;https://ssdp.org/?p=23796&gt;; rel=shortlink
Connection: close
Content-Type: text/html; charset=UTF-8

Request headers
================
HEAD /about/ HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36
Host: ssdp.org
Accept: */*
Referer: https://ssdp.org
Connection: close


Link is valid.