anchor.diff:             ;; a valid URL:
              (or (not (http-p (quri:uri-scheme url)))
                  (and
  -                ;; "http://" does not have a host.
  +                ;; "http:/https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xml/" does not have a host.
                   ;; A valid URL may have an empty domain, e.g. http://192.168.1.1.
                   (quri:uri-host url)
                   (or
  
positive.code:              "soap.beep" "soap.beeps" "stun" "stuns" "tag" "tel" "telnet" "tftp"
               "thismessage" "tip" "tn3270" "turn" "turns" "tv" "urn" "vemmi" "vnc" "ws" "wss"
               "xcon" "xcon-userid" "xmlrpc.beep" "xmlrpc.beeps" "xmpp" "z39.50r" "z39.50s"))
           (valid-schemes (append nyxt-schemes iana-schemes))
           (url (ignore-errors (quri:uri url))))
      (flet ((valid-scheme-p (scheme)
               (find scheme valid-schemes :test #'string=))
  
negative.code:   "Return non-nil when URL is a valid URL.
  The domain name existence is verified only if CHECK-DNS-P is T. Domain
  name validation may take significant time since it looks up the DNS."
    (let* ((nyxt-schemes (cons "javascript" (alex:hash-table-keys *schemes*)))
           ;; List of URI schemes: https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
           ;; Last updated 2020-08-26.
           (iana-schemes
             '("aaa" "aaas" "about" "acap" "acct" "cap" "cid" "coap" "coap+tcp" "coap+ws"
               "coaps" "coaps+tcp" "coaps+ws" "crid" "data" "dav" "dict" "dns" "example" "file"
  