diff --git a/source b/source
index 639b5eb2735..3d0deda8280 100644
--- a/source
+++ b/source
@@ -2660,10 +2660,10 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
     <ul class="brief">
      <li><dfn data-x="concept-host" data-x-href="https://url.spec.whatwg.org/#concept-host">host</dfn></li>
+     <li><dfn data-x-href="https://url.spec.whatwg.org/#host-registrable-domain">registrable domain</dfn></li>
      <li><dfn data-x="concept-domain" data-x-href="https://url.spec.whatwg.org/#concept-domain">domain</dfn></li>
      <li><dfn data-x-href="https://url.spec.whatwg.org/#concept-ipv4">IPv4 address</dfn></li>
      <li><dfn data-x-href="https://url.spec.whatwg.org/#concept-ipv6">IPv6 address</dfn></li>
-     <li><dfn data-x-href="https://url.spec.whatwg.org/#host-same-site">same site</dfn></li>
      <li><dfn data-x-href="https://url.spec.whatwg.org/#concept-url">URL</dfn></li>
      <li><dfn data-dfn-for="url" data-x="concept-url-origin" data-x-href="https://url.spec.whatwg.org/#concept-url-origin">Origin</dfn> of URLs</li>
      <li><dfn data-x-href="https://url.spec.whatwg.org/#syntax-url-absolute">Absolute URL</dfn></li>
@@ -79672,8 +79672,29 @@ interface <dfn>BarProp</dfn> {
 
    <li><p>If <var>host</var> is failure, then return false.</p></li>
 
-   <li><p>Return true if <var>host</var> is <span>same site</span> with <var>originalHost</var>, and
-   false otherwise.</p></li>
+   <li>
+    <p>If <var>host</var> does not <span data-x="host equals">equal</span> <var>originalHost</var>,
+    then:</p>
+
+    <ol>
+     <li>
+      <p>If <var>host</var> or <var>originalHost</var> is not a <span
+      data-x="concept-domain">domain</span>, then return false.</p>
+
+      <p class="note">This excludes <span data-x="concept-host">hosts</span> that are an <span>IPv4
+      address</span> or an <span>IPv6 address</span>.</p>
+     </li>
+
+     <li><p>If <var>host</var>, prefixed by a U+002E FULL STOP (.), does not exactly match the end
+     of <var>originalHost</var>, then return false.</p></li>
+     <!-- This seems okay, but does pretend hosts are strings which URL does not. -->
+
+     <li><p>If <var>host</var>'s <span>registrable domain</span> is null, then return false. <ref
+     spec=URL></p></li>
+    </ol>
+   </li>
+
+   <li><p>Return true.</p></li>
   </ol>
 
   <p>The <dfn><code data-x="dom-document-domain">domain</code></dfn> attribute's getter must run
@@ -120277,6 +120298,10 @@ INSERT INTERFACES HERE
    <dt id="refsPRESENTATION">[PRESENTATION]</dt>
    <dd><cite><a href="https://w3c.github.io/presentation-api/">Presentation API</a></cite>, M. Foltz, D. Röttsches. W3C.</dd>
 
+   <dt id="refsPSL">[PSL]</dt>
+   <dd><cite><a href="https://publicsuffix.org/">Public Suffix List</a></cite>.
+   Mozilla Foundation.</dd>
+
    <dt id="refsREFERRERPOLICY">[REFERRERPOLICY]</dt>
    <dd><cite><a href="https://w3c.github.io/webappsec-referrer-policy/">Referrer Policy</a></cite>, J. Eisinger, E. Stark. W3C.</dd>