Why people use `rel="noopener noreferrer"` instead of just `rel="noreferrer"` : <p>I often see following pattern:</p>

<pre><code>&lt;a href="&lt;external&gt;" target="_blank" rel="noopener noreferrer"&gt;&lt;/a&gt;
</code></pre>

<p>But as far as I see, <code>noreferrer</code> implies the effect of <code>noopener</code>. So why is <code>noopener</code> even needed here?</p>

<p><a href="https://html.spec.whatwg.org/multipage/links.html#link-type-noreferrer" rel="noreferrer">https://html.spec.whatwg.org/multipage/links.html#link-type-noreferrer</a></p>

<blockquote>
  <p><code>&lt;a href="..." rel="noreferrer" target="_blank"&gt;</code> has the same behavior as <code>&lt;a href="..." rel="noreferrer noopener" target="_blank"&gt;</code>.</p>
</blockquote>

<p>Note that <code>noreferrer</code> browser support is strictly wider that one of <code>noopener</code>
<a href="https://caniuse.com/#feat=rel-noreferrer" rel="noreferrer">https://caniuse.com/#feat=rel-noreferrer</a>
<a href="https://caniuse.com/#feat=rel-noopener" rel="noreferrer">https://caniuse.com/#feat=rel-noopener</a></p>
