title: Why is Chrome sending sec-ch-ua and sec-ch-ua-mobile request headers although "Experimental Web Platform features" are disabled
body: <p>I have the situation with Chrome, tested with <code>87.0.4280.88</code>, that in some cases Chrome will send <code>sec-ch-ua</code> and <code>sec-ch-ua-mobile</code> request headers, although <code>chrome://flags/#enable-experimental-web-platform-features</code> is set to &quot;disabled&quot;.</p>
  <p>For instance:</p>
  <pre><code>sec-ch-ua: &quot;Google Chrome&quot;;v=&quot;87&quot;, &quot; Not;A Brand&quot;;v=&quot;99&quot;, &quot;Chromium&quot;;v=&quot;87&quot;
  sec-ch-ua-mobile: ?0
  </code></pre>
  <p>When this happens, the only way to get rid of these headers is to start Chrome with the parameter <code>--disable-features=UserAgentClientHint</code>.</p>
  <p>Does someone have an explanation for this? As far as I understand, these features are still experimental and the specification in progress (<a href="https://wicg.github.io/ua-client-hints/" rel="noreferrer">https://wicg.github.io/ua-client-hints/</a>).</p>