title: How can I determine the exact value used for a media query?
body: <p>When using</p>
  
  <pre><code>&lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
  </code></pre>
  
  <p>I can use css</p>
  
  <pre><code>@media all and (min-width:400px) { ... }
  </code></pre>
  
  <p>or javascript</p>
  
  <pre><code>if(window.matchMedia("(min-width: 400px)").matches)
  </code></pre>
  
  <p>to style / build the page according to screen threshholds.</p>
  
  <p>How can I determine the exact value of the width (other than narrowing it down via javascript)?</p>
  
  <p>Some testing indicated that the value used is the same as in <code>screen.width</code>. Is that true? Under every circumstance?</p>