title: Why does an HTML 5 video tag not work for using a YouTube video as source?
body: <p>Using Chrome, if I look into a YouTube's page, such as <a href="https://www.youtube.com/watch?v=S5CjKEFb-sM" rel="nofollow">https://www.youtube.com/watch?v=S5CjKEFb-sM</a> then I will see that the following HTML5 is responsible for showing the video:</p>
  
  <pre><code>&lt;video class="video-stream html5-main-video" 
      style="width: 640px; height: 360px; left: 0px; top: 0px; 
             transform: none;" 
      src="blob:https%3A//www.youtube.com/71c0fdee-822a-4b58-9ed5-fef443f2e7fd"&gt;
  &lt;/video&gt;
  </code></pre>
  
  <p>to verify, I set the CSS to <code>display: none</code> and the video disappeared, so that should verify that this is the code for showing the video.  Now if I make a file on my hard drive as <code>try.html</code>:</p>
  
  <pre><code>&lt;DOCTYPE html&gt;
  &lt;video class="video-stream html5-main-video" 
      style="width: 640px; height: 360px; left: 0px; top: 0px; 
             transform: none;" 
      src="blob:https%3A//www.youtube.com/71c0fdee-822a-4b58-9ed5-fef443f2e7fd"&gt;
  &lt;/video&gt;
  </code></pre>
  
  <p>That is, just the <code>DOCTYPE</code> together with that <code>&lt;video&gt;</code> tag, and then open this <code>try.html</code> file using Chrome, I don't see anything.</p>
  
  <p>I understand that the suggested embedding method as suggested by YouTube is by an <code>iframe</code>, but I wonder why <code>try.html</code> doesn't work, and how to make it work?  Related is, what is the <code>blob:https%3A</code> part... if I use the developer tool to "Open Link in a New Tab", then nothing will show and how to make it show? (both URLs blob:https%3A//www.youtube.com/a5837a85-ca81-48dc-99b8-48e69a9b4f64 and <a href="https://www.youtube.com/a5837a85-ca81-48dc-99b8-48e69a9b4f64" rel="nofollow">https://www.youtube.com/a5837a85-ca81-48dc-99b8-48e69a9b4f64</a> do not work).</p>