title: Improve YouTube thumbnail quality?
body: <p>YouTube thumbnails are appearing terrible when embedded in a webpage via the iFrame code. Once the video starts playing, the quality looks absolutely fine.</p>
  
  <p>Here's an example video:
  <a href="http://jsfiddle.net/x5829/" rel="noreferrer">http://jsfiddle.net/x5829/</a></p>
  
  <p><strong>Before Playing - Bad Quality Thumbnail</strong>
  <img src="https://i.stack.imgur.com/CGkDd.png" alt="YouTube Embedded iFrame Bad Quality Thumbnail"></p>
  
  <p><strong>While Playing - Good Quality</strong>
  <img src="https://i.stack.imgur.com/fGXlL.png" alt="YouTube Embedded iFrame Good Quality"></p>
  
  <p>For whatever reason, it seems to be using the <a href="http://i1.ytimg.com/vi/xzUumjHL5zE/hqdefault.jpg" rel="noreferrer">hqdefault.jpg</a> quality image, rather than the <a href="http://i1.ytimg.com/vi/xzUumjHL5zE/maxresdefault.jpg" rel="noreferrer">maxresdefault.jpg</a> which would be far greater quality.</p>
  
  <p>I've tried increasing the iFrame dimensions to <code>1280x720</code>, and even higher, and nothing seems to make a difference.</p>
  
  <p>Can anything be done, perhaps with the JavaScript API, to force the thumbnail quality to use? All the videos we use will be 720p, guaranteed.</p>
  
  <p>As a final note (I don't think this is important), we're uploading the video using the YouTube API (V3), then setting the thumbnail via the API. But the same thing happens when using an auto-generated thumbnail chosen by YouTube.</p>
  
  <p><strong>Edit -</strong> I wondered if this would improve with time, thought maybe YouTube would optimise it over say 24 hours, but several days later it's still the same.</p>
  
  <p><strong>Edit 2 -</strong> As far as I'm aware, the iFrame is still Google's "recommended" method of embedding videos on a site, so that they'll work on mobile devices as well.</p>