title: How to force high quality thumbnails for YouTube Player API iframe Embeds?
body: <p>The thumbnails looked fine for over a year, but suddenly became blurry.
  The thumbnail that appears on page load looks correct, but anytime a new thumbnail is displayed using 'player.cueVideoById', it looks very blurry.</p>
  
  <p>There is no mention in the documentation of how to control the thumbnail quality (only video quality settings, such as 'setPlaybackQuality' are available). The documentation: <a href="https://developers.google.com/youtube/iframe_api_reference">https://developers.google.com/youtube/iframe_api_reference</a></p>
  
  <p>How can I force high quality thumbnail images?</p>