title: YouTube metadata not validating on Twitter
body: <p>I have a <a href="https://www.youtube.com/WanderingDMs" rel="nofollow noreferrer">YouTube channel</a>, for which almost all of the metadata cards fail to <a href="https://cards-dev.twitter.com/validator" rel="nofollow noreferrer">validate on Twitter</a>. Therefore, when one of our video links get posted to Twitter, preview images and descriptions fail to appear. </p>
  
  <p>Looking at the page source from YouTube, we can see that the videos that do validate have the following Twitter card meta tags, while the non-validating ones do not:</p>
  
  <pre><code>&lt;meta name="twitter:player" content="https://www.youtube.com/embed/JkZ79cUy8UQ?list=PLiclN_BSxoe_K-gnfV7CCG0FTVGl5OX_W"&gt;
  &lt;meta name="twitter:player:width" content="1280"&gt;
  &lt;meta name="twitter:player:height" content="720"&gt;
  </code></pre>
  
  <p>I've come up totally empty from online searches for how to manually edit the YouTube metadata cards. If I test <em>other</em> people's YouTube videos, then I have yet to find one that fails to validate on Twitter. </p>
  
  <p>How can I fix these missing meta twitter:player tags on our YouTube videos, so that our YouTube links will validate on Twitter (and thus show preview images)?</p>