title: What is twitter:domain good for?
body: <p>I'm currently trying the <a href="https://dev.twitter.com/docs/cards/validation/validator" rel="noreferrer">Twitter Card Validator</a> for <a href="http://martin-thoma.com/jekyll-and-git/" rel="noreferrer">my website</a>.</p>
  
  <p>I did not set <code>twitter:domain</code>, because the help text shows</p>
  
  <pre><code>RESTRICTED - twitter:domain will be automatically generated from your card's URL.
  
  Not required
  </code></pre>
  
  <p>But I've just wondered if I should set it anyway. </p>
  
  <p><strong>What would be the effect when I set twitter:domain? To which value should I set it? Should I set it at all?</strong> </p>
  
  <p>(I guess <code>martin-thoma.com</code>, but it might also be <code>http://martin-thoma.com</code> or <code>martin-thoma.com/</code>.)</p>
  
  <p><strong>Answers that don't cite a reliable source are note acceptable!</strong></p>