title: How does tumblr get the page thumbnail image when posting a link?
body: <p>When I share a link on tumblr, it sometimes will grab the page's blog post image. For example, if I share something like:</p>
  
  <pre><code>http://www.smartpassiveincome.com/income-reports/my-may-2016-monthly-income-report/
  </code></pre>
  
  <p>It'll grab this image for it's thumbnail: </p>
  
  <p><a href="http://cdn.smartpassiveincome.com/wp-content/uploads/2016/03/Income-Reports-legacy-posts.jpg" rel="nofollow">http://cdn.smartpassiveincome.com/wp-content/uploads/2016/03/Income-Reports-legacy-posts.jpg</a></p>
  
  <p>How do you make tumblr grab the image? Is there some meta tag you need to include?</p>
  
  <p>Searching the source code this image appears three times:</p>
  
  <pre><code>&lt;meta property="og:image" content="http://cdn.smartpassiveincome.com/wp-content/uploads/2016/03/Income-Reports-legacy-posts.jpg"/&gt;
  
  &lt;meta name="twitter:image" content="http://cdn.smartpassiveincome.com/wp-content/uploads/2016/03/Income-Reports-legacy-posts.jpg"/&gt;
  
  &lt;header style="background-image: url('http://cdn.smartpassiveincome.com/wp-content/uploads/2016/03/Income-Reports-legacy-posts.jpg')"&gt;
  </code></pre>
  
  <p>Does anyone know which one it uses and could explain what the process for choosing how to grab the image is?</p>
  
  <p>The original page is: <a href="http://www.patchesoft.com/learning-linux-how-to-find-what-version-of-linux-youre-running-command-uname-and-lsb_release/" rel="nofollow">http://www.patchesoft.com/learning-linux-how-to-find-what-version-of-linux-youre-running-command-uname-and-lsb_release/</a></p>
  
  <p>But when I post it into Tumblr, it doesn't grab the featured image.</p>