title: What is the "Upgrade-Insecure-Requests" HTTP header?
body: <p>I made a POST request to a HTTP (non-HTTPS) site, inspected the request in Chrome's Developer Tools, and found that it added its own header before sending it to the server:</p>
  
  <pre><code>Upgrade-Insecure-Requests: 1
  </code></pre>
  
  <p>After doing a search on <code>Upgrade-Insecure-Requests</code>, I can only find <a href="http://www.w3.org/TR/upgrade-insecure-requests/" rel="noreferrer">information</a> about the server sending <a href="https://googlechrome.github.io/samples/csp-upgrade-insecure-requests/" rel="noreferrer">this</a> header:</p>
  
  <pre><code>Content-Security-Policy: upgrade-insecure-requests
  </code></pre>
  
  <p>This seems related, but still very different since in my case, the CLIENT is sending the header in the <em>Request</em>, whereas all the information I've found is concerning the SERVER sending the related header in a <em>Response</em>.</p>
  
  <hr>
  
  <p>So why is Chrome (44.0.2403.130 m) adding <code>Upgrade-Insecure-Requests</code> to my request and what does it do?</p>
  
  <hr>
  
  <h1>Update 2016-08-24:</h1>
  
  <p>This header has since been added as a <a href="https://www.w3.org/TR/2015/CR-upgrade-insecure-requests-20151008/#preference" rel="noreferrer">W3C Candidate Recommendation</a> and is now officially recognized.</p>
  
  <p>For those who just came across this question and are confused, the <a href="https://stackoverflow.com/a/32003517/2891365">excellent answer</a> by Simon East explains it well.</p>
  
  <p>The <code>Upgrade-Insecure-Requests: 1</code> header used to be <code>HTTPS: 1</code> <a href="https://www.w3.org/TR/2015/WD-upgrade-insecure-requests-20150424/#preference" rel="noreferrer">in the previous W3C Working Draft</a> and was renamed <strong><em>quietly</em></strong> by Chrome before the change became officially accepted.</p>
  
  <p>(This question was asked during this transition when there were no official documentation on this header and Chrome was the only browser that sent this header.)</p>