title: Windows 8 apparently removes content-encoding header from compressed HTTP responses
body: <p>I'm not completely sure whether this belongs on SO, but I don't know where else to ask.</p>
  
  <p>While I was checking the loading speed of a web app of mine I noticed that apparently no HTTP response (no matter what type - html, css, js) is gzip/deflate compressed. That is, no response header like "Content-Encoding: gzip" is present in any request and the browser reports that the resource is not compressed.</p>
  
  <ul>
  <li>tested and confirmed in multiple browsers (IE10, FF 17, Chrome 23, Opera 12.10, Safari 5.x)</li>
  <li>tested and confirmed on two machines running Windows 8 Pro</li>
  <li>double checked with Fiddler - the response is not compressed and does not contain a content-encoding header</li>
  <li>this doesn't only happen for my web apps, <em>no</em> other web site  I tested appears to send compressed responses (according to the browser)</li>
  <li>on Windows 7 the responses arrive compressed and with all headers</li>
  <li>HTTPS responses <em>are</em> compressed</li>
  </ul>
  
  <p>Here's an example of the response headers (note the lack of the content-encoding header):
  <img src="https://i.stack.imgur.com/ZyDW3.png" alt="response headers on client machine"></p>
  
  <p>I also checked the server side. The server is running Windows Server 2008 R2/IIS 7.5. I used Failed Request Tracing to find out what the server is sending. The resource appears to be compressed:</p>
  
  <p><img src="https://i.stack.imgur.com/dZN9i.png" alt="server side compression"></p>
  
  <p>Also, the server seems to send the proper headers:</p>
  
  <p><img src="https://i.stack.imgur.com/UXowb.png" alt="compression headers"></p>
  
  <p>My conclusion: it must be Windows 8 who is intervening here. Apparently it modifies HTTP responses. I suppose that Windows 8 is receiving the compressed response, decompresses it, removes the content-encoding header and passes the modified response further down the pipeline.</p>
  
  <p>Now my questions:</p>
  
  <ul>
  <li>Can anybody confirm that Windows 8 modifies HTTP responses and that it works the way I described?</li>
  <li>Is there a way to monitor or even disable this behavior?</li>
  </ul>
  
  <p>Thanks in advance for your answers.</p>
  
  <p>Regards,
  Andre</p>
  
  <hr>
  
  <p>Update:
  I used Wireshark to see what arrives at the client. As I expected the resources are compressed and the content-encoding header is still present. The image below shows the wireshark protocol and in the bottom right the response as received by Chrome.</p>
  
  <p><img src="https://i.stack.imgur.com/x0Gff.png" alt="wireshark"></p>
  
  <p>This confirms my assumption that Windows 8 is intervening.</p>