title: Deflate compression browser compatibility and advantages over GZIP
body: <hr>
  
  <h2>UPDATE Feb 10 2012:</h2>
  
  <p>zOompf has completed some very thorough research on this very topic <a href="http://zoompf.com/blog/2012/02/lose-the-wait-http-compression" rel="noreferrer">here</a>. It trumps any findings below.
  <br/></p>
  
  <hr>
  
  <h2>UPDATE Sept 11 2010:</h2>
  
  <h2>A testing platform has been created for this <a href="http://www.vervestudios.co/projects/compression-tests/" rel="noreferrer">here</a></h2>
  
  <p><br/></p>
  
  <hr>
  
  <p><br/>
  HTTP 1.1 definitions of GZIP and DEFLATE (zlib) for some background information:</p>
  
  <p>" 'Gzip' is the gzip format, and <strong>'deflate' is the zlib format</strong>. They
  should probably have called the second one 'zlib' instead to avoid
  confusion with the raw deflate compressed data format. While the HTTP
  1.1 RFC 2616 correctly points to the zlib specification in RFC 1950
  for the 'deflate' transfer encoding, <strong>there have been reports of
  servers and browsers that incorrectly produce or expect raw deflate
  data per the deflate specification in RFC 1951, <em>most notably
  Microsoft products</em></strong>. So even though the 'deflate' transfer encoding using the
  zlib format would be the more efficient approach (<em>and in fact exactly
  <strong>what the zlib format was designed for</em></strong>), using the 'gzip' transfer
  encoding is probably more reliable due to an unfortunate choice of
  name on the part of the HTTP 1.1 authors." (source: <a href="http://www.gzip.org/zlib/zlib_faq.html" rel="noreferrer">http://www.gzip.org/zlib/zlib_faq.html</a>)</p>
  
  <p>So, my question: if I send RAW deflate data with NO zlib wrapper (or gzip,
  for that matter) are there any modern browsers (e.g., IE6 and up, FF,
  Chrome, Safari, etc) that can NOT understand the raw deflate
  compressed data (assuming HTTP request header "Accept-Encoding" contains "deflate")?</p>
  
  <p>Deflate data will ALWAYS be a few bytes smaller than GZIP.</p>
  
  <p>If all these browsers can successfully decode the data, what
  downsides are there to sending RAW deflate instead of zlib?</p>
  
  <p><br /><br /></p>
  
  <h2>UPDATE Sept 11 2010:</h2>
  
  <h2>A testing platform has been created for this <a href="http://www.vervestudios.co/projects/compression-tests/" rel="noreferrer">here</a></h2>