Why do real-world servers prefer gzip over deflate encoding?

user_3779 0
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We already know deflate encoding is a winner over gzip with respect to speed of encoding, decoding and compression size.

So why do no large sites (that I can find) send it (when I use a browser that accepts it)?

Yahoo claims deflate is "less effective". Why?

I maintain HTTP server software that prefers deflate, so I'd like to know if there's some really good reason not to continue doing so.

deflate compression gzip encoding http
6 Answers

From my minimal testing it appears most HTTPds either:

  1. don't support deflate on-the-fly: Apache's mod_deflate (a suprise), GWS
  2. or prefer to send gzip: IIS, lighttpd's mod_compress

So to send deflate on the most popular server (Apache), you must maintain pre-encoded files and use mod_negotiate (you might even have to use type-maps to prefer deflate).

I'd guess, due to this hassle, deflate is just rarely used, and therefore bugs are more likely to exist in client deflate support than in gzip support.

user_37790

As far as I know (disclaimer: and I'm not an expert here, just what I've heard), gzip uses the same algorithm as deflate but it has more header stuff that make it have a larger size (relative to deflate). However, I think deflate is supported by less clients and proxies.

user_337080

I wondered the same thing :). I think it might be to do with compatibility of older (possibly ancient) browsers. I read somewhere that older browsers are more likely to creep out at deflated content that mod_gzipped in certain instances(?) but googling this led me to conclude that it's probably best to stop googling it.

user_703930

ActionScript 3 has native deflate support, but for gzip you need to use an external library

user_1650710
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