mod_deflate Supported Encodings for Compression

Question

It seems to me, that mod_deflate in Apache 2.2 will always return:

Content-Encoding: gzip

and never:

Content-Encoding: deflate

It was explained to me, that although there may be a deflate algorithm, mod_deflate is named after a file-format, in which the algorithm could be any of:

gzip, bzip. pkzip

Of those three, mod_deflate provides gzip.

It seems as though gzip is the most popular and widely-supported algorithm in web browsers, but I know some web servers and proxies do return Content-Encoding: deflate.

Aside from the confusion of the module's name, it true that mod_deflate will only return Content-Encoding: gzip?

Thank you.

Answer 1

I believe both the encodings compress to the same extent. Unless there's some special purpose for which you need only deflate, I don't see any reason why you specifically want deflate to be used instead of gzip.

There may be some performance differences. If yes, please enlighten me.

Answer 2

Yes. From what I've read in the Apache docs and from people in the Apache httpd project i've talked to, mod_deflate will only ever return gzipped content.