mod_gzip

mod_gzip is an external extension module for the Apache HTTP Server v1 and v2.

It allows using the Gzip compression method for a significant reduction of the volume of web page content served over the HTTP protocol.

mod_gzip can be compiled into Apache as either a static or dynamic module.

Compatibility

It is possible to check a server to see if it is sending out compressed data, and compression compatibility of a browser for example here.

When textual content is compressed using mod_gzip, it should maintain its MIME-type, according to their recommended media type:

  • HTML: text/html
  • XHTML: application/xhtml+xml
  • CSS: text/css
  • JavaScript: application/x-javascript

One of the earliest Apache 1.3 versions introduced some internal function for regular expression evaluation. This function is used by mod_gzip (for evaluating the filter rules), therefore mod_gzip would not work together with Apache 1.2.x or earlier versions.[1]

Compatibility between Apache 1.3.x and mod_gzip 1.3.y is granted in general: the Apache 1.3 API doesn't change any more, mod_gzip would even work together with very old Apache 1.3 versions.

Some alternatives

The mod_deflate module is similar to mod_gzip, but usable only with Apache v2. Early versions of mod_deflate provided lesser amount of compression than mod_gzip.[2] Starting with Apache 2.0.45, the compression level of mod_deflate is configurable using the DeflateCompressionLevel directive, so this difference disappeared.

A mod_gz module was independently developed by Ian Holsman. This module implements a gzip compression filter for Apache 2.0, providing similar functionality to mod_gzip. One important difference between the two modules is that mod_gzip includes its own gzip implementation, whereas mod_gz relies on an external zlib library.

In PHP similar effect achievable for the output of PHP scripts with:

CherryPy offers the Gzip filter,[3] which uses the zlib module of Python standard library.

License

The mod_gzip module licensed with Apache License.

History

Module level content compression for Apache started with mod_gzip, written by Kevin Kiley and Konstantin Balashow[4] in autumn 2000, documented by Michael Schröpl,[5][6] published by Remote Communications Inc. (RCI).[7] RCI was purchased by HyperSpace Communications, RCI released the code into the public domain.[8]

The developers of the Apache 2.0.x servers have included the mod_deflate module in the codebase for the server to perform a similar GZIP-encoding function. mod_gzip remained external extension module.

See also

Notes
  1. mod_gzip requires Apache 1.3+
  2. Comparison of mod_deflate and mod_gzip
  3. "CherryPy offers the Gzip filter". Archived from the original on 2005-02-12. Retrieved 2009-10-11.
  4. Cranstone, Peter (2000-10-17). "WebReference Featured Interview". www.webreference.com. Retrieved 2017-07-02.
  5. "mod_gzip written by Michael Schröpl". Archived from the original on 2008-09-17. Retrieved 2009-10-11.
  6. mod_gzip written in autumn 2000
  7. RCI had originally published mod_gzip
  8. RCI released the code into the public domain
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