# Mod gzip

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{{Short description|Extension Module}}
{{DISPLAYTITLE:mod_gzip}}
'''mod_gzip''' is an external extension module for the [Apache HTTP Server](/source/Apache_HTTP_Server) v1 and v2.

It allows using the [Gzip](/source/Gzip) compression method for a significant reduction of the volume of web page content served over the [HTTP](/source/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 [http://www.whatsmyip.org/http_compression/ here].

When textual content is compressed using mod_gzip, it should maintain its [MIME-type](/source/Internet_media_type), according to their recommended media type:
* HTML: text/html
* [XHTML](/source/XHTML): application/xhtml+xml
* CSS: text/css
* [JavaScript](/source/JavaScript): application/x-javascript

One of the earliest Apache 1.3 versions introduced some internal function for [regular expression](/source/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.<ref>[http://schroepl.net/projekte/mod_gzip/versions.htm mod_gzip requires Apache 1.3+]</ref>

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](/source/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.<ref>[http://newestindustry.org/2006/10/03/compressing-web-output-using-mod_deflate-and-apache-20x-2/ Comparison of mod_deflate and mod_gzip]</ref> 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](/source/PHP) similar effect achievable for the output of PHP scripts with:
* the [http://php.net/manual/en/function.ob-gzhandler.php ob_gzhandler()] and the [http://php.net/manual/en/function.gzencode.php gzencode()] functions;
* zlib.output_compression option in the php.ini file.

[CherryPy](/source/CherryPy) offers the ''Gzip filter'',<ref>{{Cite web |url=http://www.cherrypy.org/wiki/GzipFilter |title=CherryPy offers the Gzip filter |access-date=2009-10-11 |archive-url=https://web.archive.org/web/20050212003622/http://www.cherrypy.org/wiki/GzipFilter |archive-date=2005-02-12 |url-status=dead }}</ref> which uses the [https://web.archive.org/web/20100225005805/http://www.python.org/doc/2.5.2/lib/module-zlib.html zlib module] of Python standard library.

==License==

The mod_gzip module licensed with [Apache License](/source/Apache_License).

==History==
Module level content compression for Apache started with mod_gzip, written by Kevin Kiley and Konstantin Balashow<ref>{{Cite web|url=http://www.webreference.com/interviews/petercranstone2.html|title=WebReference Featured Interview|last=Cranstone|first=Peter|date=2000-10-17|website=www.webreference.com|access-date=2017-07-02}}</ref> in autumn 2000, documented by Michael Schröpl,<ref>{{Cite web |url=http://www.linuxplanet.com/linuxplanet/tutorials/5461/2/ |title=mod_gzip written by Michael Schröpl |access-date=2009-10-11 |archive-date=2008-09-17 |archive-url=https://web.archive.org/web/20080917014155/http://www.linuxplanet.com/linuxplanet/tutorials/5461/2/ |url-status=dead }}</ref><ref>[http://schroepl.net/projekte/mod_gzip/ mod_gzip written in autumn 2000]</ref> published by [http://remotecommunications.com Remote Communications Inc.] (RCI).<ref>[http://schroepl.net/projekte/mod_gzip/ RCI had originally published mod_gzip]</ref> RCI was purchased by HyperSpace Communications, RCI released the code into the [public domain](/source/public_domain).<ref>[http://www.webreference.com/internet/software/servers/http/compression/2.html RCI released the code into the public domain]</ref>

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

==See also==
{{Portal|Free and open-source software}}
* [mod_deflate](/source/mod_deflate)
* [HTTP compression](/source/HTTP_compression)
* [Some general purpose Apache modules](/source/Mod_ssl)
* [Some programming language interfaces for Apache](/source/Mod_ssl)

==External links==
* [http://www.schroepl.net/projekte/mod_gzip/ Original homepage] of mod_gzip.
* Starting with version 1.3.19.2a mod_gzip has found a [https://sourceforge.net/projects/mod-gzip/ new home] on SourceForge.

==Notes==
{{Reflist}}

Category:Web server software
Category:Articles with underscores in the title
Category:Apache httpd modules

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Adapted from the Wikipedia article [Mod gzip](https://en.wikipedia.org/wiki/Mod_gzip) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Mod_gzip?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.