The mod_deflate module provides the DEFLATE output filter that allows output from your server to be compressed before being sent to the client over the network.
Sample Configurations
This is a simple sample configuration for the impatient.
Compress only a few types
AddOutputFilterByType DEFLATE
The following configuration, while resulting in more compressed content, is also much more complicated. Do not use this unless you fully understand all the configuration details.
Compress everything except images
# Insert filter
SetOutputFilter DEFLATE# Netscape 4.x has some problems…
BrowserMatch ^Mozilla/4 gzip-only-text/html# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won’t work. You can use the following
# workaround to get the desired effect:
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html# Don’t compress images
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png)$ no-gzip dont-vary# Make sure proxies don’t deliver the wrong content
Header append Vary User-Agent env=!dont-vary
Enabling Compression
Output Compression
Compression is implemented by the DEFLATE filter. The following directive will enable compression for documents in the container where it is placed:
SetOutputFilter DEFLATE
Some popular browsers cannot handle compression of all content so you may want to set the gzip-only-text/html note to 1 to only allow html files to be compressed (see below). If you set this to anything but 1 it will be ignored.
If you want to restrict the compression to particular MIME types in general, you may use the AddOutputFilterByType directive. Here is an example of enabling compression only for the html files of the Apache documentation:
AddOutputFilterByType DEFLATE text/html
For browsers that have problems even with compression of all file types, use the BrowserMatch directive to set the no-gzip note for that particular browser so that no compression will be performed. You may combine no-gzip with gzip-only-text/html to get the best results. In that case the former overrides the latter. Take a look at the following excerpt from the configuration example defined in the section above:
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
At first we probe for a User-Agent string that indicates a Netscape Navigator version of 4.x. These versions cannot handle compression of types other than text/html. The versions 4.06, 4.07 and 4.08 also have problems with decompressing html files. Thus, we completely turn off the deflate filter for them.
The third BrowserMatch directive fixes the guessed identity of the user agent, because the Microsoft Internet Explorer identifies itself also as “Mozilla/4″ but is actually able to handle requested compression. Therefore we match against the additional string “MSIE” (\b means “word boundary”) in the User-Agent Header and turn off the restrictions defined before.
Note
The DEFLATE filter is always inserted after RESOURCE filters like PHP or SSI. It never touches internal subrequests.
source : apache.org
