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mod_deflate

Created by brandon. Last edited by glenn, 247 days ago. Viewed 2,782 times. #13

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The Apache mod_deflate module compresses output on your server before sending it to the client. All modern browsers support this feature, and it is an easy way to stretch your bandwidth a little farther. Depending on the content on your site, you can see bandwidth savings of up to 25%

To enable, make sure that you have the Apache mod_deflate module installed (it is by default on most installations). Then simply put copy/paste these settings into your Apache config file

## Enable the module LoadModule deflate_module modules/mod_deflate.so

# Create the output 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

## Don't compress for IE5.0 BrowserMatch "MSIE 5.0" no-gzip

# Don't compress images, flash, PDFs, or JavaScript # You might want to add more extensions to this list such as ogg|mp3|mov|avi SetEnvIfNoCase Request_URI.(?:gif|jpe?g|png|swf|pdf)$ no-gzip dont-vary

# Make sure proxies don't deliver the wrong content Header append Vary User-Agent env=!dont-vary

## Sset up some stuff for mod_deflate stats DeflateFilterNote Input instream DeflateFilterNote Output outstream DeflateFilterNote Ratio ratio

LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate

## END mod_deflate configuration

Sometimes you want to deflate only text files. For that, comment out the SetEnvIfNoCase line and replace the "SetOutputFilter DEFLATE" line with the following:

AddOutputFilterByType DEFLATE text/css text/csv text/html text/plain application/xml application/xhtml+xml image/x-icon

Now, you can also add some extra logging to a virtual host to have the module save compression statistics about each request

CustomLog /var/logs/httpd/deflate.log deflate

Once you've made all of these changes to the Apache config, restart Apache to have them take effect.

Once you've been serving compressed files for a little while, you can use a script like the one at http://prefetch.net/code/deflate-stats.pl to analyze the deflate_log and tell you how much bandwidth you have saved.

You can also use this handy link to test your setup, and if your browser is sending the right Accept-Encoding:

http://www.whatsmyip.org/mod_gzip_test/

If your enabling mod_deflate because your site seems slow, and uses a lot of images or multimedia files, this link may be helpful:

http://developer.yahoo.com/performance/rules.html

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