knowledgebase/linux/webserver/apache/mod_deflate 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 {code} ## 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|js|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 {code} Sometimes you want to deflate only text files. For that, comment out the SetEnvIfNoCase line and replace the "SetOutputFilter DEFLATE" line with the following: {code} AddOutputFilterByType DEFLATE text/css text/csv text/html text/plain application/xml application/xhtml+xml image/x-icon {code} Now, you can also add some extra logging to a virtual host to have the module save compression statistics about each request {code} CustomLog /\var/logs/httpd/deflate.log deflate {code} 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 2007-10-29 01:44:56.0 2007-02-08 19:33:14.0