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Simple Apache Performance Improvements

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Simple Apache Performance Improvements

Here is a small collection of simple performance improvements using Apache.

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This post collects together a number of simple performance improvements using apache; it demonstrates using mod_expires, mod_deflate, mod_cache, and mod_headers. 

.htaccess or httpd.conf

httpd.conf provides the core apache configuration, while .htaccess provides a directory specific configuration. The preference is to use httpd.conf where possible, because using htaccess results in a search for htaccess on every sub-directory of a request, for each request. Depending on your hosting this decision may be out of your hands.


mod_deflate tells apache to compress responses from your application server. The options are:

  • AddOutputFilterByType - To use this option you must enable mod_filter -
    LoadModule filter_module modules/mod_filter.so
  • AddOutputFilterByType DEFLATE text/html text/xml text/css text/plain


<filesMatch "\.(js|html)$">
  SetOutputFilter DEFLATE

If you use AddOutputFilterByType then you need to make sure you have the mime-types defined.

Other directives:

  • DeflateCompressionLevel - 1 to 9 - the higher the value, the greater compression but the cost is higher CPU
  • You can also enable mod_deflate logging to see the compression ratios on your files.

Putting it together:

LoadModule filter_module modules/mod_filter.so
LoadModule deflate_module modules/mod_deflate.so

<IfModule mod_deflate.c>
    # List of mime types -
    AddOutputFilterByType DEFLATE text/html text/xml text/css text/plain
    AddOutputFilterByType DEFLATE image/svg+xml application/xhtml+xml application/xml
    AddOutputFilterByType DEFLATE application/rdf+xml application/rss+xml application/atom+xml
    AddOutputFilterByType DEFLATE text/javascript application/javascript application/x-javascript application/json
    AddOutputFilterByType DEFLATE application/x-font-ttf application/x-font-otf
    AddOutputFilterByType DEFLATE font/truetype font/opentype

    # May tune as a result of load testing
    DeflateCompressionLevel 9

    # Browser Specific rules -
    BrowserMatch ^Mozilla/4 gzip-only-text/html
    BrowserMatch ^Mozilla/4\.0[678] no-gzip
    BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
    BrowserMatch \bOpera !no-gzip


This module sets the Expires HTTP header and max-age of Cache-Control in HTTP header.

The format is:

  • ExpiresByType mime-type "access plus y years m months d days h hours"

A typical configuration would be:

LoadModule expires_module modules/mod_expires.so

<IfModule mod_expires.c>
    ExpiresActive on
    ExpiresDefault "access plus 30 days"

    ExpiresByType image/jpg "access plus 30 days"
    ExpiresByType image/png "access plus 30 days"
    ExpiresByType image/gif "access plus 30 days"
    ExpiresByType image/jpeg "access plus 30 days"

    ExpiresByType text/css "access plus 1 days"

    ExpiresByType image/x-icon "access plus 30 days"

    ExpiresByType application/pdf "access plus 30 days"
    ExpiresByType audio/x-wav "access plus 30 days"
    ExpiresByType audio/mpeg "access plus 30 days"
    ExpiresByType video/mpeg "access plus 30 days"
    ExpiresByType video/mp4 "access plus 30 days"
    ExpiresByType video/quicktime "access plus 30 days"
    ExpiresByType video/x-ms-wmv "access plus 30 days"
    ExpiresByType application/x-shockwave-flash "access 30 days"

    ExpiresByType text/javascript "access plus 30 days"
    ExpiresByType application/x-javascript "access plus 30 days"
    ExpiresByType application/javascript "access plus 30 days"


This plugin customises HTTP request and response headers, and we can use it to set the max-age on Cache-Control -

LoadModule headers_module modules/mod_headers.so

<ifModule mod_headers.c>
    <filesMatch "\.(ico|jpe?g|png|gif|swf)$">
        Header set Cache-Control "max-age=2592000, public"
    <filesMatch "\.(css)$">
        Header set Cache-Control "max-age=604800, public"
    <filesMatch "\.(js)$">
        Header set Cache-Control "max-age=216000, private"
    <filesMatch "\.(x?html?|php)$">
        Header set Cache-Control "max-age=600, private, must-revalidate"
<ifModule mod_headers.c>
    Header unset Last-Modified


An ETag is a unique ID for a resource and is configured per server. The problem is that in some clustered environments you can end up caching the same resource due to them having different ETags. A decision on disabling ETag's should be made on an environment basis, as disabling them forces the browser to rely on Cache-Control and Expires headers.

The syntax to disable is:

LoadModule headers_module modules/mod_headers.so

FileETag None
<ifModule mod_headers.c>
    Header unset ETag

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