An introduction to gzip / mod_deflate

What is mod_deflate?

Mod_deflate is an apache module that can be used to compress data using gzip compression before sending it to the user. For bandwidth intensive websites, using this feature can offer a benefit, as the server is compressing data before sending it you will be using less bandwidth. The major drawback to using mod_deflate however is that the server may need to use more resources to compress each file and this in turn can cause performance issues on older servers. As our shared accounts included unlimited bandwidth, using mod_deflate to reduce bandwidth usage is not usually a concern for shared users.

It's important to understand that gzip compression does not reduce resource usage on a server, nor is it guaranteed to reduce page load times for your website. To reduce possible resource usage and reduce page load time, a better solution is a caching option for your site. If your site is created with a Content Management System such as WordPress, Joomla, Drupal, etc.; there are modules or settings for each of those that will enable caching for your site. For example, the WP Super Cache Plugin will help you optimize your WordPress site. In Joomla, caching is a built-in module which you can enable in your Joomla administration panel.

Please note: Due to the performance issues that can be caused by mod_deflate, it should not be used on older shared servers. If you do not see the option for Optimize Website in your cPanel, you are on an older server that does not support gzip compression (mod_deflate).

How do I install mod_deflate?

The mod_deflate apache module is already installed on our servers.

How do I use mod_defalte?

To use mod_deflate, you have two options:

• Use the Website Optimization option in cPanel.
• Add a few lines to your .htaccess file.

Enabling mod_deflate (gzip compression) in cPanel

Under Software/Services in your cPanel click on the Website Optimization icon.

Select Compress all content or specific MIME types. To limit which types of content are compressed, choose Compress the specified MIME types and input the particular MIME types you want to compress.

If you specify particular MIME types, it is best not to add image, video, audio, PDF or other types of binary files. These file formats are already compressed, so it is not necessary to compress these further.

Once you have chosen your settings, click Update Settings to save your changes and enable gzip compression on your account.

To turn off gzip compression, select Disabled on the Website Optimization page and click Update Settings.

Enabling mod_deflate (gzip compression) in .htaccess

Edit your .htaccess file and add the following code:

<IfModule mod_deflate.c>
AddOutputFilterByType DEFLATE text/text text/html text/plain text/xml text/css application/x-javascript application/javascript
</IfModule>

How can I test if mod_deflate is working?

There are several sites online that you can use to help test whether mod_deflate is working for your site or not. One site we found rather easy to use is:

http://www.whatsmyip.org/http-compression-test/

All you need to do is enter a URL and click the "Test" button. Below we have showed before and after screenshots that show when mod_deflate is enabled, and when it is not.