Enable Gzip Compression On Apache HTTP Server

In this tutorial, we will discuss the steps required to enable Gzip compression of static resources served by the Apache HTTP Server. When the browser or HTTP client sends a request to web server, the web server either generate the response(HTML) or locate the resource i.e. image, JavaScript, CSS and try to compress where possible before replying back to the browser or HTTP client. This is where Gzip compression happens where the web server further compresses the resources before sending it to the requestor.

The deflate output filter available in the mod_deflate module does the heavy lifting job to compress and serve the static resources including HTML, images, JavaScript, CSS, etc.

Check Module

Though the module is enabled by default in Apache, we can always check whether it's available as shown below.

a2enmod deflate

On WAMP installation, it's disabled by default. It looks like the one shown in Fig 1 using System Tray. Click on the deflate_module option to enable it.

Fig 1

Also, check the apache configuration file to make sure that the module is enabled.

# Locate the file httpd.conf and make sure that it is enabled.



# Ebabled - All is well

LoadModule deflate_module modules/mod_deflate.so



# Disabled - Remove # and save the file to enable it

# LoadModule deflate_module modules/mod_deflate.so

Gzip Compression

The simplest form to enable Gzip compression is to add below-mentioned line to the .htaccess file.

# Enable Gzip compression for html, text, xml, css, and javascript

AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript

We can also update the virtual host as shown below. In the case where it's not possible to update the virtual host, we can always go with the .htaccess option.

<Directory "/site">

....



# Enable Gzip compression for html, text, xml, css, and javascript

AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript



....

</Directory>

The complete solution is as shown below. We can also configure a few more parameters to further enhance the compression by playing with the deflate_module options including DeflateCompressionLevel, DeflateMemLevel, and DeflateWindowSize.

<IfModule mod_deflate.c>

  # Compress HTML

  AddOutputFilterByType DEFLATE text/html



  # Compress Text

  AddOutputFilterByType DEFLATE text/plain



  # Compress CSS

  AddOutputFilterByType DEFLATE text/css



  # Compress JavaScript

  AddOutputFilterByType DEFLATE application/javascript

  AddOutputFilterByType DEFLATE text/javascript

  AddOutputFilterByType DEFLATE application/x-javascript



  # Compress Images

  AddOutputFilterByType DEFLATE image/svg+xml

  AddOutputFilterByType DEFLATE image/x-icon



  # Compress Fonts

  AddOutputFilterByType DEFLATE application/vnd.ms-fontobject

  AddOutputFilterByType DEFLATE application/x-font

  AddOutputFilterByType DEFLATE application/x-font-opentype

  AddOutputFilterByType DEFLATE application/x-font-otf

  AddOutputFilterByType DEFLATE application/x-font-truetype

  AddOutputFilterByType DEFLATE application/x-font-ttf

  AddOutputFilterByType DEFLATE font/opentype

  AddOutputFilterByType DEFLATE font/otf

  AddOutputFilterByType DEFLATE font/ttf



  # Compress XML

  AddOutputFilterByType DEFLATE application/rss+xml

  AddOutputFilterByType DEFLATE application/xhtml+xml

  AddOutputFilterByType DEFLATE application/xml

  AddOutputFilterByType DEFLATE text/xml



  # Old browser fixes

  BrowserMatch ^Mozilla/4 gzip-only-text/html

  BrowserMatch ^Mozilla/4\.0[678] no-gzip

  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

  Header append Vary User-Agent

</IfModule>

This is the easiest way to enable Gzip compression of websites hosted on Apache HTTP Server.