PageSpeed improves web page latency and bandwidth usage by changing the resources on that web page to implement web performance best practices. Each optimization is implemented as a custom filter in PageSpeed, which are executed when the HTTP server serves the website assets. Some filters simply alter the HTML content, and other filters change references to CSS, JavaScript, or images to point to more optimized versions.
PageSpeed implements custom optimization strategies for each type of asset referenced by the website, to make them smaller, reduce the loading time, and extend the cache lifetime of each asset. These optimizations include combining and minifying JavaScript and CSS files, inlining small resources, and others. PageSpeed also dynamically optimizes images by removing unused meta-data from each file, resizing the images to specified dimensions, and re-encoding images to be served in the most efficient format available to the user.
PageSpeed ships with a set of core filters designed to safely optimize the content of your site without affecting the look or behavior of your site. In addition, it provides a number of more advanced filters which can be turned on by the site owner to gain higher performance improvements.
PageSpeed can be deployed and customized for individual web sites, as well as being used by large hosting providers and CDNs to help their users improve performance of their sites, lower the latency of their pages, and decrease bandwidth usage.
Features
Automatic website and asset optimization
Latest web optimization techniques
40+ configurable optimization filters
Free, open-source, and frequently updated
Deployed by individual sites, hosting providers, CDNs
Install mod_pagespeed module for apache on Debian 7 server
Download .deb package using the following command
For 64-bit users
#wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-stable_current_amd64.deb
For 32-bit users
#wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-stable_current_i386.deb
If you see any errors run the following command
#apt-get -f install
Remove the downloaded package
#rm mod-pagespeed-*.deb
After installation you need to restart the apache server
#service apache2 restart
Configuring mod_pagespeed module
Depending on the Apache version you’re running, you’ll get a different version of the module installed and enabled. If you’re running Apache 2.2, mod_pagespeed.so will be installed; Apache 2.4 users will use mod_pagespeed_ap24.so.
Additionally, configuration files have been added to your Apache installation. The primary configuration file is pagespeed.conf.
This file is located in the following location
/etc/apache2/mods-available/
There are a few different ways mod_pagespeed can be configured. You can use the pagespeed.conf file described above to configure it for the whole server. Or, if you’d rather, you can put your configuration settings in the VirtualHost directive for an Apache virtual host/website. Finally, you have the option of specifying directives in a .htaccess file, such as what most sites do for mod_rewrite.
You can use whatever text editor you want to edit the configuration file.
To start editing the main configuration file, use the following command
#vi /etc/apache2/mods-available/pagespeed.conf
Basic Settings
In general, the settings in pagespeed.conf are pretty well documented inside the file. There is also a great list of filter examples available from http://www.modpagespeed.com. Here are a few common settings you might want to play with to optimize for your site’s performance.
Turn mod_pagespeed On/Off
First off, you can turn the module on or off with the ModPagespeed setting.
ModPagespeed on
or
ModPagespeed off
You can check the more configuration details from here