It all sounds too easy. If you are running an Apache server, then all you have to do to make your web site run faster is install a new mod.

Google is of  the opinion that a faster web is a good thing. Specifically it is good for Google because more speed means more data and more data means more profit. Nothing wrong with this point of view, but it is nice to know why companies like Google are doing things to help you and not asking for a direct reward.

The mod_pagespeed software was introduced in 2010 as a way of speeding up the delivery of pages by the Apache server. It claimed a 2x improvement or better and it is particularly effective with CMS generated pages. After two years of being in beta the Google team are happy enough with it to give it a first release status - so any bugs you find now are real bugs.

Addiing mod_pagespeed is just a matter of installing a standard Apache module and this is easy and needs no special support from an ISP - although you will need admin rights. Some ISPs are offering the module as a standard install. A set of standard actions or filters are active on install but there are some more advanced options you can turn on and tune the system.

The speed improvements are achieved by managing resources better. It is the sort of thing that you would do if you had the time and never made a mistake. For example is rescales and recompresses images, combines CSS files and minifies CSS and JavaScript.

Is there a cost to this improvement?

Isn't there always. In this case there is an additional load on the CPU doing all that extra work and, of course, the biggest speedups involve the largest amount of work. Some users report a x3 increase in CPU loading for the x2 speed increase. So your pages may be served faster, but the number of users your server can support may be reduced.

You can see Google view of mod_pagespeed in the video below: