PageSpeed mod_pagespeed is a module for Apache server which is just like a plugin, and since Apache is different from IIS, it cannot be installed on IIS servers.
As for what it does, it does multiple things:
In addition to minifying JS, it combines multiple external JS files into one JS file which causes less http requests or round trips so the page loads faster
Optimizes the cache for the files. Every http header has a cache information, or in other words, for how long should the browser keep the resource, mod_pagespeed optimizes this number
Uses the idea of URL fingerprinting for the new JS files. Basically when the mod_pagespeed optimizes and combines multiple JS files into one file, this temporary file is stored somewhere on the server, however, its filename is generated from the content of the JS files using checksum algorithms such as MD5. What this allows to do is that mod_pagespeed tells the browser to store the JS file for a long […] Continue Reading…