As web developers, we all use web browser developer tools to monitor browser requests. The most commonly used ones are Firebug, Fiddler and Chrome Developer Tools.
Have you tried using these tools to determine which resources are served off the cache? You will be surprised to learn that only Chrome Developer Tool is able to correctly show the CDN resources coming from a cache.
Let’s see some results. I am accessing an ASP.NET site that makes use of some CSS and jQuery files served off the CDN. Feel free to choose a site of your choice like jQuery.com.
I observed that out of all the three browser tools, only Chrome clearly showed static resources coming from the cache. It was not easy to determine cache items using IE 9 and Firebug tool. See for yourself! I have refreshed the page a couple of times and also cleared the cache a couple of times.
Observe the misleading 304 result, when it should actually be coming from a cache. Eric Lawrence explains why does this happen.
Firebug too does not clearly show which static resources are fetched from the cache.
Using Chrome Developer Tool (Ctrl + Shift + I)
As you can see, Chrome clearly shows which static resources are fetched from the cache.