Display file size of externally loaded resources for an HTML page

Question

In the article \"How we keep GitHub fast\", they describe a toolbar that GitHub staff members can use to see various performance metrics of each page load. Two of the items disp

Answer 1

I guess they've used a browser extension like speedtracer, which has access to the same metrics the network panel of your debugger shows you.

JavaScript has usually no access to external ressources, however it might be possible to load them via XHR to inspect them. Also, you might be able to get some of those information via the Navigation-Timing API (see html5rocks article).

And of course, they have a connection open to their servers to get those internal server metrics. It might as well be possible they get the information about served resources via that channel, and not from a javascript api.