Being rather new to real high speed Internet I sometimes play with the Speedtest. It always seems to default to a Comcast server in Atlanta GA, giving me ping times usually around 60-90 msec and download/upload speeds on the order of 30/20 Mbps. Having once accidentally (I've no idea how it happened) landed on a server in San Jose CA (much closer, I am only a couple of hundred miles away) I noticed strikingly faster speeds (ping <20 msec) and wonder w hat is going on. Supposedly the program is searching for the "best" server but in fact if I don't fiddle with it it always lands on the Comcast one in Atlanta - it seems to think I am located in the East. I am an Easterner by birth (born in Boston!) but have lived in the West for a good many years now (I even wear Wranglers and Justin boots and what back East would be called a funny hat, though those things are mostly dictated by the nature of my work).
Note I am not complaining about my Internet service, which seems to be more than adequate (for watching live sports for example) nor about Speedtest which I understand to be only an approximate tool anyway. I also recognize that the "measured" speeds can vary quite a bit according to time of day and goodness knows what and even from minute to minute (right now we are having a terrific dust storm with howling wind, though it doesn't seem to be disturbing my Internet reception at all)
I am just curious about how the Speedtest actually works, and how it picks its sites, etc.
BTW when I first encountered that site it was pushing some dubious software ... but installing the MVPS "hosts" file seems to have eliminated that.