Since no one mentioned it, I just wanted to make sure this thread is aware of the Network Information API [1], which provides navigator.connection.bandwidth
It's been recently implemented (to some degree) in both Mozilla [2] and Webkit [3]. [1] http://dvcs.w3.org/hg/dap/raw-file/tip/network-api/index.html [2] https://bugzilla.mozilla.org/show_bug.cgi?id=677166#c42 [3] http://trac.webkit.org/changeset/112815