This is very likely how Google measures site speed for ranking, as well as anonymous submissions from the Google Toolbar. Google Analytics also lets you filter

This is very likely how Google measures site speed for ranking, as well as anonymous submissions from the Google Toolbar. Google Analytics also lets you filter this data by other metrics such as browser and geographic location. As for the W3C timing spec, it looks like Firefox is planning on implementing this too: https://bugzilla.mozilla.org/show_bug.cgi?id=570341 https://bugzilla.mozilla.org/show_bug.cgi?id=570341