Load Time

Load time is the interval from the start of a page request until every resource on the page has finished loading, which is the moment of the browser's load event.

The interval starts when the browser begins navigation and ends at the load event, so it contains redirects, DNS lookup, connection setup, server wait, HTML parsing and the download of every image, script, stylesheet and iframe. Because it waits for the last byte of the last file, it says little about when the page became usable: a page can be readable in one second and still report six seconds because of a tracking script or an image below the fold. That gap is why Google's official criteria moved away from this metric towards measurements tied to what the visitor can see and do. In single-page apps the load event fires only once, so later in-app navigations produce no load time at all.