How the page is loaded and measured
The tool requests the URL as your browser would, with your cookies and cache. Every resource the page fetches afterward, including scripts, stylesheets, images, fonts, and third-party embeds, is recorded with its byte count and type, and the totals are summed. The page is measured once per check, so lazy-loaded content that appears only after scrolling may not be fetched, and cached resources may be served without a full download.