Medium impact · weight 5 · worth up to 3.1 points of the total score
How long the server took to start answering, measured on our own request. A slow first byte delays everything downstream no matter how well the front end is built.
Cache the response, remove slow database queries from the request path, or move the origin closer to visitors with a CDN.
Check a page for this, and the other 41 checks at once
Response carries cache headers
Without a usable Cache-Control header, browsers and CDNs re-fetch the page on every visit, so returning visitors pay the full load cost again for content that did not change.
HTML document weight
This is the HTML document alone, before images and scripts. A multi-megabyte document usually means the whole page was rendered server-side into one response, and every visitor pays for it on every load.
Lighthouse performance score
Google's own composite of loading, interactivity, and visual stability, measured on a simulated mid-range phone. This is the number PageSpeed Insights puts at the top of its report.
Largest Contentful Paint
LCP is the moment the biggest element in the viewport finishes rendering, which is when a visitor feels the page has arrived. Google's threshold for good is 2.5 seconds.
