Core Web Vitals

Core Web Vitals are Google's measurements of how a page feels to use: how quickly the main content appears, how quickly the page responds to the first interaction, and how much the layout shifts around while it loads. That last one is the metric behind the experience of reaching for a button as an advert pushes it aside.

They matter for two separate reasons. They are a ranking signal, so they affect how much traffic a site receives; and they are a reasonable proxy for whether the site is pleasant, so they affect what visitors do once they arrive.

The scores that count are collected from real visitors rather than from a test on a fast laptop. A site can pass every local audit and fail in the field, because the field includes mid-range phones on mobile networks.