What are Core Web Vitals, and do they actually affect rankings?
A small set of metrics measuring loading, interactivity and visual stability as experienced by real users — and the honest answer on rankings is that they are a genuine but weak signal, far less influential than relevance, and considerably more influential on conversion than on position.
The three current metrics:
Largest Contentful Paint (LCP) — how long until the main content appears. Measures perceived loading speed rather than technical load completion.
Interaction to Next Paint (INP) — how quickly the page responds to user interactions across the whole visit. It replaced First Input Delay, which only measured the first interaction and was too easy to pass.
Cumulative Layout Shift (CLS) — how much content moves unexpectedly while loading. This is the one users feel most acutely, as the button that moves as you tap it.
Field data versus lab data, which is the distinction that matters. Field data comes from real users on real devices and networks, and is what search engines use. Lab data from a testing tool is reproducible and diagnostic and is not what you are assessed on — which is why a perfect lab score can accompany failing field metrics.
What actually causes each to fail:
LCP — slow server response, render-blocking resources, unoptimised images, and lazy-loading the hero image, which is a common own goal.
INP — heavy JavaScript occupying the main thread, especially third-party tags.
CLS — images and ads without reserved dimensions, late-loading fonts, and content injected above existing content.
The honest position on ranking impact. Page experience is a tiebreaker among comparable results, not a substitute for relevance — better content on a slower page generally still wins. Search representatives have consistently described it in these terms.
Why to care anyway, which is the stronger argument: speed and stability measurably affect bounce, conversion and revenue, and the commercial case does not depend on rankings at all.
Third-party scripts are usually the culprit, and auditing tag managers is the highest-value action available.