Core Web Vitals are Google's three headline measures of real-world page experience: how fast the main content loads, how quickly the page responds to input, and how much it shifts around while loading.
Core Web Vitals are Google's three headline measures of real-world page experience: how fast the main content loads, how quickly the page responds to input, and how much it shifts around while loading. Each maps to a specific metric, Largest Contentful Paint for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability.
The important word is real-world. These numbers come from the Chrome User Experience Report, anonymised data from actual Chrome visitors, not a single test on a fast connection. Google grades you at the 75th percentile, so a page passes a metric only when roughly three in four visits hit the 'good' threshold: 2.5 seconds or less for LCP, 200 milliseconds or less for INP, and a CLS of 0.1 or under. That is why a site can feel quick on your own machine and still fail. Your fibre connection and new laptop are not the median visitor on mobile data.
For a business owner the stakes are twofold. Core Web Vitals are a confirmed ranking signal inside Google's page experience system, one weighted alongside content relevance and quality rather than a lever that overrides them. The bigger prize is the visitor: a page that loads fast and does not jump around under your thumb keeps more people from bouncing before they have read a word. I treat them as part of technical SEO and build them into a site from the start rather than bolt them on later.
You can check them with Lighthouse or PageSpeed Insights, but be aware the two tell slightly different stories. Lighthouse runs a lab simulation on a throttled device, while the field data reflects your real Chrome users. When they disagree, chase the field data, because that is what Google actually scores you on.
Key points
- Three metrics: LCP (loading), INP (responsiveness) and CLS (visual stability). INP replaced First Input Delay in March 2024.
- Scored from real Chrome visitors via the Chrome User Experience Report, not a one-off lab test.
- Google grades at the 75th percentile, so roughly three in four visits must be 'good' to pass.
- The 'good' thresholds are LCP under 2.5s, INP under 200ms and CLS under 0.1.
- A confirmed ranking signal, but one of many, it will not outrank stronger, more relevant content.
- The real payoff is fewer people bouncing before the page has finished settling.
Frequently asked questions
Common questions about core web vitals.
Yes, but keep it in proportion. They sit inside Google's page experience signals and carry real ranking weight, but they will not outrank a page that is more relevant or higher quality. What they will not do is rescue thin content or push you above a genuinely more relevant competitor. Relevance and quality still do the heavy lifting. I fold Core Web Vitals into the wider SEO work rather than treating them as a standalone project, because on their own they rarely move a ranking on their own.
Because Google is not measuring your laptop. Core Web Vitals come from real Chrome visitors, and Google grades you at the 75th percentile, meaning most of your traffic needs to hit the threshold, not just your fast desktop on office wifi. A lot of your visitors are on mid-range phones and patchy mobile data. If that slower slice fails, the whole metric fails, even when the page feels instant to you. When you have field data, trust it over what you see locally; low-traffic pages sometimes will not clear Google's threshold for a reported field score, in which case the lab result from Lighthouse or PageSpeed Insights is what you have to go on.
In March 2024, Interaction to Next Paint (INP) became the responsiveness metric, replacing First Input Delay. It is a stricter, fairer test: FID only measured the delay before the browser started handling your first tap, while INP looks at the full round trip across all interactions, from the tap to the page visibly responding. If your site was already quick to react you likely have nothing to do. If it was borderline under FID, INP will expose sluggish JavaScript that FID quietly forgave.
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