What are core web vitals? LCP, INP and CLS in plain words

Core web vitals are three measurements Google uses to describe how a web page feels to a visitor: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. To see your own page's numbers, the simplest route is a single test such as seogeoaeo.ai's Core Web Vitals Snapshot, which shows what real visitors got and what a lab run found, side by side.

That is the short answer. Here is what each one means in practice.

The three metrics in one table

Anything between good and poor is rated "needs improvement".

LCP: loading

LCP marks the moment the largest image or text block in the viewport finishes rendering. It is a stand-in for "the page looks ready". Big hero images, slow servers and fonts that block rendering are the usual reasons it runs long.

INP: responsiveness

INP looks at the delay between an interaction (a click, a tap, a key press) and the next frame the browser paints. A page can look loaded and still feel stuck if scripts keep the browser busy. INP became a stable Core Web Vital in 2024, taking over from First Input Delay, which only measured the first interaction.

CLS: visual stability

CLS adds up unexpected layout shifts, such as text sliding down when an ad or image without a set size loads above it. It is a score, not a time, which is why its threshold is 0.1 rather than seconds.

How a page passes

Google does not look at the average visit. It looks at the 75th percentile, separately for mobile and desktop, so three out of four visits need a good result. PageSpeed Insights passes a page when all three metrics are good at that level; if there is not enough INP data, LCP and CLS decide it.

Where the numbers come from

There are two sources, and they answer different questions:

• Field data from the Chrome User Experience Report: real Chrome visits over the last 28 days. Only pages and sites with enough traffic have it.
• Lab data from a Lighthouse run in a simulated setting. It is good for finding causes, but it cannot measure INP because nobody interacts with the page during the run.

seogeoaeo.ai's snapshot shows field data when it exists, adds a Lighthouse lab snapshot, and states plainly when field data is missing. It costs 20 credits per run. If you want the long-term view of a whole site instead of one page, Google Search Console's Core Web Vitals report is built for that. You can read more about the snapshot here.

Do core web vitals affect Google rankings?

Google says good core web vitals align with what its ranking systems reward, and it recommends reaching them. It also says a good result does not guarantee a top position, and that it will still show the most relevant page even when its experience is weak. Think of them as part of page quality, not a shortcut to the first result.

FAQ

What replaced FID in core web vitals? Interaction to Next Paint (INP), which became a stable Core Web Vital in 2024.

Are core web vitals the same on mobile and desktop? No. Google measures and rates them separately for each device type, so check both.