Core Web Vitals: what they are and why Google cares

Core Web Vitals are three specific numbers Google uses to measure how a page feels to a real person using it. They are part of Google's search ranking algorithm — not the biggest part, but a part that is measurable, fixable, and increasingly weighted.

The three metrics

Largest Contentful Paint (LCP) measures how long it takes for the main content of the page to appear. When you open a page and stare at a blank screen, the LCP is the moment the thing you came to see finally loads. Google considers an LCP under 2.5 seconds to be good. Above 4 seconds is poor. On a mid-range phone over a cellular connection, most small business sites are in the poor range.

Interaction to Next Paint (INP) measures how fast the page responds when you tap something. If you tap a menu button and the menu takes half a second to open, that is a bad INP. Under 200 milliseconds is good; above 500 is poor. INP replaced an older metric (First Input Delay) in March 2024 because the old one only measured the first interaction, and a page can be fast on the first tap and sluggish on the tenth.

Cumulative Layout Shift (CLS) measures how much the page jumps around while it loads. You have experienced this: you are about to tap a link, an image loads above it, and the link moves down. A CLS under 0.1 is good; above 0.25 is poor. It is the most common cause of the feeling that a site is cheap, even when you cannot name why.

Why Google uses these

Google's business depends on people finding search results useful. If the first result loads slowly, jumps around, and does not respond to taps, the searcher blames Google, not the site. Core Web Vitals are Google's way of making sure the sites it ranks highly are not just relevant but usable. The metrics are measured from real Chrome users who have opted in to share performance data, which means they reflect actual experience, not a synthetic test.

A fast LCP does not mean the page is useful. A good INP does not mean the content answers the question. But a page that fails all three is a page that drives visitors away before they can read a word, and Google knows it.

How a static site scores on Core Web Vitals

The sites I build are static — the pages are pre-built and served as-is, with no database to query and no plugin stack to load. This is the single biggest advantage of a static site for Core Web Vitals: the server response time is near zero because there is no server-side work to do. The page is already built.

The result is an LCP that is typically under a second, an INP that is effectively zero (there is no JavaScript blocking the main thread), and a CLS of zero (every image has reserved dimensions, so nothing shifts). This site scores 100 on Lighthouse Performance, which is the same tool Google uses to measure Core Web Vitals in the lab.

What it means for your site

If your site is built on a heavy builder platform with a lot of plugins, there is a good chance it has poor Core Web Vitals scores, and that is holding back your search ranking even if your content is good. The free audit will show you exactly where your site stands on all three metrics.