Core Web Vitals in 2026: The Three Metrics Google Measures

Core Web Vitals are the three user experience metrics Google uses to measure how a real page feels to a real visitor. They are part of how Google judges page experience, and they map closely to the things people actually notice: how fast the main content appears, how quickly the page reacts when you tap, and whether the layout jumps around while it loads.

This guide explains each metric, the threshold that counts as good, and the practical fixes that move the numbers. When you want to check the rest of your technical SEO, the SEO Audit Checklist → walks through the full picture.

The three metrics at a glance

One detail matters for all three: they are measured at the 75th percentile of real user visits. That means you need three quarters of your visits to hit the good threshold, not just your fast test on a fast laptop. Field data from real devices is what counts, and it always looks worse than a clean lab run.

Largest Contentful Paint

LCP marks the moment the largest visible element finishes rendering, usually a hero image, a video poster, or a big block of headline text. A good LCP is under 2.5 seconds. Above 4 seconds is poor.

The usual culprits are slow servers, render blocking resources, and oversized images. The fixes are direct:

<link rel="preload" as="image" href="/hero.webp">
<img src="/hero.webp" width="1200" height="600" fetchpriority="high" alt="...">

Serve the hero image in a modern format, give it explicit dimensions, preload it, and mark it high priority. On the server side, fast response times and a CDN close to your users do more for LCP than almost anything else.

Interaction to Next Paint

INP replaced First Input Delay as a Core Web Vital in March 2024. The difference matters. FID only measured the delay before the browser started processing the first interaction. INP measures the full response, from tap to the next frame painted, across all interactions on the page, and reports a value near the worst one. A good INP is under 200 milliseconds.

Because INP is about responsiveness, the fixes target the main thread. Break long JavaScript tasks into smaller chunks, defer work that does not need to happen immediately, and avoid heavy layout recalculations on every click.

// Yield to the browser so input stays responsive
async function handleClick() {
  doUrgentWork();
  await new Promise(r => setTimeout(r, 0));
  doDeferrableWork();
}

Cumulative Layout Shift

CLS measures how much visible content jumps around without the user causing it. You have felt this: you go to tap a button, an ad loads above it, and the whole page lurches. A good CLS is under 0.1.

Layout shift comes from elements that load without reserved space. The fixes are simple and reliable:

Always set width and height on images and video so the browser reserves the box before the file arrives. Reserve space for ads and embeds with a fixed minimum height container. Preload fonts and use font-display: optional or swap carefully so text does not reflow when the web font loads.

Lab data versus field data

There are two ways to measure these metrics and they tell different stories. Lab tools run a single test in a controlled environment, which is great for debugging. Field data comes from real visits over the prior 28 days and is what Google actually uses. Treat lab runs as a fast feedback loop while you work, and trust field data as the verdict.

A realistic workflow

Start by pulling your field data to see which of the three metrics is failing at the 75th percentile. Fix the worst one first, since one failing metric can drag the whole page experience score. Re-measure after each change rather than batching ten fixes at once, so you know which one moved the needle. Remember the 28 day window means field numbers update slowly, so use lab tools for quick confirmation in between.

Related reading

Page speed is one piece of a wider picture, so pair this with the SEO audit checklist and a clean meta tags setup.

Bottom line

Three metrics, three thresholds: LCP under 2.5 seconds, INP under 200 milliseconds, CLS under 0.1, all judged at the 75th percentile of real users. Most sites fail one of them, and the fix is usually unglamorous: size your images, trim your JavaScript, reserve space before things load. Pair this with the SEO Audit Checklist → and tidy your head with the Meta Tag Generator → for a page that ranks and feels fast.