Core Web Vitals are three measurements of real-user experience: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness and Cumulative Layout Shift (CLS) for visual stability. A page is rated good when, at the 75th percentile of visits, LCP is 2.5 seconds or less, INP is 200 milliseconds or less and CLS is 0.1 or less.
The three metrics
| Metric | What it measures | Good | Poor |
|---|---|---|---|
| LCP: Largest Contentful Paint | How long until the main content (usually the hero image or headline) appears | ≤ 2.5 s | > 4 s |
| INP: Interaction to Next Paint | How quickly the page responds visually after taps, clicks and key presses | ≤ 200 ms | > 500 ms |
| CLS: Cumulative Layout Shift | How much content unexpectedly jumps around while loading | ≤ 0.1 | > 0.25 |
INP replaced First Input Delay (FID) as a Core Web Vital in March 2024, because it reflects responsiveness across the whole visit rather than only the first interaction.
Field data vs lab data
Google assesses Core Web Vitals using field data: measurements from real Chrome users, collected in the Chrome UX Report, and looks at the 75th percentile. Tools like Lighthouse produce lab data: a simulated load on one device. Lab data is great for debugging; field data is what counts for your search appearance. PageSpeed Insights and Search Console show both.
Fixes that matter most on marketing sites
Improving LCP
- Serve hero images in modern formats (WebP or AVIF), at the right size, and don't lazy-load the hero.
- Render pages on the server or as static HTML instead of building them in the browser.
- Use a CDN and keep server response times low.
- Preload the main web font and keep the number of font files small.
Improving INP
- Ship less JavaScript: remove unused libraries, tag-manager bloat and heavy widgets.
- Break up long tasks so the main thread can respond to input.
- Load chat widgets, analytics and embeds after the page is interactive.
Improving CLS
- Always set width and height (or an aspect ratio) on images and videos.
- Reserve space for banners, embeds and ads before they load.
- Use
font-displayand size-matched fallback fonts to avoid text reflow.
Do Core Web Vitals affect rankings?
They are part of Google's page experience signals, but relevance and content quality matter far more. Treat good vitals as a tie-breaker for search, and as a direct win for conversion, because faster, steadier pages simply sell better.
Performance is built into every custom website we ship, including immersive scrollytelling pages.