Core Web Vitals explained: what to measure and how to fix it

Core Web Vitals are Google's way of measuring real-world page experience. They are a small ranking signal, but more importantly they track things users feel: how fast the page appears, how quickly it reacts and whether things jump around.

The three metrics

• Largest Contentful Paint (LCP): how long the biggest visible element takes to render. Aim for 2.5 seconds or less.
• Interaction to Next Paint (INP): how quickly the page responds to taps and clicks. Aim for 200 milliseconds or less.
• Cumulative Layout Shift (CLS): how much content moves unexpectedly. Aim for 0.1 or less.

Fixing LCP

• Serve the hero image in a modern format at the right size and prioritise its loading.
• Render above-the-fold content on the server.
• Use a CDN and cache static assets.

Fixing INP

• Ship less JavaScript and split large bundles.
• Avoid long tasks on the main thread, especially from third-party scripts.
• Keep event handlers light.

Fixing CLS

• Always set width and height (or aspect ratio) on images, videos and embeds.
• Reserve space for ads, banners and cookie notices.
• Use font-display settings and preload fonts to avoid text jumping.

How to measure

Use field data from Search Console and PageSpeed Insights, not only lab scores. Field data shows what real visitors experience. For a full launch checklist, see our Next.js SEO checklist.