Core Web Vitals Explained: What They Are and How to Improve Them

The three metrics

Core Web Vitals are Google’s measures of real-world page experience. They are based on data from real visits, so they reflect what users actually feel.

• Largest Contentful Paint (LCP): how quickly the main content appears. A good score is 2.5 seconds or less.
• Interaction to Next Paint (INP): how quickly the page responds to taps and clicks. A good score is 200 milliseconds or less.
• Cumulative Layout Shift (CLS): how much the layout jumps while loading. A good score is 0.1 or less.

Why they matter

Page experience is one of many signals in search ranking, and it also affects behaviour: slow or jumpy pages lose visitors before they act. Improving vitals tends to help both SEO and conversion.

Improving LCP

Most LCP problems come from large hero images, slow servers and render-blocking resources.

• Compress and correctly size the main image, and serve modern formats
• Preload the hero image and avoid lazy-loading it
• Improve server response with caching and a CDN
• Remove or defer render-blocking CSS and JavaScript

Improving INP

Slow interactions usually mean too much JavaScript running on the main thread.

• Remove unused scripts and third-party tags
• Split large bundles and defer non-critical code
• Avoid long tasks during user interaction

Improving CLS

Layout shifts come from elements that change size after they load.

• Set width and height on images and embeds
• Reserve space for ads, banners and late-loading content
• Load web fonts in a way that avoids reflow

Measure with field data first

Use Search Console’s Core Web Vitals report and PageSpeed Insights to see real-user data, then use Lighthouse in the lab to find causes.