Core Web Vitals: what they measure and how to improve them
Core Web Vitals are metrics for loading performance, responsiveness and visual stability. Google uses them as part of its page experience signals, but they are not a shortcut to higher rankings. Relevant content and the wider search system still matter.
The three current metrics
Largest Contentful Paint (LCP) measures when the largest visible content element finishes rendering. A good result is 2.5 seconds or less.
Interaction to Next Paint (INP) measures how quickly a page provides visual feedback after user interactions. A good result is 200 milliseconds or less.
Cumulative Layout Shift (CLS) measures unexpected movement in the page layout. A good result is 0.1 or less.
For each metric, the recommended assessment uses the 75th percentile of real visits, split by mobile and desktop where enough data is available.
Field data and lab tests
Field data comes from real users and reflects their devices, networks and interactions. It is available through tools such as the Chrome User Experience Report, PageSpeed Insights and Search Console when a page or origin has enough traffic.
Lab tools such as Lighthouse are useful for debugging in a controlled environment. They can help reproduce problems, but a single lab score does not replace field data.
Improving LCP
Start with the element reported as the LCP candidate. Common improvements include reducing server response time, prioritising the main image, using appropriate image dimensions and formats, and avoiding render-blocking work above the fold.
Improving INP
Look for long JavaScript tasks and event handlers that do too much work. Reduce unnecessary client-side code, split expensive work and provide immediate visual feedback where longer processing is unavoidable.
Improving CLS
Reserve space for images, embeds and dynamic components. Avoid inserting content above what the visitor is already reading. Font loading should also be configured to limit unexpected changes in text dimensions.
Measure again after each meaningful change. The useful outcome is not a perfect badge, but a site that loads, responds and stays stable for the people using it.