Core Web Vitals: how to measure and improve LCP, INP and CLS
What each metric measures, how to check it with real data and the changes that usually have the most impact.
The three metrics
LCP measures how long the main element of the page takes to appear (usually a large image or text block). INP measures how quickly the page responds to user interactions. CLS measures how much content moves while the page loads.
Google recommends LCP of 2.5 seconds or less, INP of 200 milliseconds or less and CLS of 0.1 or less, assessed with field data at the 75th percentile.
Measure with real data
Lighthouse on your laptop is useful for debugging, but what matters for search is data from real users. Tools such as the Core Web Vitals report in Search Console or your platform's performance analytics show that information.
Measure before and after each change, and on the pages that receive the most traffic, not only on the home page.
The changes that usually matter most
For LCP: optimise and size the main image, preload it if it is above the fold, and avoid rendering the main content only after JavaScript has loaded.
For CLS: always reserve space for images, videos and ads. For INP: reduce the JavaScript that runs on interaction, split long tasks and avoid heavy work on every scroll or input event.