Core Web Vitals are standardized metrics developed by Google to quantify key aspects of user experience. They became official Google ranking factors in June 2021, meaning pages with poor CWV scores rank lower than otherwise comparable pages that pass.
LCP — Largest Contentful Paint
LCP measures how long it takes for the largest visible content element (image, video, or text block) to render. Target: under 2.5 seconds. Common causes of slow LCP: large unoptimized images, slow server response times, render-blocking JavaScript, and client-side rendering.
INP — Interaction to Next Paint
INP (which replaced FID in March 2024) measures how quickly a page responds to user interactions — clicks, taps, keyboard inputs. Target: under 200ms. A slow INP makes pages feel sluggish and frustrating. Common causes: heavy JavaScript execution, large DOM size.
CLS — Cumulative Layout Shift
CLS measures visual stability — how much content shifts unexpectedly as the page loads. Target: under 0.1. A high CLS is when you go to click a button and it moves at the last second. Caused by: images/ads without dimensions, late-loading fonts, dynamically injected content.
How CWV Affects Rankings
Pages that "pass" CWV (meeting all three thresholds) rank higher than pages that fail when content quality is otherwise similar. The advantage is most pronounced for competitive queries where many pages have similar content quality.
Measuring Core Web Vitals
Use Google PageSpeed Insights for lab data on any URL. Google Search Console shows field data (real user measurements) aggregated across your site. Chrome UX Report provides detailed breakdowns by device type and connection speed.
Improving Core Web Vitals
LCP: optimize images (WebP, proper sizing, lazy loading), improve server response time (TTFB), eliminate render-blocking resources. INP: reduce JavaScript execution time, minimize main thread work. CLS: always specify width and height for images and videos, avoid inserting content above existing content.