What are Core Web Vitals? (CWV)

Core Web Vitals are Google's metrics measuring page loading, interactivity, and visual stability. Learn how CWV affects SEO and user experience.

Google's three standardized metrics that measure how fast pages load, how quickly they become interactive, and how stable the visual layout remains.

Core Web Vitals are a specific set of user experience measurements that Google uses as ranking signals. The three metrics - Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS) - quantify what users actually experience when visiting your pages. Passing thresholds on all three earns you a 'good' page experience score.

Deep Dive

Core Web Vitals represent Google's attempt to standardize how we measure user experience. Rather than relying on vague notions of 'fast' or 'responsive,' these metrics provide concrete thresholds that websites either pass or fail. The three metrics each target a different aspect of experience. LCP (Largest Contentful Paint) measures loading performance: how long until the main content is visible. The threshold is 2.5 seconds. INP (Interaction to Next Paint), which replaced FID in March 2024, measures responsiveness: how long after a click or tap before the page visually responds. The threshold is 200 milliseconds. CLS (Cumulative Layout Shift) measures visual stability: how much the page layout jumps around as it loads. The threshold is 0.1. Google collects this data from real Chrome users through the Chrome User Experience Report (CrUX). This means your scores reflect actual user experiences, not lab conditions. A page might score perfectly in Lighthouse testing but fail in the field because real users have slower devices or spotty connections. The ranking impact of Core Web Vitals is modest but real. Google has been clear that content relevance matters more, but when two pages are roughly equal in quality, CWV can be the tiebreaker. More practically, poor CWV often correlates with higher bounce rates and lower conversion rates, making the business case clearer than the SEO case. Fixing CWV issues typically requires collaboration between marketing and development teams. LCP problems usually stem from slow servers, unoptimized images, or render-blocking resources. INP issues often trace back to heavy JavaScript execution. CLS problems are frequently caused by images without dimensions, ads that inject late, or web fonts that swap. For most sites, the 80/20 approach works: fix your worst-performing pages first, particularly high-traffic landing pages. Tools like PageSpeed Insights and Google Search Console's Core Web Vitals report identify exactly which URLs need attention and what's causing the problems.

Why It Matters

Core Web Vitals matter because they quantify what users feel. A page that takes 5 seconds to load or shifts around as users try to click isn't just annoying - it drives people away. Studies consistently show that conversion rates drop significantly as page load times increase. For marketers, CWV provides a common language to communicate with developers. Instead of saying 'the page feels slow,' you can point to specific metrics with specific thresholds. This makes prioritization and progress tracking concrete. The SEO benefit is real but secondary: the primary value is keeping users engaged long enough to convert.

Key Takeaways

Three metrics: loading, interactivity, visual stability: LCP measures when main content appears, INP measures response to interactions, and CLS measures layout jumps. Each has a specific pass/fail threshold based on real user data.

Real user data, not lab scores, determines rankings: Google uses Chrome User Experience Report data from actual visitors. Your Lighthouse score might be perfect while field data fails because real users have diverse devices and connections.

Tiebreaker signal, not a dominant ranking factor: Content relevance still matters more. But among comparable pages, passing Core Web Vitals can provide an edge, and the UX benefits affect conversions directly.

INP replaced FID in March 2024: First Input Delay only measured the first interaction. Interaction to Next Paint captures responsiveness throughout the entire session, giving a more complete picture of page interactivity.