Google's Core Web Vitals are three specific, measurable metrics that quantify real user experience — and they're a direct ranking factor. Here's what each one actually means and how to fix it.
Largest Contentful Paint (LCP)
LCP measures how long it takes for the largest visible element on the page — usually a hero image or main heading — to fully render. This is your user's perception of "is this page loading?" Google's target is under 2.5 seconds — see web.dev's official Core Web Vitals reference for the full methodology.
**Common causes of poor LCP:**
- Unoptimized, oversized images with no compression
- Render-blocking CSS and JavaScript loading before the main content
- Slow server response times (poor hosting or unoptimized database queries)
- Missing image preloading for the hero/above-the-fold image
**Fastest fixes:** compress and serve images in next-gen formats (AVIF/WebP), add fetchpriority="high" to your hero image, and eliminate render-blocking resources in the critical rendering path.
Interaction to Next Paint (INP)
INP measures how quickly your page responds when a user clicks, taps, or types — replacing the older First Input Delay (FID) metric in 2024. A page can load fast (good LCP) but still feel janky and unresponsive if INP is poor. Google's target is under 200 milliseconds.
**Common causes of poor INP:**
- Heavy JavaScript execution blocking the main thread
- Large third-party scripts (chat widgets, analytics, ad tags) competing for processing time
- Complex event handlers doing expensive work on every click
**Fastest fixes:** break up long JavaScript tasks, defer non-critical third-party scripts, and audit your JavaScript bundle size — most sites are shipping far more JavaScript than they actually need.
Cumulative Layout Shift (CLS)
CLS measures visual stability — how much content unexpectedly shifts around as the page loads. This is the frustrating experience of trying to tap a button and having an ad load in above it, shifting everything down at the last second. Google's target is under 0.1.
**Common causes of poor CLS:**
- Images and video without explicit width/height attributes, so the browser doesn't reserve space
- Ads, embeds, or dynamically-injected banners with no reserved space
- Web fonts loading late and causing a visible text reflow (FOIT/FOUT)
**Fastest fixes:** always set explicit width and height (or aspect-ratio) on images and embeds, reserve space for ad slots before they load, and use font-display: optional or preload critical fonts.
Why This Matters Beyond Rankings
Core Web Vitals aren't just an SEO checkbox — they correlate directly with bounce rate and conversion. Sites that improve their Core Web Vitals scores consistently see measurable increases in engagement and revenue, independent of any ranking benefit. Treat this as a user experience investment first, and an SEO win second. Run a free instant Core Web Vitals audit on your site, or see our full Technical SEO Audit Checklist.