Core Web Vitals: What They Are and How to Improve Your Scores

In 2021, Google officially made page experience — measured through Core Web Vitals — a ranking factor. This meant that a slow, visually unstable website would rank lower than a fast, stable competitor with similar content quality. If you've heard about Core Web Vitals but aren't sure what they mean practically for your website, this guide explains it clearly.

What Are Core Web Vitals?

Core Web Vitals are three specific metrics Google uses to measure real-world user experience on your website:

Largest Contentful Paint (LCP): Measures loading performance — specifically, how long it takes for the largest visible content element (usually a hero image or main heading) to appear on screen. Target: under 2.5 seconds. Above 4 seconds = Poor.

Interaction to Next Paint (INP): Measures responsiveness — how quickly the page responds to user interactions (clicks, taps, key presses). Replaced First Input Delay (FID) in 2024. Target: under 200 milliseconds. Above 500ms = Poor.

Cumulative Layout Shift (CLS): Measures visual stability — how much the page layout shifts unexpectedly as it loads. Ever clicked a button and hit something else because an ad loaded and shifted everything? That's a high CLS. Target: under 0.1. Above 0.25 = Poor.

How to Check Your Core Web Vitals

The most reliable way is Google Search Console's Core Web Vitals report (uses real user data). You can also use:

• PageSpeed Insights (pagespeed.web.dev) — tests individual URLs
• Google Chrome DevTools (Lighthouse) — local testing
• GTmetrix — detailed waterfall analysis
• Web Vitals Chrome Extension — real-time measurement while browsing

Improving LCP (Largest Contentful Paint)

LCP is most commonly hurt by large, unoptimized images. Fix:

• Compress all images using tools like TinyPNG or Squoosh, or use WebP format
• Add explicit width and height attributes to images so browsers allocate space early
• Use lazy loading for below-fold images (but NOT for the largest above-fold image)
• Enable server-side caching and use a CDN to reduce server response time
• Remove render-blocking JavaScript and CSS

Improving INP (Interaction to Next Paint)

INP issues typically come from too much JavaScript executing when users interact with the page. Fix:

• Minimize and defer non-critical JavaScript
• Break long tasks into smaller chunks using async/await patterns
• Reduce the use of heavy JavaScript libraries where simpler code would work
• Remove unused plugins and extensions (especially on WordPress)

Improving CLS (Cumulative Layout Shift)

CLS is usually caused by images without dimensions, ads loading above content, or web fonts causing text to shift. Fix:

• Always set width and height attributes on images and video elements
• Reserve space for ads and embeds so they don't push content down when they load
• Use font-display: swap carefully for web fonts, or preload critical fonts
• Avoid inserting content above existing content after the page loads

Core Web Vitals improvement is ongoing work, not a one-time fix. As you update your website, add new plugins, or change your theme, scores can degrade. Build quarterly checks into your technical SEO routine.