What Are Core Web Vitals?
Core Web Vitals are Google’s set of user-focused metrics that measure the quality of page experience. These three metrics assess how quickly a page loads, how responsive it is to user interaction, and how stable the content is as it loads.
The three Core Web Vitals are:
- Largest Contentful Paint (LCP): Measures loading speed.
- Interaction to Next Paint (INP): Measures responsiveness.
- Cumulative Layout Shift (CLS): Measures visual stability.
Google considers these signals important for ranking because they directly impact user experience.
Why Core Web Vitals Matter for SEO
Google officially integrated Core Web Vitals into its ranking algorithm as part of the Page Experience update. While they aren’t the most powerful ranking signals alone, they can give your site a competitive edge—especially when competing pages have similar content relevance.
Key Benefits:
- Reduced bounce rates
- Increased session time
- Higher conversion rates
- Better rankings for mobile and desktop
Focusing on these metrics not only helps with SEO but also boosts user satisfaction and trust.
Metric #1: Largest Contentful Paint (LCP)
What It Is:
LCP measures how long it takes for the main content (usually images or text blocks) to fully load. A fast LCP ensures users quickly see meaningful content.
Target:
LCP should be under 2.5 seconds for a good user experience.
Common Causes of Poor LCP:
- Slow server response
- Render-blocking JavaScript and CSS
- Large image files
How to Improve LCP:
- Use fast hosting or a CDN
- Optimise images (use WebP, compression, lazy loading)
- Minify and defer CSS and JavaScript
Metric #2: Interaction to Next Paint (INP)
What It Is:
INP evaluates how responsive your site is to user interactions like clicks or taps. It replaces the older metric FID (First Input Delay).
Target:
INP should be below 200 milliseconds for a seamless experience.
Common Causes of Poor INP:
- Main thread blocked by JavaScript
- Excessive use of third-party scripts
- Inefficient event handlers
How to Improve INP:
- Break up long tasks with requestIdleCallback()
- Remove unnecessary scripts
- Use modern frameworks optimised for performance (e.g., React 18, Vue 3)
Metric #3: Cumulative Layout Shift (CLS)
What It Is:
CLS measures how much content moves around while loading. A high CLS score leads to frustrating experiences like accidentally clicking the wrong button.
Target:
CLS should be less than 0.1.
Common Causes of Poor CLS:
- Images or ads without set dimensions
- Late-loading fonts
- Dynamically injected content
How to Improve CLS:
- Always define width and height for media
- Use font-display: swap
- Reserve space for ads and dynamic elements
Tools to Monitor Core Web Vitals
Google Search Console (GSC)
Shows Core Web Vitals reports for both mobile and desktop.
PageSpeed Insights
Provides scores and actionable fixes for each Web Vital.
Lighthouse
Generates in-depth performance audits for individual pages.
Chrome DevTools
Great for real-time debugging of layout shifts, load times, and responsiveness.
Web Vitals Extension
A browser extension for live testing Core Web Vitals while browsing.
Aligning Web Vitals With SEO Strategy
Core Web Vitals should be part of a broader SEO framework. They complement content relevance, technical SEO, and UX design.
Combine With:
- Mobile-first indexing
- Fast, secure hosting (HTTPS)
- Clean, crawlable architecture
- Intent-driven content
Optimising Core Web Vitals means your content gets discovered, loads fast, and keeps users engaged.
Conclusion
Core Web Vitals aren’t just metrics—they’re a blueprint for how users experience your website. In a competitive SEO environment, speed, responsiveness, and layout stability all influence whether visitors stay or bounce.
By improving your LCP, INP, and CLS scores, you’re signalling to Google—and your users—that your site is modern, fast, and trustworthy.
In 2025, investing in Web Vitals is investing in long-term rankings and customer satisfaction.
FAQs
Yes. They’re part of Google’s page experience signals used in its ranking algorithm.
LCP measures how quickly the largest element loads. INP measures how quickly the site responds to user interactions.
Yes. Slow or unstable pages may be outranked by equally relevant but better-performing competitors.
Very. Layout shifts are more noticeable and frustrating on small screens, making CLS crucial for mobile SEO.
Ideally, quarterly or after major changes to site structure, hosting, or design.