Core Web Vitals
A set of specific metrics defined by Google that measure real-world user experience for loading performance, interactivity, and visual stability.
Detailed Explanation
Core Web Vitals are Google's standardized metrics for measuring user experience. As of 2024, the three metrics are: LCP (Largest Contentful Paint, measures loading speed, target <2.5s), INP (Interaction to Next Paint, measures interactivity, target <200ms), and CLS (Cumulative Layout Shift, measures visual stability, target <0.1).
These metrics are measured by real users through the Chrome User Experience Report (CrUX) and are used as Google ranking factors. They are reported in Google Search Console, PageSpeed Insights, and Chrome DevTools.
Why It Matters
Core Web Vitals are Google ranking factors and directly measure user experience. Improving them improves both SEO and user satisfaction.
Real-World Example
A website improves LCP from 4.2s to 1.8s by optimizing images and adding a CDN. Their Google ranking improves, and bounce rate decreases by 20%.
When to Use
Measure and optimize for every page on your site. Set performance budgets for each metric and monitor regularly.
Advantages
- Google ranking factor
- Measures real user experience
- Standardized across all websites
- Available in free tools (Lighthouse, Search Console)
- Actionable with clear targets
Disadvantages
- Only three metrics (may not capture all UX aspects)
- Lab data may differ from field data
- Requires real traffic for field data
- Can be gamed (but Google uses real user data)
- Metric thresholds may change
Related Terms
Frequently Asked Questions
How do I measure Core Web Vitals?
Lab: Lighthouse (Chrome DevTools). Field: Chrome User Experience Report (CrUX), Google Search Console, PageSpeed Insights. Field data is more accurate as it reflects real user experience.
What is a good LCP score?
Under 2.5 seconds is "Good." 2.5-4.0 seconds is "Needs Improvement." Over 4.0 seconds is "Poor." LCP measures when the largest content element becomes visible.
What is CLS and how do I fix it?
CLS measures unexpected layout shifts. Fix by: setting dimensions on images/videos, using CSS aspect-ratio, avoiding dynamic content injection above the fold, and using font-display: swap for web fonts.
What is INP?
INP (Interaction to Next Paint) measures how quickly the page responds to user interactions (clicks, taps, key presses). Target: under 200ms. Optimize by reducing JavaScript execution time and breaking up long tasks.
Do Core Web Vitals affect all pages equally?
Core Web Vitals are measured per page, not per site. A site can have good CWV on some pages and poor on others. Google evaluates each page independently for ranking.