Core Web Vitals are Google's metrics for measuring real-world user experience on a website. They are part of the page experience signals used in search ranking.
The Three Core Web Vitals
LCP (Largest Contentful Paint)
Measures loading performance. The time until the largest visible element renders.
- Good: under 2.5 seconds
- Needs improvement: 2.5 to 4 seconds
- Poor: over 4 seconds
- Usually the largest image, video, or text block
INP (Interaction to Next Paint)
Measures responsiveness. The time from user interaction to visual response.
- Good: under 200ms
- Needs improvement: 200 to 500ms
- Poor: over 500ms
- Replaced FID (First Input Delay) in 2024
CLS (Cumulative Layout Shift)
Measures visual stability. How much the layout shifts while loading.
- Good: under 0.1
- Needs improvement: 0.1 to 0.25
- Poor: over 0.25
How to Improve LCP
- Optimize and preload the largest image
- Use a CDN for faster asset delivery
- Remove render-blocking resources
- Upgrade to faster hosting
- Use modern image formats (WebP, AVIF)
How to Improve INP
- Reduce JavaScript execution time
- Break up long tasks
- Use requestIdleCallback for non-critical work
- Defer or async non-essential scripts
- Optimize event handlers
How to Improve CLS
- Set width and height on images and videos
- Reserve space for ads and embeds
- Avoid injecting content above existing content
- Use CSS transform for animations (not top/left)
- Preload fonts to prevent FOIT/FOUT
Tools to Measure
- PageSpeed Insights. Lab and field data
- Chrome DevTools. Performance and Lighthouse tabs
- Search Console. Core Web Vitals report
- web-vitals JavaScript library. Real user monitoring
How Switch 2 One Helps
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