⚡ Core Web Vitals Demo - Real Performance Testing

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🎯 What are Core Web Vitals?

Core Web Vitals are Google's user experience metrics that measure real-world user experience. They are confirmed ranking factors for Google Search.

🖼️
Largest Contentful Paint (LCP)
0ms
Good: ≤2.5s | Needs Improvement: 2.5s-4s | Poor: >4s
Measures loading performance. Time when the largest content element becomes visible.
👆
First Input Delay (FID)
0ms
Good: ≤100ms | Needs Improvement: 100ms-300ms | Poor: >300ms
Measures interactivity. Time from user's first interaction to browser's response.
📐
Cumulative Layout Shift (CLS)
0
Good: ≤0.1 | Needs Improvement: 0.1-0.25 | Poor: >0.25
Measures visual stability. Amount of unexpected layout shift during page load.

🧪 Interactive Performance Tests

Click the buttons below to simulate different performance scenarios and see how they affect Core Web Vitals.

Test LCP (Largest Contentful Paint)

Test FID (First Input Delay)

Test CLS (Cumulative Layout Shift)

📊 Real Performance Comparison

Website Type LCP FID CLS Overall Score
Optimized E-commerce 1.2s 45ms 0.05 95/100
News Website 3.1s 78ms 0.15 72/100
Heavy Media Site 5.8s 450ms 0.35 28/100

🔧 How to Improve Core Web Vitals

🖼️ Improve LCP

  • Optimize images (WebP, compression)
  • Use CDN for static assets
  • Minimize render-blocking resources
  • Preload important resources

👆 Improve FID

  • Minimize JavaScript execution time
  • Use code splitting
  • Optimize third-party scripts
  • Use web workers for heavy tasks

📐 Improve CLS

  • Set size attributes for images/videos
  • Reserve space for dynamic content
  • Avoid inserting content above existing content
  • Use font-display: swap