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Optimize your website’s performance with quick, actionable guides on Web Vitals.

Common causes of web vitals bad scores

Common causes of low LCP

• Large, unoptimized images
• Slow server response times
• Render-blocking resources (CSS & JavaScript)
• Lack of caching and CDN usage

Common causes of high CLS

• Images without width/height attributes
• Dynamically injected ads, banners, or embeds
• Slow-loading fonts causing “FOIT” (Flash of Invisible Text)

What causes a poor INP Score and how to diagnose it

What is INP?

Interaction to Next Paint (INP) measures how long it takes for the page to respond to user interactions (like clicks and taps).

A slow INP makes a site feel unresponsive and affects user experience.

How to check Your INP score

• 1️⃣ Use PageSpeed Insights → Check the “INP” section.
• 2️⃣ Chrome DevTools → Open DevTools → Performance Tab → Look for long tasks (>50ms)
• 3️⃣ Use the Web Vitals extension.

Common causes of high INP

• Heavy JavaScript execution blocking interactions
• Long-running event listeners
• Inefficient animations and DOM updates

Note: To improve INP, reduce JavaScript execution time, use web workers, and optimize event listeners.

How to use WebPageTest to find performance bottlenecks

What is WebPageTest?

WebPageTest is a free tool that provides detailed performance insights beyond what Lighthouse offers.

How to run a test in WebPageTest

• 1️⃣ Go to WebPageTest
• 2️⃣ Enter your website URL
• 3️⃣ Choose a test location & device
• 4️⃣ Click Start Test

What to look for

• ✅ LCP (Largest Contentful Paint) → See which element is delaying load
• ✅ CLS (Cumulative Layout Shift) → Find elements causing shifts
• ✅ Long main thread tasks (more than 50ms) → Identify slow JavaScript execution

Advanced Features

• Filmstrip View → See exactly when content loads
• Waterfall Chart → Find slow network requests

Final thoughts

Knowing exactly how to debug code and which tools to use is the first step to improving our performance metrics.

WebPageTest helps diagnose real-world performance issues. Run a test and find ways to optimize your site!

Stay tuned for more!

Thanks for reading :)