Why Performance Matters

A one-second delay in page load time can reduce conversions by 7%. Performance isn't just a technical metric — it directly impacts business outcomes and user satisfaction.

The 5 Essential Metrics

1. Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest visible element to render. This is the most important metric for perceived load speed.

Target: Under 2.5 seconds

How to improve: Optimize images, use CDN, implement lazy loading, and pre-load critical resources.

2. First Input Delay (FID)

FID measures the time between a user's first interaction and the browser's response. This directly affects how responsive your site feels.

Target: Under 100 milliseconds

How to improve: Minimize JavaScript execution time, break up long tasks, and use web workers for heavy computations.

3. Cumulative Layout Shift (CLS)

CLS measures visual stability — how much the page layout shifts during loading. Unexpected shifts are frustrating for users.

Target: Under 0.1

How to improve: Set explicit dimensions for images and ads, use CSS containment, and avoid injecting content above existing content.

4. Time to First Byte (TTFB)

TTFB measures how quickly the server responds to a request. It's the foundation of all other metrics.

Target: Under 200 milliseconds

How to improve: Optimize server response time, use caching, implement CDN, and optimize database queries.

5. First Contentful Paint (FCP)

FCP measures when the first piece of DOM content is rendered. It's the user's first visual feedback that something is happening.

Target: Under 1.8 seconds

How to improve: Eliminate render-blocking resources, inline critical CSS, and minimize server response time.

Tools for Measurement

Lighthouse — built into Chrome DevTools
Web Vitals — Chrome extension for real-user metrics
PageSpeed Insights — Google's performance analysis tool
GTmetrix — comprehensive performance reports

Conclusion

Tracking these metrics isn't just about numbers — it's about delivering a better experience to your users. Start measuring today, set targets, and continuously optimize.

Blogs

Building a Full-Stack E-Commerce Platform from Scratch

React Summit 2025: Key Takeaways and Highlights

Why I Switched from VS Code to Cursor

5 Performance Metrics Every Web Developer Should Track