Website performance directly impacts user experience, conversion rates, and SEO rankings. In an era of instant gratification, every millisecond counts. Here's your comprehensive guide to optimization.
Why Performance Matters
The numbers speak for themselves:
Measuring Performance
Key Metrics
Tools for Measurement
Image Optimization
Images often account for the largest portion of page weight.
Modern Formats
<picture>
<source srcset="image.avif" type="image/avif">
<source srcset="image.webp" type="image/webp">
<img src="image.jpg" alt="Description">
</picture>Responsive Images
<img
srcset="small.jpg 400w, medium.jpg 800w, large.jpg 1200w"
sizes="(max-width: 600px) 400px, (max-width: 1000px) 800px, 1200px"
src="medium.jpg"
alt="Description"
>Lazy Loading
<img src="image.jpg" loading="lazy" alt="Description">JavaScript Optimization
Code Splitting
Break your bundle into smaller chunks:
// Dynamic imports
const Component = lazy(() => import('./HeavyComponent'));Tree Shaking
Eliminate unused code:
// Import only what you need
import { debounce } from 'lodash-es';
// Not: import _ from 'lodash';Defer Non-Critical Scripts
<script src="analytics.js" defer></script>
<script src="widget.js" async></script>CSS Optimization
Critical CSS
Inline critical styles, defer the rest:
<head>
<style>/* Critical CSS here */</style>
<link rel="preload" href="styles.css" as="style" onload="this.rel='stylesheet'">
</head>Remove Unused CSS
Use tools like PurgeCSS to eliminate dead code:
// postcss.config.js
module.exports = {
plugins: [
require('@fullhuman/postcss-purgecss')({
content: ['./src/**/*.html', './src/**/*.jsx']
})
]
}Caching Strategies
Browser Caching
# .htaccess
<IfModule mod_expires.c>
ExpiresByType text/css "access plus 1 year"
ExpiresByType application/javascript "access plus 1 year"
ExpiresByType image/png "access plus 1 year"
</IfModule>Service Workers
Cache assets for offline access:
self.addEventListener('fetch', event => {
event.respondWith(
caches.match(event.request)
.then(response => response || fetch(event.request))
);
});Server Optimization
Enable Compression
Gzip or Brotli compression reduces transfer size:
# nginx.conf
gzip on;
gzip_types text/plain text/css application/json application/javascript;Use a CDN
Serve assets from edge locations worldwide for reduced latency.
HTTP/2 or HTTP/3
Enable modern protocols for multiplexing and header compression.
Font Optimization
Font Display
@font-face {
font-family: 'MyFont';
src: url('myfont.woff2') format('woff2');
font-display: swap;
}Subset Fonts
Include only the characters you need:
/* Latin subset only */
unicode-range: U+0000-00FF;Monitoring and Continuous Improvement
Set up:
Conclusion
Performance optimization is an ongoing process, not a one-time task. Start with the highest-impact changes, measure results, and iterate. Your users—and your business metrics—will thank you.
