Top 10 Performance Optimization Tips for Frontend Apps

1. Minimize & Bundle Assets

Large JS and CSS files slow down page load time.

What to do :

• Use Webpack, Vite, or Rollup
• Tree-shake unused code
• Minify JS & CSS, Apply code splitting

Example:

// Dynamic import example (code splitting) import("./dashboard.js").then(module => {
  module.loadDashboard();
});

2. Use Preloading, Prefetching & Preconnect

Tell the browser which resources are important.

What to do:

• preconnect → external domains
• preload → critical CSS/JS
• prefetch → next-page resources

Example:

<link rel="preconnect" href="https://fonts.googleapis.com"><link rel="preload" href="/main.js" as="script">

3. Optimize Images & Media

Heavy images are one of the biggest reasons for slow loading.

What to do:

• Use WebP/AVIF formats
• Lazy-load non-critical images
• Compress using TinyPNG, ImageOptim

Example:

<img src="banner.webp" loading="lazy" alt="Banner Image">

4. Reduce JavaScript Execution Time

Too much JS blocks the UI thread and makes the UI feel slow.

What to do:

• Remove unused scripts
• Use Preact for a lighter alternative to React.
• Use Web Workers for heavy calculations

Example:

const worker = new Worker("worker.js");
worker.postMessage({ numbers });

5. Enable Browser Caching

Caching allows browsers to reuse assets instead of downloading them again.

What to do :

• Set appropriate Cache-Control headers
• Use ETag
• Implement Service Workers for offline caching

Example:

Cache-Control: max-age=31536000, immutable

6. Use a Content Delivery Network (CDN)

CDNs deliver static files like JS, CSS, and images from servers closest to users.

What to do :

• Lower latency
• Faster global performance
• Reduced server load

Example:

Common CDNs: Cloudflare, AWS CloudFront, Akamai

7. Lazy Load Components & Routes

Load only the parts of the app the user needs.

What to do :

• Route-based code splitting
• Dynamic imports
• Async components

Example:

const AboutPage = React.lazy(() => import("./About"));

8. Optimize CSS Delivery

CSS blocks rendering, so optimizing it improves initial load time.

What to do:

• Remove unused CSS (using PurgeCSS)
• Inline critical CSS
• Lazy-load non-critical styles

Example:

<link rel="preload" href="main.css" as="style">

9. Improve Runtime Performance

Make sure the app runs smooth after loading.

What to do :

• Minimize DOM updates
• Use memoization
• Virtualize large lists

Example:

const memoizedValue = useMemo(() => expensiveCalculation(data), [data]);

10. Monitor Performance Continuously

Regular monitoring ensures issues are caught early.

Tools:

• Google Lighthouse
• Web Vitals (Core Web Vitals tracking)
• Sentry
• New Relic
• Datadog