PaperclipOrg
Claude Agent Skill · by Addyosmani

Performance

The performance skill identifies and resolves web performance bottlenecks through Lighthouse-based audits, prioritizing optimizations by their impact on Core We

Install
Terminal · npx
$npx skills add https://github.com/addyosmani/web-quality-skills --skill performance
Works with Paperclip

How Performance fits into a Paperclip company.

Performance drops into any Paperclip agent that handles this kind of work. Assign it to a specialist inside a pre-configured PaperclipOrg company and the skill becomes available on every heartbeat — no prompt engineering, no tool wiring.

S
SaaS FactoryPaired

Pre-configured AI company — 18 agents, 18 skills, one-time purchase.

$27$59
Explore pack
Source file
SKILL.md361 lines
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---name: performancedescription: Optimize web performance for faster loading and better user experience. Use when asked to "speed up my site", "optimize performance", "reduce load time", "fix slow loading", "improve page speed", or "performance audit".license: MITmetadata:  author: web-quality-skills  version: "1.0"--- # Performance optimization Deep performance optimization based on Lighthouse performance audits. Focuses on loading speed, runtime efficiency, and resource optimization. ## How it works 1. Identify performance bottlenecks in code and assets2. Prioritize by impact on Core Web Vitals3. Provide specific optimizations with code examples4. Measure improvement with before/after metrics ## Performance budget | Resource | Budget | Rationale ||----------|--------|-----------|| Total page weight | < 1.5 MB | 3G loads in ~4s || JavaScript (compressed) | < 300 KB | Parsing + execution time || CSS (compressed) | < 100 KB | Render blocking || Images (above-fold) | < 500 KB | LCP impact || Fonts | < 100 KB | FOIT/FOUT prevention || Third-party | < 200 KB | Uncontrolled latency | ## Critical rendering path ### Server response* **TTFB < 800ms.** Time to First Byte should be fast. Use CDN, caching, and efficient backends.* **Enable compression.** Gzip or Brotli for text assets. Brotli preferred (15-20% smaller).* **HTTP/2 or HTTP/3.** Multiplexing reduces connection overhead.* **Edge caching.** Cache HTML at CDN edge when possible. ### Resource loading **Preconnect to required origins:**```html<link rel="preconnect" href="https://fonts.googleapis.com"><link rel="preconnect" href="https://cdn.example.com" crossorigin>``` **Preload critical resources:**```html<!-- LCP image --><link rel="preload" href="/hero.webp" as="image" fetchpriority="high"> <!-- Critical font --><link rel="preload" href="/font.woff2" as="font" type="font/woff2" crossorigin>``` **Defer non-critical CSS:**```html<!-- Critical CSS inlined --><style>/* Above-fold styles */</style> <!-- Non-critical CSS --><link rel="preload" href="/styles.css" as="style" onload="this.onload=null;this.rel='stylesheet'"><noscript><link rel="stylesheet" href="/styles.css"></noscript>``` ### JavaScript optimization **Defer non-essential scripts:**```html<!-- Parser-blocking (avoid) --><script src="/critical.js"></script> <!-- Deferred (preferred) --><script defer src="/app.js"></script> <!-- Async (for independent scripts) --><script async src="/analytics.js"></script> <!-- Module (deferred by default) --><script type="module" src="/app.mjs"></script>``` **Code splitting patterns:**```javascript// Route-based splittingconst Dashboard = lazy(() => import('./Dashboard')); // Component-based splittingconst HeavyChart = lazy(() => import('./HeavyChart')); // Feature-based splittingif (user.isPremium) {  const PremiumFeatures = await import('./PremiumFeatures');}``` **Tree shaking best practices:**```javascript// ❌ Imports entire libraryimport _ from 'lodash';_.debounce(fn, 300); // ✅ Imports only what's neededimport debounce from 'lodash/debounce';debounce(fn, 300);``` ## Image optimization ### Format selection| Format | Use case | Browser support ||--------|----------|-----------------|| AVIF | Photos, best compression | 92%+ || WebP | Photos, good fallback | 97%+ || PNG | Graphics with transparency | Universal || SVG | Icons, logos, illustrations | Universal | ### Responsive images```html<picture>  <!-- AVIF for modern browsers -->  <source     type="image/avif"    srcset="hero-400.avif 400w,            hero-800.avif 800w,            hero-1200.avif 1200w"    sizes="(max-width: 600px) 100vw, 50vw">    <!-- WebP fallback -->  <source     type="image/webp"    srcset="hero-400.webp 400w,            hero-800.webp 800w,            hero-1200.webp 1200w"    sizes="(max-width: 600px) 100vw, 50vw">    <!-- JPEG fallback -->  <img     src="hero-800.jpg"    srcset="hero-400.jpg 400w,            hero-800.jpg 800w,            hero-1200.jpg 1200w"    sizes="(max-width: 600px) 100vw, 50vw"    width="1200"     height="600"    alt="Hero image"    loading="lazy"    decoding="async"></picture>``` ### LCP image priority```html<!-- Above-fold LCP image: eager loading, high priority --><img   src="hero.webp"   fetchpriority="high"  loading="eager"  decoding="sync"  alt="Hero"> <!-- Below-fold images: lazy loading --><img   src="product.webp"   loading="lazy"  decoding="async"  alt="Product">``` ## Font optimization ### Loading strategy```css/* System font stack as fallback */body {  font-family: 'Custom Font', -apple-system, BlinkMacSystemFont,                'Segoe UI', Roboto, sans-serif;} /* Prevent invisible text */@font-face {  font-family: 'Custom Font';  src: url('/fonts/custom.woff2') format('woff2');  font-display: swap; /* or optional for non-critical */  font-weight: 400;  font-style: normal;  unicode-range: U+0000-00FF; /* Subset to Latin */}``` ### Preloading critical fonts```html<link rel="preload" href="/fonts/heading.woff2" as="font" type="font/woff2" crossorigin>``` ### Variable fonts```css/* One file instead of multiple weights */@font-face {  font-family: 'Inter';  src: url('/fonts/Inter-Variable.woff2') format('woff2-variations');  font-weight: 100 900;  font-display: swap;}``` ## Caching strategy ### Cache-Control headers```# HTML (short or no cache)Cache-Control: no-cache, must-revalidate # Static assets with hash (immutable)Cache-Control: public, max-age=31536000, immutable # Static assets without hashCache-Control: public, max-age=86400, stale-while-revalidate=604800 # API responsesCache-Control: private, max-age=0, must-revalidate``` ### Service worker caching```javascript// Cache-first for static assetsself.addEventListener('fetch', (event) => {  if (event.request.destination === 'image' ||      event.request.destination === 'style' ||      event.request.destination === 'script') {    event.respondWith(      caches.match(event.request).then((cached) => {        return cached || fetch(event.request).then((response) => {          const clone = response.clone();          caches.open('static-v1').then((cache) => cache.put(event.request, clone));          return response;        });      })    );  }});``` ## Runtime performance ### Avoid layout thrashing```javascript// ❌ Forces multiple reflowselements.forEach(el => {  const height = el.offsetHeight; // Read  el.style.height = height + 10 + 'px'; // Write}); // ✅ Batch reads, then batch writesconst heights = elements.map(el => el.offsetHeight); // All readselements.forEach((el, i) => {  el.style.height = heights[i] + 10 + 'px'; // All writes});``` ### Debounce expensive operations```javascriptfunction debounce(fn, delay) {  let timeout;  return (...args) => {    clearTimeout(timeout);    timeout = setTimeout(() => fn(...args), delay);  };} // Debounce scroll/resize handlerswindow.addEventListener('scroll', debounce(handleScroll, 100));``` ### Use requestAnimationFrame```javascript// ❌ May cause janksetInterval(animate, 16); // ✅ Synced with display refreshfunction animate() {  // Animation logic  requestAnimationFrame(animate);}requestAnimationFrame(animate);``` ### Virtualize long lists```javascript// For lists > 100 items, render only visible items// Use libraries like react-window, vue-virtual-scroller, or native CSS:.virtual-list {  content-visibility: auto;  contain-intrinsic-size: 0 50px; /* Estimated item height */}``` ## Third-party scripts ### Load strategies```javascript// ❌ Blocks main thread<script src="https://analytics.example.com/script.js"></script> // ✅ Async loading<script async src="https://analytics.example.com/script.js"></script> // ✅ Delay until interaction<script>document.addEventListener('DOMContentLoaded', () => {  const observer = new IntersectionObserver((entries) => {    if (entries[0].isIntersecting) {      const script = document.createElement('script');      script.src = 'https://widget.example.com/embed.js';      document.body.appendChild(script);      observer.disconnect();    }  });  observer.observe(document.querySelector('#widget-container'));});</script>``` ### Facade pattern```html<!-- Show static placeholder until interaction --><div class="youtube-facade"      data-video-id="abc123"      onclick="loadYouTube(this)">  <img src="/thumbnails/abc123.jpg" alt="Video title">  <button aria-label="Play video">▶</button></div>``` ## Measurement ### Key metrics| Metric | Target | Tool ||--------|--------|------|| LCP | < 2.5s | Lighthouse, CrUX || FCP | < 1.8s | Lighthouse || Speed Index | < 3.4s | Lighthouse || TBT | < 200ms | Lighthouse || TTI | < 3.8s | Lighthouse | ### Testing commands```bash# Lighthouse CLInpx lighthouse https://example.com --output html --output-path report.html # Web Vitals libraryimport {onLCP, onINP, onCLS} from 'web-vitals';onLCP(console.log);onINP(console.log);onCLS(console.log);``` ## References For Core Web Vitals specific optimizations, see [Core Web Vitals](../core-web-vitals/SKILL.md).