How to use
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npx skills add https://github.com/secondsky/claude-skills --skill web-performance-auditBefore you start
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Original skill document
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Web Performance Audit
Conduct comprehensive performance audits and implement optimizations.
Core Web Vitals Targets
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | <2.5s | 2.5-4s | >4s |
| FID (First Input Delay) | <100ms | 100-300ms | >300ms |
| CLS (Cumulative Layout Shift) | <0.1 | 0.1-0.25 | >0.25 |
| INP (Interaction to Next Paint) | <200ms | 200-500ms | >500ms |
Performance Measurement
javascript
// Using web-vitals library
import { getCLS, getFID, getLCP, getTTFB } from 'web-vitals';
function sendToAnalytics({ name, value, id }) {
console.log({ name, value, id });
}
getCLS(sendToAnalytics);
getFID(sendToAnalytics);
getLCP(sendToAnalytics);
getTTFB(sendToAnalytics);Lighthouse Automation
javascript
const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');
async function runAudit(url) {
const chrome = await chromeLauncher.launch({ chromeFlags: ['--headless'] });
const result = await lighthouse(url, {
port: chrome.port,
onlyCategories: ['performance']
});
await chrome.kill();
return result.lhr;
}Optimization Strategies
Quick Wins (1-2 days)
- Enable gzip/brotli compression
- Minify CSS/JS
- Defer non-critical scripts
- Optimize images (WebP, lazy loading)
Medium Effort (1-2 weeks)
- Implement code splitting
- Add service worker caching
- Preload critical resources
- Eliminate render-blocking resources
Long-term (1-3 months)
- Architecture improvements
- CDN optimization
- Database query optimization
Performance Budget
json
{
"timings": [
{ "metric": "first-contentful-paint", "budget": 1500 },
{ "metric": "largest-contentful-paint", "budget": 2500 }
],
"resourceSizes": [
{ "resourceType": "script", "budget": 150 },
{ "resourceType": "image", "budget": 300 }
]
}Audit Checklist
- [ ] Measure baseline Core Web Vitals
- [ ] Run Lighthouse audit (mobile & desktop)
- [ ] Analyze real user metrics (RUM)
- [ ] Identify largest contentful element
- [ ] Check for layout shifts
- [ ] Review JavaScript bundle size
- [ ] Test on slow 3G connection
- [ ] Set performance budget
- [ ] Configure monitoring alerts
