Web performance audit
Web performance audits with Core Web Vitals, bottleneck identification, optimization recommendations. Use for page load times, performance reviews, UX optimization, or encountering LCP, FID, CLS issues, resource blocking, render delays.From its SKILL.md
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SKILL.md
2.5 KB, 616 tokens by cl100k_base, as published. Nobody here has run it
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
// 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
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
{
"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
What ships with it
Read from the repository
Just SKILL.md. No reference files, no scripts.
Gives 0 of the 12 instructions most audit compliance skills give in 616 tokens
Counted across 937 of the 1,487 authors here whose files we hold, read 2026-08-07
- Fetch latest guidelines before each reviewin 43 of 937, across 3 files
- Group findings by severityin 43 of 937
- Check files against all fetched rulesin 42 of 937, across 2 files
- Output findings in terse file:line formatin 41 of 937, across 3 files
- Ask user which files to review if none specifiedin 41 of 937, across 3 files
- Read specified files or prompt user for filesin 39 of 937, across 1 file
- Generate the audit reportin 33 of 937, across 30 files
- Assign a severity to every findingin 25 of 937
- Run automated accessibility scansin 23 of 937, across 13 files
- Output a markdown audit reportin 22 of 937
- Map findings to WCAG criteriain 20 of 937, across 10 files
- Confirm audit scopein 19 of 937, across 9 files
Grouped from the skills themselves: near-identical wordings counted once, and counted by distinct author, so one author publishing three of these counts once. Length counted with cl100k_base; the agent that loads this file may tokenize it differently.