Agent skill

performance-audit

Run Lighthouse audit and verify Core Web Vitals. Use at project end before release. Triggers on "performance", "Lighthouse", "Core Web Vitals", "speed test", "page speed".

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Forks 31

Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/testing/performance-audit

SKILL.md

Performance Audit

Verify website performance meets Core Web Vitals standards.

Core Web Vitals Targets

Metric Target What it measures
LCP < 2.5s Largest Contentful Paint (loading)
FID < 100ms First Input Delay (interactivity)
CLS < 0.1 Cumulative Layout Shift (stability)

Audit Process

1. Run Lighthouse

bash
# Using Chrome DevTools
# 1. Open site in Chrome
# 2. DevTools > Lighthouse tab
# 3. Run audit (Mobile + Desktop)

# Or CLI
npx lighthouse https://localhost:3000 --view

2. Check Results

Target Scores:

  • Performance: > 90
  • Accessibility: > 90
  • Best Practices: > 90
  • SEO: > 90

3. Common Issues & Fixes

LCP Issues:

  • Add priority to above-fold images
  • Preload critical fonts
  • Use Next.js Image component
  • Enable image optimization

CLS Issues:

  • Set explicit width/height on images
  • Reserve space for dynamic content
  • Avoid layout shifts from fonts

FID Issues:

  • Minimize JavaScript bundle
  • Use dynamic imports for heavy components
  • Defer non-critical scripts

Checklist

Images:

  • All images use WebP format
  • Above-fold images have priority
  • Images have width/height set
  • Responsive images use sizes prop

Fonts:

  • Fonts loaded via next/font
  • Font display: swap enabled
  • No flash of unstyled text

JavaScript:

  • No unused dependencies
  • Dynamic imports for heavy components
  • No render-blocking scripts

General:

  • Lighthouse Performance > 90
  • No console errors
  • Mobile responsive
  • HTTPS enabled

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