Astro Performance Skill

Purpose

Achieve 90+ Lighthouse scores and pass Core Web Vitals. Direct impact on SEO rankings and conversion rates.

Core Rules

• Preload LCP elements (hero images/text) with fetchpriority="high"
• Set explicit dimensions on all images and iframes to prevent CLS
• Use font-display: swap for all web fonts
• Self-host fonts and subset to reduce file size
• Defer third-party scripts until after load or user interaction
• Break up long tasks to keep INP under 200ms
• Use AVIF/WebP formats with responsive images
• Keep JS bundle under 100KB gzipped
• Implement edge caching with long cache headers for assets
• Monitor real user metrics with web-vitals library