Perf Astro

Astro Performance Playbook

Astro-specific optimizations for 95+ Lighthouse scores.

Quick Setup

bashCopy code
npm install astro-critters @playform/compress

jsCopy code
// astro.config.mjs
import { defineConfig } from 'astro/config'
import critters from 'astro-critters'
import compress from '@playform/compress'

export default defineConfig({
  integrations: [
    critters(),
    compress({
      CSS: true,
      HTML: true,
      JavaScript: true,
      Image: false,
      SVG: false,
    }),
  ],
})

Integrations

astro-critters

Automatically extracts and inlines critical CSS. No configuration needed.

What it does:

• Scans rendered HTML for above-the-fold elements
• Inlines only the CSS those elements need
• Lazy-loads the rest

Build output shows what it inlined:

Copy code
Inlined 40.70 kB (80% of original 50.50 kB) of _astro/index.xxx.css.

@playform/compress

Minifies HTML, CSS, and JavaScript in the final build.

Options:

jsCopy code
compress({
  CSS: true, // Minify CSS
  HTML: true, // Minify HTML
  JavaScript: true, // Minify JS
  Image: false, // Skip if using external image optimization
  SVG: false, // Skip if SVGs are already optimized
})

Layout Pattern

Structure your Layout.astro for performance:

astroCopy code
---
import '../styles/global.css'
---

<!doctype html>
<html lang="pt-BR">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />

    <!-- Font fallback (prevents FOIT) -->
    <style>
      @font-face {
        font-family: 'Inter';
        font-display: swap;
        src: local('Inter');
      }
    </style>

    <!-- Non-blocking Google Fonts -->
    <link rel="preconnect" href="https://fonts.googleapis.com">
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
    <link
      rel="stylesheet"
      href="https://fonts.googleapis.com/css2?family=Inter:wght@400;600;700&display=swap"
      media="print"
      onload="this.media='all'"
    />
    <noscript>
      <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Inter:wght@400;600;700&display=swap">
    </noscript>

    <!-- Preload LCP images -->
    <link rel="preload" as="image" href="/hero.png" fetchpriority="high">

    <title>{title}</title>

    <!-- Defer third-party scripts -->
    <script>
      let loaded = false;
      function loadAnalytics() {
        if (loaded) return;
        loaded = true;
        // Load GTM, analytics, etc.
      }
      ['scroll', 'click', 'touchstart'].forEach(e => {
        document.addEventListener(e, loadAnalytics, { once: true, passive: true });
      });
      setTimeout(loadAnalytics, 5000);
    </script>
  </head>
  <body>
    <slot />
  </body>
</html>

Measuring

bashCopy code
npx lighthouse https://your-site.com --preset=perf --form-factor=mobile

See also:

• perf-lighthouse - Running audits, reading reports, setting budgets
• perf-web-optimization - Core Web Vitals, bundle size, caching strategies

Checklist

• astro-critters installed and configured
• @playform/compress installed and configured
• Google Fonts use media="print" onload pattern
• Third-party scripts deferred to user interaction
• LCP images preloaded in <head>