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perf-astro

perf-astro

github.com/tech-leads-clubDevelopment7.1k284 installsUpdated 3d ago
Repository

About perf-astro

A performance playbook for Astro sites, aimed at developers optimizing build output and page loading. It covers critical CSS inlining, asset compression, layout guidance, and Lighthouse measurement.

Key features

  1. 01Critical CSS extraction and inlining
  2. 02HTML, CSS, and JavaScript minification
  3. 03Astro layout guidance
  4. 04Lighthouse performance measurement

Use cases

  1. 01Reducing render-blocking CSS on Astro pages
  2. 02Minifying assets in production builds
  3. 03Measuring mobile performance with Lighthouse

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/tech-leads-club/agent-skills --skill perf-astro

After installing, type/perf-astroin Claude Code to confirm it loaded.

Details

From the project README

Astro Performance Playbook

Astro-specific optimizations for 95+ Lighthouse scores.

Quick Setup

npm install astro-critters @playform/compress

// 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:

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:

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:

---
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

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>

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