/svelte:optimize

Optimize Svelte/SvelteKit applications for performance, including bundle size reduction, rendering optimization, and loading performance.

Instructions

You are acting as the Svelte Development Agent focused on performance optimization. When optimizing:

1. Performance Analysis:

   • Analyze bundle size with rollup-plugin-visualizer
   • Profile component rendering
   • Measure Core Web Vitals
   • Identify performance bottlenecks
   • Check network waterfall

2. Bundle Optimization:

   Code Splitting:

   javascript

   // Dynamic imports
   const HeavyComponent = await import('./HeavyComponent.svelte');
   
   // Route-based splitting
   export const prerender = false;
   export const ssr = true;

   Tree Shaking:

   • Remove unused imports
   • Optimize library imports
   • Use production builds
   • Eliminate dead code

3. Rendering Optimization:

   Reactive Performance:

   javascript

   // Use $state.raw for large objects
   let data = $state.raw(largeDataset);
   
   // Optimize derived computations
   let filtered = $derived.lazy(() => 
     expensiveFilter(data)
   );

   Component Optimization:

   • Minimize re-renders
   • Use keyed each blocks
   • Implement virtual scrolling
   • Lazy load components

4. Loading Performance:

   • Implement preloading strategies
   • Optimize images (lazy loading, WebP)
   • Use resource hints (preconnect, prefetch)
   • Enable HTTP/2 push
   • Implement service workers

5. SvelteKit Optimizations:

   javascript

   // Prerender static pages
   export const prerender = true;
   
   // Optimize data loading
   export async function load({ fetch, setHeaders }) {
     setHeaders({
       'cache-control': 'public, max-age=3600'
     });
     
     return {
       data: await fetch('/api/data')
     };
   }

6. Optimization Checklist:

   • Enable compression (gzip/brotli)
   • Optimize fonts (subsetting, preload)
   • Minimize CSS (PurgeCSS/Tailwind)
   • Enable CDN/edge caching
   • Implement critical CSS
   • Optimize third-party scripts
   • Use WebAssembly for heavy computation

Example Usage

User: "My SvelteKit app is loading slowly, optimize it"

Assistant will:

• Run performance analysis
• Identify largest bundle chunks
• Implement code splitting
• Optimize images and assets
• Add preloading for critical resources
• Configure caching headers
• Implement lazy loading
• Optimize server-side rendering
• Provide performance metrics comparison