how to speed up website assets with a CDN

Using a CDN (Content Delivery Network) speeds up website assets by serving them from servers closer to your users instead of only from your origin server.

What to put on a CDN

Common static assets:

• Images
• CSS
• JavaScript
• Fonts
• Videos
• Downloads like PDFs

How it speeds things up

• Lower latency: users get files from a nearby edge server
• Less load on your origin: your main server handles fewer requests
• Caching: repeated requests are served faster from the CDN cache
• Better global performance: useful if you have visitors in multiple regions

Basic steps

1. Choose a CDN provider

   • Examples: Cloudflare, Fastly, AWS CloudFront, BunnyCDN, Akamai

2. Move static assets to CDN URLs

   • Instead of:
     • https://example.com/images/logo.png
   • Use:
     • https://cdn.example.com/images/logo.png
   • Or a CDN-hosted domain provided by the service

3. Set proper cache headers

   • For versioned assets, use long cache times:
     • Cache-Control: public, max-age=31536000, immutable
   • For HTML pages, use shorter or no-cache settings

4. Use file versioning

   • When you change an asset, change the filename or query string:
     • app.4f3a2c.js
     • style.css?v=12
   • This avoids users getting stale cached files

5. Enable compression

   • Use Brotli or gzip for text assets like JS and CSS

6. Optimize files before upload

   • Compress images
   • Minify CSS/JS
   • Remove unused code

7. Configure CDN cache behavior

   • Set rules for:
     • caching
     • TTL
     • cache key
     • origin pull
     • purge/invalidation

Best practices

• Keep HTML dynamic on the origin, cache only assets
• Use modern image formats like WebP or AVIF
• Load noncritical scripts with defer or async
• Use HTTP/2 or HTTP/3 if available
• Avoid overusing query strings if your CDN handles them poorly

Example setup

A simple setup might look like:

• Origin server: example.com
• CDN subdomain: cdn.example.com
• Static files uploaded to object storage or served from origin through the CDN
• HTML references assets like:

  <link rel="stylesheet" href="https://cdn.example.com/css/app.css">
  <script src="https://cdn.example.com/js/app.js" defer></script>
  <img src="https://cdn.example.com/images/hero.webp" alt="Hero">
  

Common pitfalls

• Caching HTML too aggressively
• Not versioning assets
• Forgetting to set CORS for fonts
• Serving uncompressed files
• Purging the cache too often

If you want, I can also give you:

• a Cloudflare-specific setup
• an AWS CloudFront setup
• or a step-by-step checklist for WordPress / React / static sites