CDN (Content Delivery Network)

A CDN caches your static content (HTML, CSS, JS, images, fonts) on edge servers in dozens or hundreds of locations worldwide. When a visitor requests a page, the response comes from the nearest edge server (typically within 50-200ms of the user) rather than your origin server (which might be 1-2 seconds away).

Major CDN providers: Cloudflare (most popular for SMB; generous free tier), Fastly (developer-favorite; performance-tuned), AWS CloudFront (Amazon's CDN, integrates with S3), Akamai (enterprise-tier, $$$), Vercel's edge network (built into the platform), Bunny CDN (budget option, $1-10/mo for small sites).

Why CDNs matter for SEO: they directly improve TTFB (time to first byte), which directly improves LCP and FCP. Google's Core Web Vitals reward fast pages; CDNs are the cheapest way to make pages fast. For an international audience, a CDN can cut LCP in half — visitors in Japan loading a US-hosted page might see LCP 4s without a CDN, 1.5s with one.

What a CDN doesn't do: speed up server-side rendering (only static content is cached at the edge; SSR still hits origin), reduce JavaScript bundle size (it can compress with Brotli, but the bundle still has to download), or fix slow database queries.

Setup is usually trivial: point your DNS at the CDN, configure cache rules (most CDNs have sensible defaults), enable Brotli compression, enable HTTP/2 or HTTP/3, and add cache headers (`Cache-Control: public, max-age=31536000, immutable` for fingerprinted assets like `app.abc123.js`). Cloudflare's free tier handles 95% of small-business sites without further config.