What Is a CDN and Do You Need One?

A Content Delivery Network (CDN) is a fleet of servers spread across the world that keep cached copies of your site close to your visitors. Instead of every request travelling to your one origin server, most are answered by a nearby edge — faster for users and lighter for your infrastructure.

How a CDN speeds things up

Distance costs time. A request to a server on another continent can add hundreds of milliseconds of round-trip latency no matter how fast that server is. A CDN solves this by placing edge nodes in data centres worldwide. When a visitor requests an image, stylesheet or script, the nearest edge serves a cached copy directly. The result is a lower Time to First Byte and faster overall page loads, especially for visitors far from your origin.

Edges also apply modern transport and compression automatically — often HTTP/2 and HTTP/3, plus Brotli — even if your origin server does not.

What gets cached (and what does not)

CDNs shine on static assets: images, fonts, CSS, JavaScript and downloadable files. These rarely change, so they can be cached aggressively at the edge. Truly dynamic content, like a logged-in dashboard or a checkout page, is usually passed through to your origin, though many CDNs can cache HTML for anonymous visitors with the right rules.

Content	Cacheable at edge?	Notes
Images, fonts, video	Yes	Ideal — large and rarely change
CSS & JavaScript	Yes	Version filenames so updates bust the cache
Anonymous HTML pages	Sometimes	With cache rules for non-logged-in traffic
Personalized / checkout pages	No	Served from origin to stay accurate

Resilience and security

A CDN is more than a speed tool. Because edges sit in front of your origin, they absorb load during traffic spikes — a product launch or a news mention no longer risks toppling one server. Most CDNs also provide DDoS mitigation, spreading and filtering malicious floods across their global capacity before that traffic ever reaches you. Many bundle a Web Application Firewall, TLS termination and automatic certificate management as well.

When it is worth it

Consider a CDN if any of these apply:

• Your visitors are spread across countries or continents.
• Your pages are media-heavy with lots of images or video.
• You get unpredictable traffic spikes or are a target for abuse.
• You want edge TLS, HTTP/3 and DDoS protection without reconfiguring your origin.

If you run a small site serving one city with modest, steady traffic, the gain may be marginal — though many providers offer a free tier that makes trying one low-risk. Popular options range from Cloudflare and Fastly to Amazon CloudFront, Akamai and BunnyCDN; they differ in pricing model, edge count and configuration depth rather than the core idea.

Getting the most from it

Set long cache lifetimes on versioned assets, keep dynamic routes out of the cache, and make sure your HTTPS redirects and security headers still apply at the edge. Then run a scan to confirm your headers, TLS and response times look right once traffic flows through the CDN.

Frequently asked questions

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