# What is CDN – Content Delivery Network?

What is CDN – Content Delivery Network? A global network of servers that distributes content (images, video, JS) from the server closest to the visitor.

## How it works in practice

A CDN is the difference between a site that loads in 1.2 seconds and one that loads in 3.8. For a visitor in a city far from a US server, every image arrives from far away. With a CDN (Cloudflare, Fastly), images arrive from a local or regional server — a 60-70% improvement.

## Related metrics

- Core Web Vitals — a CDN directly improves LCP
- Page Speed — a CDN improves page speed
- SEO — a CDN improves ranking via Core Web Vitals
- Mobile UX — a CDN is critical to mobile experience

## Common misconception

'CDNs are only for big sites.' Cloudflare's free plan is enough for most stores — $0/month. Shopify includes a built-in CDN. WooCommerce + Cloudflare drives a meaningful improvement. A CDN is one of the best-ROI optimizations available.

## How to fix it

Site slow despite a CDN? (1) Check that the CDN is actually active (Cloudflare Dashboard → Cache Analytics), (2) Check cache-control headers — are images being cached? (3) Check image optimization — a CDN doesn't compress images automatically; it requires configuration.

## Real-world example

Computer-accessories store: page load time 4.1 seconds (US server, US customers). Added Cloudflare Pro ($20/month): load time 1.7 seconds. LCP went from 4.8s to 2.1s. Mobile organic traffic +31% within 60 days.

## Where to start

A CDN is priority 1 for technical optimization. Shopify: built in. WooCommerce: Cloudflare free plan + W3 Total Cache. 1 hour of setup = measurable improvement in Core Web Vitals, SEO, and CR.

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Category: Technology · From the [Jimmy OS KPI Glossary](https://jimmy-os.com/glossary/kpi.md) · Source page: https://jimmy-os.com/glossary/kpi/cdn-content-delivery-network