---
title: "CDN (Content Delivery Network) — monitoring glossary"
description: "A Content Delivery Network (CDN) is a globally distributed set of caching servers that serve static assets and (increasingly) dynamic content from a location…"
canonical: "https://lemwatch.com/glossary/cdn"
source: "https://lemwatch.com"
---

# CDN (Content Delivery Network)

> A Content Delivery Network (CDN) is a globally distributed set of caching servers that serve static assets and (increasingly) dynamic content from a location physically close to each user, dramatically reducing latency.

## Definition

 CDNs work by pulling content from your origin once and then serving subsequent requests from edge nodes around the world. A user in Tokyo requesting a CSS file hosted in London gets it from a Tokyo edge node instead of crossing the Pacific.

 Modern CDNs (Cloudflare, Fastly, AWS CloudFront, Vercel Edge) also run code at the edge — image resizing, A/B test routing, full HTML rendering — collapsing TTFB to under 100 ms globally.

## Why it matters

 Putting any public site behind a CDN is one of the cheapest, biggest performance wins available. It also provides DDoS protection, TLS termination, bot mitigation, and access logs — essentially free upgrades that come with the caching.

 See it in the product: [Performance monitoring](https://lemwatch.com/features).


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [TTFB](https://lemwatch.com/glossary/ttfb)
- [Page Speed](https://lemwatch.com/glossary/page-speed)
- [Lighthouse](https://lemwatch.com/glossary/lighthouse)
- [SEO](https://lemwatch.com/glossary/seo)
- [Sitemap](https://lemwatch.com/glossary/sitemap)
- [All monitoring checks](https://lemwatch.com/features)
- [Change Detection](https://lemwatch.com/glossary/change-detection)