Glossary

CDN

CDN (Content Delivery Network) is a distributed network of servers around the world that serves static files from the node geographically closest to the user. A file stored on a server in Kyiv is delivered from a node in London for a British user — without transatlantic round-trip delays.

What CDN caches

Images, CSS, JavaScript, fonts
Videos and large downloadable files
Static HTML pages (for JAMstack)

Benefits

Lower latency — physically closer to the user
Origin server offload — most requests are served by the CDN
DDoS mitigation — the CDN absorbs attack traffic at edge nodes

Popular options

Cloudflare (free tier available), AWS CloudFront, Fastly, BunnyCDN.