noun

CDN

SEE-dee-EN

CDN (noun) means a network of servers spread across many locations that keep copies of a website's files, so each visitor is served from somewhere geographically close rather than from one central machine. Example: “Once the images went on a CDN, the site loaded noticeably faster in Australia.”

noun

technical A network of servers spread across many locations that keep copies of a website's files, so each visitor is served from somewhere geographically close rather than from one central machine.

"Once the images went on a CDN, the site loaded noticeably faster in Australia."

"The CDN absorbed the traffic spike without the origin server noticing."

How to Use CDN

Learner’s notes

In plain EnglishA CDN keeps copies of a website around the world so it loads faster wherever you are.

When to use it

Take "a" before it in speech: "a CDN". Commonly paired with "edge" and "origin" — the origin being the site's own server.

Memory tip

A CDN sits in front of a site's own server rather than replacing it. When a cached copy is stale or missing, the CDN still fetches from the origin.

Trace the full origin ↓

Easily confused with

hosting → origin server proxy → DNS →

Common pairings

put it on a CDN CDN cache CDN edge serve from a CDN purge the CDN

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Fill the Gap

Can you complete this real example?

Once the images went on a _____, the site loaded noticeably faster in Australia.

Etymology

An initialism of content delivery network.

Origin: English

Synonyms

View more →

content delivery network content distribution network edge network

Frequently Asked Questions

What is the difference between a CDN and web hosting?

Hosting is where a site actually lives and where its pages are generated. A CDN sits in front of that, holding copies of files at many locations to serve visitors faster and reduce load on the host. A site can have hosting without a CDN, but not a CDN without something to originate from.

Does a CDN cache everything?

Not necessarily. Static files such as images, stylesheets and scripts are the easiest to cache. Pages that differ per visitor, such as an account dashboard, are usually passed through to the origin server or cached under stricter rules.

What does purging a CDN mean?

Purging tells the network to discard its stored copies so the next request fetches a fresh version from the origin. It is done after a file changes but the old version is still being served.