# CDN

> A CDN is a content delivery network that keeps copies of your site's images, stylesheets and scripts on servers in different cities and countries, and serves them from the one closest to the visitor. Pages load faster and the main server carries less load.

- URL: https://radkod.com/en/glossary/cdn
- Publisher: RadKod
- Published: 2026-07-30

## What is a CDN?

CDN stands for Content Delivery Network. Your site's images, stylesheets and scripts are copied to servers in many places. When a visitor opens a page, those files come from the server closest to them.

Here is an everyday case. Your server is in Istanbul and a customer in Germany opens your product page. Without a CDN, each of the twenty product photos travels from Istanbul. With a CDN, they come from a server in Frankfurt. The shorter trip means a faster page. And on a sale day, when thousands arrive at once, your main server only handles the requests it has to.

## How does it work?

A CDN sits between your main server and the visitor. On the first request it fetches the file from your server and stores it at its own locations. Later visitors get the stored copy. When a file changes, the cache is cleared and the new version is spread out. Many CDN services also filter malicious traffic and handle SSL.

A CDN does not replace [hosting](/en/glossary/hosting). It adds to it. We explain how speed is measured in [Core Web Vitals](/en/glossary/core-web-vitals) and how to improve it in [site speed and Core Web Vitals](/en/blog/site-speed-core-web-vitals). Where it helps, we set up a CDN from the start, as described on our [web design](/en/services/web-design) page.

## Frequently asked questions

### Does every website need a CDN?

No. For a small site whose visitors are all in one city, the gain may be small. Image-heavy sites, sites with visitors from several countries and sites with sudden traffic spikes see a clear difference.

### Is a CDN expensive?

Free or low-cost plans exist for small and mid-sized sites. The price usually rises with the amount of data delivered.

### Does a CDN help SEO?

Indirectly, yes. Page speed affects user experience and Core Web Vitals, and a well set up CDN improves both.

## Sources

- [CDN](https://developer.mozilla.org/en-US/docs/Glossary/CDN), MDN Web Docs