What is a CDN?

A Content Delivery Network (CDN) is a system of geographically distributed servers that work together to provide fast delivery of Internet content. It’s designed to minimize latency in loading web pages by reducing the physical distance between the server and the user. A CDN allows for a quick transfer of assets needed to load content such as HTML pages, javascript files, stylesheets, images, and videos. A well-configured CDN can also help protect against common malicious attacks such as Distributed Denial of Service (DDoS) attacks. Over half of all internet traffic is served by CDNs.

How does a Content Delivery Network (CDN) Work?

To minimize distance between visitors and the website’s server, a CDN stores a cached version of its content in multiple geographic locations known as the points of presence (PoP). Each PoP contains caching servers designed to deliver content to visitors within its proximity.

For example, a visitor in the United States wishing to view content that originates from a UK-based server will have to deal with slow loading times if the request has to travel across the Atlantic Ocean. To eliminate the latency, a CDN will store the content in a local United States PoP.

The process of using a CDN is nearly transparent to the user. The only way a user would know if a CDN has been accessed is if the delivered URL is different from the URL that has been requested.

CDN services reduce load times in the following ways:

  • Instead of connecting to the location of a website’s origin server, a CDN allows users to connect to a data center that is geographically closer. The less distance spent traveling means the less time spent loading, plus it reduces load on the original server.
  • Hardware and software enhancements such as load balancing and solid state drives helps data reach the user faster.
  • A CDN will reduce the amount of data transferred by reducing file sizes by processes such as minification or file compression.
  • Sites using TLS or SSL certificates can be sped up by CDNs by optimizing connection reuse and enabling TLS false start.


Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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