What Is a Content Delivery Network?

Learn about the benefits and drawbacks of a CDN

A Content Delivery Network, otherwise known as a CDN, is a network of web servers distributed in different physical locations around the world that are used to speed up the delivery of content to end users and to provide redundant availability of services and content.

CDNs are owned by companies that either specialize in providing the service, or by telecom companies that offer CDNs in addition to their other business services. Website operators pay the these companies to use their CDNs to deliver content and services.

The servers that make up a given CDN are spread around the world, placed at the "edge" of the internet. "Edge," in this case, means that the servers aren't in centralized locations at the heart of the architecture of the internet, but rather are closer to users.

A cityscape lit up at night, with lines overlaid on it to represent data traffic
Busakorn Pongparnit / Moment / Getty Images

How CDNs Deliver Content Faster

When a website or service that uses a CDN publishes new content, that content is copied to every server in the CDN around the world. This is unlike a traditional website, which uses a single server or set of servers in one location.

Because the same content is spread across many servers, end users are able to access that content faster, load on the servers is reduced, and service quality general stays high, even when there's high traffic. In a high-traffic scenario, a website or service that uses only one server might crash. However, if the website is available on 10 servers in 10 locations, 2 or 3 servers going down won't take down the entire service.

When a user tries to access a website which uses a CDN, they are automatically directed to the "best" server for them based on the CDN's settings. The "best" server may be the one that is physically closest to the user and thus will deliver the content the fastest. The "best" server could also be the one that has the lowest traffic at that moment.

Generally speaking, the closer a CDN server is to the user accessing it, the faster the user should get the content. Content Delivery Networks are totally transparent to end users. End users get content delivered to them by CDNs every day, but never know.

Examples of a Content Delivery Network (CDN)

Content Delivery Networks were introduced in the late 1990s. The CDN that the average user might have heard of is Akamai, but it's far from the only CDN out there. Some prominent CDN providers include:

What Are the Benefits of a Content Delivery Network (CDN)?

The benefits of using a CDN for both website operators and end users include:

  • Faster delivery of content.
  • The ability to handle a larger number of simultaneous users.
  • Redundant backups so that one server going down doesn't take down the entire website.
  • Increased availability of content to end users.
  • The ability to more easily handle major, short-term spikes in traffic to the website.

What Are the Drawbacks of a Content Delivery Network (CDN)?

While CDNs have many benefits, they also have some drawbacks:

  • Using a CDN incurs additional cost for the website operator.
  • Deploying new content and features is a bit more complex for sites using CDNs.
  • Old versions of content can get cached on the CDN, so server caches sometimes need to be cleared after updates to make sure users sees the latest material.
  • Some countries that restrict access to information on the internet block CDNs, since they can be used to get around those restrictions. That means content delivered by a CDN may not be available in those locations.