What Is a CDN, and How Does It Work?

By Vladana Donevski

June 19, 2023

Every internet user wants to find their desired content easily and have it quickly load when browsing the web. We also wish to stay secure from spam and other malicious online attacks. Moreover, content owners and service providers strive to improve the user or customer experience and increase ad revenue and client retention.

CDNs help us find the page or video we are after and protect us from web-based attacks. But what is a CDN, and how does it do all that? Let’s find out.

CDN Definition

CDN is a group of geographically distributed and interconnected servers that provide efficient web content delivery. They transfer content from an origin server to the one nearest to the user that requested it. The internet service provider (ISP) delivers the requested content to the user the rest of the way. 

Some common types of content that CDNs transfer are:

  • Videos
  • Images
  • Stylesheets
  • HTML pages
  • JavaScript files

Besides bringing the desired content close to the user, CDNs also improve the user experience (UX) and overall web security. 

Before moving forward, let’s see how CDNs developed and what we can expect from them in the future.

History of CDNs: A Brief Overview

The history of CDNs kicked off during the late 1990s when the need to deliver vast amounts of data to internet users first started becoming a problem. Thus, the Content Delivery Network, which CDN stands for, came into existence. CDNs made over 20 years ago still handle between 15% and 30% of online traffic globally.

The first generation of CDNs managed both static and dynamic content, while the second generation focused on streaming audio and video material. The third generation is currently in development. We can expect it to be simple enough to be run by individuals with no tech experience. In other words –  mostly self-configured and capable of autonomic content delivery in the future.

Here are some key historical events regarding the evolution of CDNs:

  • The event that considerably accelerated the development of CDN technology was the 9/11 attack in 2001. Many people tried to access news websites at once on that day, which led to severe caching problems.
  • Big internet service providers started creating their own CDN functionalities before 2002 started.
  • In 2004, over 3,000 companies used CDNs.
  • Amazon launched its own CDN in 2008. 
  • In 2011, a newly-introduced CDN reduced delays in page loading (latency) by enabling the content to flow across its 38 data centers worldwide. 

How CDNs Work: Everything You Need To Know

Besides merely bringing desired content to end-users, CDNs have other equally important goals: providing that content quickly, affordably, and securely. 

Content delivery networks manage that by placing linked servers strategically at the points where different networks exchange data. In other words, CDNs connect to Internet Exchange Points (IXPs), where various internet providers converge to provide traffic originating from their networks. That way, CDNs take over the content and deliver it as close as possible to the interested user. 

When a user makes a request, the specialized CDN management software determines which server is the closest to the point where the request originated. Then, it delivers the desired content to such a server, which we call a CDN edge server. 

This strategy allows CDNs to reduce latency – the annoying delay when the page is loading – thus preventing time-out and load errors. The wider a CDN distribution in the physical world is, the shorter loading times for the end-user will be, regardless of where they are in the world. 

Since we keep mentioning servers, let’s define what they are before moving forward.

What Is a CDN Server?

In short, servers are high-powered computers or programs capable of:

  • Storing,
  • Processing,
  • Managing data we can find on a network. 

CDN servers provide services to other computer programs and their users, offering scalability and efficiency at the same time. They also deliver cached content stored on a CDN when a user request appears. 


Caching is a temporary file storage process that CDNs perform to let us access the requested content quickly. CDNs cache content at the edge of the network; thus, we can’t speak of CDN hosting since CDNs can’t replace traditional web hosting, only complement it.

CDNs can help websites struggling with performance issues since caching reduces hosting bandwidth. It can prevent service interruptions, making CDNs a desirable option for handling the inconveniences related to traditional web hosting.

What Is a CDN Provider?

A CDN provider is a business that owns data centers with servers located throughout the world. Their job is to store and load content on their servers upon user request.

There are countless time-saving CDN services these days, and they make fast browsing possible by saving website copies on thousands of proxy CDN servers worldwide. Thus, website owners that struggle with their website performance find CDN hosts very useful since visitors tend to leave the page if it doesn’t load in a few seconds.

What Does a CDN Do?

CDNs bring all sorts of content to web users in every corner of the world. This content could be pretty much anything, including:

  • Images,
  • Audio streams,
  • HD-quality videos,
  • Software such as OS, games, and applications.

In short, content delivery networks deliver everything you can expect to find online.  CDN providers make the content available by:

  • Hosting it on their server,
  • Hiring internet service providers or network operators to host CDN servers.

However, answering the question “What is a CDN about?” in more detail calls for a broader overview. So, let’s dive in.

Improves Load Times

As we mentioned, one of the key goals for CDNs is quick loading of desired content. And they make it possible by placing servers and storing cached content as near as possible to people browsing the internet. That way, the request doesn’t need to travel to the origin server and back, which could take a while. 

Moreover, CDNs compress files or minimize codes and markups in script files and web pages to speed up their travel time. Furthermore, they perform software and hardware optimizations. Finally, CDNs give a performance and security boost to websites using TLS/SSL certificates that keep the internet connection secure.

Reduces Data Transfer (Bandwidth) Costs

CDN servers enable the origin server to provide a reduced amount of data through caching. This lowers the bandwidth costs, which is one of the most significant expenses for website owners. 

Enhances Website Security

CDNs also help secure sensitive information against hackers and online attackers during web transactions. They do it by providing DDoS mitigation – a set of techniques and tools that block and absorb malicious spikes in traffic. 

Increases Content Availability

Traffic spikes and hardware malfunctions are inevitable. They can cause various inconveniences, including disabling visitor access to the website or bringing the web server down. Yet, a well-balanced CDN system can minimize the damage thanks to the following features: 

  • Load balancing spreads online traffic across several servers, successfully handling traffic spikes. To illustrate, think of several routes from point A to point B in the real world. When the quickest way gets congested, commuters take alternative routes, allowing everyone to get from point A to point B more quickly.
  • Even if a server malfunctions due to technical issues, users won’t notice that anything’s wrong with the data distribution. That’s because the intelligent failover system redistributes traffic to other available servers nearby, maintaining the service uninterrupted.
  • Another significant CDN benefit for end-users is undisturbed internet access, even in the unlikely event of the entire data center experiencing technical issues. If it comes to that, the system routes the online traffic to another available data center. 

Who Uses CDNs (and Who Probably Shouldn’t)?

Almost everyone uses CDNs. When you, for instance, stream a TV show on Netflix, buy something on Amazon, or post on Facebook, you harness the power of the CDN. 

However, it wasn’t like that in the early days of the tech. At the turn of the 21st century, only large companies could afford to use CDNs due to their high costs. Thankfully, those times are long gone, and everyone can benefit from the content distribution network technology at affordable prices today. There are even some free options available, though they are not as good as their paid counterparts, obviously.

So, which types of websites could make use of CDN? Lots, actually, but the two most common types would be:

  • eCommerce websites that sell goods nationally and internationally,
  • News websites because they tend to experience traffic spikes in case of breaking news and generally have large volumes of traffic, especially in the morning.

On the other hand, companies that do business locally should refrain from using a CDN for two good reasons: 

  • It can worsen the website’s performance by adding an unnecessary connection between the visitor and a nearby server.
  • There is the possibility of getting extra visitors that are highly unlikely to buy anything and will just clog up the server bandwidth.

With CDN explained this way, we can conclude that content delivery networks may be the right choice for you to promote your business globally, especially if it falls into one of the following categories:

  • Media
  • Mobile
  • Healthcare
  • Advertising
  • eCommerce
  • Entertainment
  • Online gaming
  • Higher education


To sum things up, here’s everything you need to know about CDNs in six short bullet points:

  1. They can handle any file in a digital format, including videos, images, stylesheets, games, and many other types of software.
  2. CDNs provide efficient data transfer by compressing files and connecting internet users to a data center closer to them from an origin server. 
  3. CDN service provides uninterrupted internet access if the nearby server or the entire data center experiences technical difficulties.
  4. They decrease loading times by caching (storing) files on servers located near the end-users.
  5. CDNs improve website security by keeping malicious attackers, spammers, and bots at bay.
  6. A content delivery network can help promote your business beyond your local city and state. But it would be best to take this opportunity cautiously because some businesses are best suited to local operations, and a CDN could make things worse.


What is a CDN, and how does it work?

CDN is a group of servers (powerful computers) working together to deliver the requested data to users in a particular geographical area. Servers temporarily store the content they receive. Thus, future end-users get the content quickly since their request doesn’t have to travel to the origin server – which could be thousands of miles away – and back.

What is an example of a CDN?

We’ve talked about CDN and its meaning for the online industries already, but here’s an example so we can define CDN better:

Let’s say you have a commerce website shipping goods anywhere in the world. You’ve hosted the site in New York and stored your files on the servers there. Now, a prospective customer from France wants to familiarize himself with your products.

The customer’s request goes to the server in NY that sends data back, which can take a while. If If a CDN was used instead, it would deliver the files to a server closer to the client first. That server would then temporarily store them so that this prospective buyer would get access to them quicker.

What does a CDN stand for?

CDN stands for Content Delivery Network. It’s a system consisting of interconnected servers located in a particular geographic area. Its mission is to deliver the content a user requests to the nearest server to them as soon as possible.

What is a CDN error?

A CDN error occurs when its edge server (the CDN server nearest to you) can’t access your origin server. It’s a common issue when a firewall is up on your server. If so, you need to disable the firewall to fix this error and use a CDN.

What is a CDN for dummies?

The CDN helps load internet pages, videos, and other forms of digital content as quickly as possible. Content delivery networks bring us fast page loading times, keep websites safe from online attacks, and reduce data transfer costs.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top