What is a CDN ?

CDN is short for content delivery network.

Content delivery networks (CDN) are the transparent backbone of the Internet in charge of content delivery. Whether we know it or not, every one of us interacts with CDNs on a daily basis; when reading articles on news sites, shopping online, watching YouTube videos or perusing social media feeds. A content delivery network (CDN) is a system of distributed servers or CDN peers ( network ) that deliver webpages and other Web content to a user based on the geographic locations of the user, the origin of the webpage and a content delivery server, 


This service is effective in speeding the delivery of content of websites with high traffic and websites that have global reach. The closer the CDN server or CDN peer is to the user geographically, the faster the content will be delivered to the user.


The CDN copies the pages of a website to a network of servers or CDN peers that are dispersed at geographically different locations, caching the contents of the page. When a user requests a webpage that is part of a content delivery network, the CDN will redirect the request from the originating site's server to a server or CDN peer in the CDN that is closest to the user and deliver the cached content. The CDN will also communicate with the originating server to deliver any content that has not been previously cached.

To minimize the distance between the visitors and your website's server, a CDN stores a cached version of its content in multiple geographical locations (a.k.a., points of presence, or PoPs). Each PoP contains a number of caching servers responsible for content delivery to visitors within its proximity.


In essence, CDN puts your content in many places at once, providing superior coverage to your users. For example, when someone in London accesses your US-hosted website, it is done through a local UK PoP. This is much quicker than having the visitor's requests, and your responses, travel the full width of the Atlantic and back.


Content delivery networks are part of an overall website strategy, but they are not a first step to take when improving your site. It is important to ensure you are doing all the things you can do before taking on the cost and complication of a content delivery network.

Lag times of any length frustrate web and mobile users accustomed to real-time digital experiences. According to Loadstorm :

  • 25% of users will abandon a website/content that takes longer than four seconds to load.
  • 74% of users will abandon a mobile(Content site that takes longer than five seconds to load.
  • 46% of users won’t return to a poorly performing website.


Content delivery network (CDN) traffic will carry nearly two-thirds of all internet video traffic by 2020


Source : Webopedia, Incapsula, Cisco, Radware, Varvy