Reader, this is a safe space. It's okay to not know all this stuff.
At least that's what I'm telling myself because it took me more than a handful of conversations with web developers to fully grasp the concept. It's only right that I break it down for those dutifully Googling for answers now.
"A content delivery network or content distribution network (CDN) is a large distributed system of servers deployed in multiple data centers across the internet."
... Huh? Still not making much sense with all that jargon.
Let's try a different approach.
Imagine you have a website hosted in Denver, Colorado. We don't often think about websites as being in a physical location because the very promise of the internet is that it exists everywhere ... kinda like air and sarcasm. But ultimately, that website and all of the content assets within it are based somewhere.
Each time you go to load a webpage in your browser it is calling upon those assets to assemble in a view in front of you. That's all well and good if your website visitors are in Boulder, Colorado and your website assets are hosted in Denver. But if you have visitors coming from Boulder and Boston and Blagoevgrad and Beijing, that's a lot of distance for that content to travel.
Secondly, if you have a surge of traffic to your website, regardless of location, that's a lot of weight on any one server location. This is where a CDN comes in.
How a CDN Speeds Up Your Website
A CDN is a network of these servers based throughout the globe. When a visitor accesses your website -- whether they're from Boulder, Boston, Blagoevgrad, or Beijing -- the server closest to the visitor delivers the view of the website. When one person in the same part of the world accesses the website, that server makes a copy of the content so when the next person asks for it, it is delivered from around the corner instead of across the globe. Because there is less physical distance to travel, the content loads quicker. This shift is imperceptible to the end user who only experiences the page loading as requested.
Does a CDN Protect Against Outages?
Every marketer loves website traffic, but on occasion your website can get a rush of traffic all at once. Sometimes this happens naturally, like if you have a major story or piece of content that has gone viral. Sometimes there are more nefarious reasons for it, like a DoS attack, which intentionally brings a website down through a rush of external requests. A CDN on its own won't defend against attacks, which vary in size and type, but because CDNs distribute the traffic to multiple servers it can help reduce some of the weight on your primary server and keep the site responding.
Do I Need a CDN?
If you have your website, blog or landing pages built on HubSpot you actually already have CDN and don't need to worry about it. We built a world class CDN and a Web Application Accelerator (which is a little like a private fast lane) right into HubSpot from the start so you don't have to purchase or install anything extra.
If you are using a different CMS or blog, ask the provider if you have a CDN. If you don't have a CDN and are attracting traffic from different geographic regions -- whether those are across the country or across the Globe -- you may want to look into one. There are a number of CDN providers out there who could answer your questions and help you price it out.
So there you have it: a very untechnical, but hopefully helpful, beginner's guide to content delivery networks. If you'd like to dive into this more or get a list of CDN providers, this wikipedia article and its references aren't a bad next step.
Originally published Jul 1, 2014 12:00:00 PM, updated March 11 2019