What are CDN
Content Delivery Networks (CDN) are a number of servers located around the world delivering web content (images, videos, etc.) based on the visitor’s location. Web browsers take advantages of this by downloading this content simultaneously (as opposed to asynchronously).
(Left) Single server distribution
(Right) CDN scheme of distribution
src: https://en.wikipedia.org/wiki/Content_delivery_network
Speed
For many years already, Google has been clear regarding the effect of site speed (and consequently, page speed) on its ranking algorithm. Google has released its PageSpeed Insights tool which analyses the content of a page, returns a score and then provides you with suggestions for improvements.
The faster your page loads, the better your chances of being ranked. Chances are that you will rank better for content that’s hosted close to your visitors. A good CDN solution would allow you to be fast for visitors located in any location on the planet.
A good example of Content Delivery Network usage is YouTube: If you embed a YouTube (which also uses CDN) video on your website, your video will be loading faster than if you were hosting it yourself because, let’s face it, their servers are probably faster and closer to the visitors than yours.
Another good example is jQuery.js: A lot of websites today use the feature-rich JavaScript library, which makes HTML manipulation and animation (amongst others) much simpler. This library could be hosted on your server or hosted on Google’s servers, which would assure faster loading of the script.
Stability
A side effect of using Content Delivery Networks is splitting the load time among various servers on the networks, which means that your server ends up with more available resources (bandwidth, memory, etc.). If a server runs out of resources (RAM, bandwidth, etc.), it could crash and your website will go down. Google will penalise you if your website is not reliable and is down too much.
The use of CDN could help improve your global uptime by freeing resources you might need.
Before you go and start using Content Delivery Networks
Be aware that it is essential to have your site and CDN properly configured otherwise you might end up losing more than you are trying to achieve.
Since a CDN also allows you to serve the same content across multiple sources in different locations, it is important that Google doesn’t see it as duplicate content. As we already know, when we have duplicate content, it’s difficult for search engines to know which version(s) to index and rank in the search results. It’s important to tell the search engines which one is the original source.
In the case where you would host the whole web site on a Content Delivery Network, before using a CDN, the URL of the Contact Us section would be something like http://www.example.com/contact. After using a CDN, it would look like http://cdn.example.com/contact. These two separate URLs pointing to the same page might create important SEO issues caused by duplicate content.
The correct way to accomplish that would be to add Rel=Canonical tags to your concerned pages.
Using CDN solution can be extremely helpful, as long as it doesn’t kill your SEO efforts. I would recommend you monitor closely Google Webmaster Tools and the search results after such an implementation. A CDN service provider also needs to follow the best practices that not only improve loading time, but also provide positive results on rankings. Before choosing a provider, read reviews and ask the community what they think of their service.
Have you ever used a CDN? How did it impact your website and your ranking? Do you have a favorite provider?
