What Is A Content Delivery Network, And How Does It Work? Semalt SEO Experts Give The Answer

With Google's Page Experiment that is set to begin rolling out in June, site developers and business owners around the world need to start channeling more time and resources into improving their user experience.

Given the updates Google's Page Experiment focuses on loading, visual stability, and interactivity, we have a unique opportunity to audit our client's site performance. One of the significant facets of this will be reevaluating the sties web hosting and content delivery network setup. 

In this post, we will be explaining what Content Delivery Network (CDN) is, how it matters for SEO and how it works. 

Why does a website need CDNs

The average internet user doesn't pay much attention to how web pages work or what web hosting provider a website / business uses. Most internet users are most interested in factors that affect their experience (User Experience), as the quality of content, loading speed, and mobile-friendly and intuitive navigation. 

When dealing with e-сommerce sites, speed directly impacts how much money a website makes and losses. Did you know that pages that load between 0 to 2 seconds enjoy the highest conversions among e-сommerce websites? And the longer web pages load, the more they lose visitors and potential customers. In fact, the conversions on a webpage decrease by an average of 4.42%, with each additional second of load time between 0 and 5 seconds. 

Load time is also relevant to non-e-сommerce sites. The page loading speed drives visitors down the funnel by reducing their bounce rates. Websites that load in 1 second usually have a bounce rate of up to 7%.  Pages with up to 3 seconds latency period have about an 11% bounce rate. Pages that take up to 5 seconds to load have up to 38% of their visitors bounce. 

CDNs can help achieve optimal page loading speeds for both mobile devices and desktops. Cisco research shows that global CDNs are expected to carry up to 72% of all internet traffic in 2022. 

Without a CDN strategy, it would be next to impossible to be able to meet users' expectations or contend with your competition who use CDNs. 

What is CDN and Why Does It Work?

Websites that don't use CDN have to rely on one server to distribute their content to all their visitors. This means that a website visitor who is just a mile away uses the same server as a visitor who is on the other side of the world. This, of course, poses a severe problem.

On the other hand, CDN consists of a network of globally distributed servers. 

CDN providers are fond of placing their servers at strategic internet exchange points (IXPs), the physical location where internet service providers connect and exchange traffic, making it the perfect subway station to set up shop.

When you pay for a CDN service, you are sure to give allowances that allow you to distribute website content like audios, images, videos, CSS, JavaScript files, and HTML files to every server in the network. 

These servers can and will store cached versions of the content of your website, making it faster and readily available to website visitors regardless of their geographical location. If a user requests a page, the requested content gets delivered from the server closest to their geographical location. As a result, CDN reduces page latency as it minimizes the distance each request has to travel before it reaches a server with the requested data. 

As CDN improves the loading speed of pages, it also improves users' experience by optimizing the delivery of these services based on the type of content requested. Whether it is video streaming, large file downloads, dynamic content, or standard web content can be gotten to a user instantly. 

Asides from improving the loading speed, CDN also increases bandwidth and lowers the overhead costs for servers. 

How are CDNs important to our SEO efforts?

User experience Metrics

It's about time that you take your load time as seriously as we do. We live in a time where everyone is racing against the clock. With so many alternatives on the internet, no visitor will wait long to get information that they will read on another website that loads in a second. 

In 2005, Google released their mobile-friendly update, which significantly changed the SEO landscape by introducing mobile-friendliness as an "on or off" algorithm. 

July 2018, Google cleared the air by confirming that the landing page loading speed is a ranking factor.
May 2021, algorithm update is set to make your user experience even more important. 

Prior to this algorithm update, SEO pros were taken by surprise with these updates, and this made us conduct large-scale research to figure out the changes that came with search engine updates. But this time, we are fully prepared for this update because Google has told us exactly which metrics we should monitor and improve. 

The web. dev website gives us an overview of all the Core Web Vitals, and it has an essential tool we use in analyzing a site. When focusing on the load speed of a site, this tool provides concrete figures for the ideal FID and LCP speed. The CLS visual stability is also evaluated. 

To obtain optimal performance, the metrics must be under 100 milliseconds, 2.5 seconds, and 0.1 seconds, respectively. 

Advanced analytics

Premium CDN provides include an insight and analytics report as part of their package. One of the reasons why Semalt advises its clients to try out CDN is because they can collect critical information we would have to spend extra resources gathering. Information such as query-based traffic data, geographic, audience analytics, quality of service data, viewer diagnostics, and security event analytics all come as part of your package when you're using CDN. 

Many CDN packages offer an option for website owners to customize their insight dashboards, so monitoring these performance metrics becomes easy and automatic. 

Site Security

Do you experience denial-of-service (DDOS) on your website? CDN protects your sites from these attacks. Because it distributes content onto several servers, experiencing DDoS attacks is extremely unlikely, and your original servers are protected from DDoS attacks. 

Moreover, if or when a server in the network experiences more traffic than it can handle, new requests automatically get rerouted to other servers. The same concept applies when a server in the network gets attacked.

You must understand that your site's security indirectly affects your SEO performance. Usually, site security improves your user experience and builds trust in your brand and site, which makes it a priority for Semalt. 

What are the potential disadvantages Using CDNs in SEO?

While there are clear reasons why using CDN is excellent for your site, there are some disadvantages that you should know of.

Image hosting

A number of authorities in the SEO industry have aired their questions concerning the impact of CDNs on image rankings. In 2019, Barry Schwarts published an article analyzing Twitter interactions between a prominent SEO figure Lily Ray and John Mueller. In this discussion, Ray asked Mueller how SEO experts can retain the SEO value of images hosted on a CDN subdomain. Mueller replied by stating that it doesn't matter how the images are hosted. In fact, there are no SEO bonuses for having your images hosted on the same domain / host. 

That statement by Mueller cleared the air and debunked a widely helpful opinion within the SEO industry that hosting images on a CDN domain or a subdomain of a website hurts the SEO performance of its images. 

Yes, we understand that it isn't safe to assume that Google will see and interpret your subdomain as a part of your website. It's safer to think that Google will see your subdomain as a file archive, and it may be considered as an entity independent of your site. We can never be certain. 

Since Google's algorithm determines whether or not your subdomains are part of the main website, we are never certain which direction the chips will fall.

Duplicate Content

Another pitfall we do our very best to avoid has duplicate content as a result of using CDNs. This shouldn't be considered a real problem, but we must draw your attention to its possibility. Our clients do not have to worry about this because when set up correctly, CDN wouldn't give you any duplicate content issues. 

Using a canonical header setup stops this from happening by telling Google crawlers that the contents they see on the CDN are only a copy of the original. 


If you currently do not use a CDN and you're not satisfied with your current provider, you should consider hiring Semalt to help with your transition to CDN before the User Experience launches in May. 

The earlier, the better; you do not want to be left behind with this new update and have to work double-time to catch up to your competition when this new update begins to affect SERP rankings. With every algorithm launch, there are winners and losers. Choose what side you want to be on wisely.