What Is A CDN? When Should You Use A CDN For Your Website?

So, what is a CDN, exactly? How many types of CDN? And does CDN suit your website? In this article, you will find all necessary information as you wish.

What is a CDN?

It means as a system of servers worldwide (the number depend on each service provider) in charge of saving a copy of the static content within the site, and then distributing it to other servers (called PoP Points of Presence) and from those PoP, it will send to the user when they visit the website.

First of all, we have a look at different models between a website without the using of a CDN and a website used a CDN.

Without the using of a CDN

When users view a file without a CDN, this means that they send a request directly to the server having the website to access the file. This link of jvzoowsoreview.com is to access straight into jvzoowsoreview.com server, for example.


Within the using of a CDN

When a file distributed by the CDN, the user access to it, the closest PoP distribution with the users will pay content for the viewer. For example, you access this link to view the content of jvzoowsoreview.com on the CDN, so, if you are in US, the CDN PoP in US will deliver content to you.

cdn use-compressed

Some types of a CDN

When using some CDN services (not including CloudFlare or other similar proxy CDN services), you’ll see that they support some types of using CDN comprising:

Pull HTTP/Static

This type means that you declare the website domain name to use CDN or IP of the server. Then, the PoP CDN will automatically access to a website under that domain and save copies of all static content within the website (images, CSS files, JavaScript files, Flash, Video, etc). And then, you can access a specific file on the website with CDN links that they provide or use your own domain name for CDN. For example:

  • Original file: http://azbestreviews.com/wp-content/uploads/2016/03/Push-Leads-review-and-huge-bonus-compressed.jpg
  • CDN file: http://jvzoowsoreview.enator.netdna-cdn.com/wp-content/uploads/2016/03/Push-Leads-review-and-huge-bonus-compressed.jpg


This can be called with many different names. But, it has one thing in common is that instead of the PoP CDN will automatically collect the content in the website, you will download content needed to distribute straight through the CDN on their servers by common protocols such as FTP or HTTP. At present, FTP is the most one that they support.

And with this distribution method, you can save storage space on the server because there is nothing saved there.

Streaming CDN

Although the above types of CDN have the support of video file, but without live video streaming. So, this method will help CDN distribute content streaming from the server and then redistribute it to users to view in order to save bandwidth from the server of the original streaming. Or, you can choose to download streaming content directly to the server as Push CDN.

Advantages when using a CDN

So, once you understand how the CDN works, you’ll recognize that it has the advantages as following:

Saving bandwidth for root servers

Bandwidth from the network of the original root server just spends one time for handling that is to accept request from CDN PoP, then, the visits from users will only access content on the CDN, so the root servers will not spend more. Just when you proceed to delete the stored content on the CDN, the CDN PoPs will proceed to get content again, then, it will spend more.

Increasing the speed of the access times

Due to the nature of the CDN PoPs spreading across all continents, it will help your website access faster for remote users of the website server. For instance, jvzoowsoreview.com has server located in the US, if directly access to view an image in UK with the size of 300KB, it will take about 0.5 seconds (500ms). But, if jvzoowsoreview.com uses the CDN for static content within the support of PoP in UK, the user only takes 0.01 seconds (10ms) to view a file; it is even faster than that.

Similar to other users in other countries, the more your CDN has many PoP in many different countries, the more it is beneficial in increasing the speed of global website.

Saving capacity

If you use the method of Push CDN, this will help you save storage capacity of the server because everything has been uploaded straight to the CDN server. But, for safety, you should save the content in a certain place in order to prevent CDN services may get some problem.

Saving expense

Expense saved here is that the expense for bandwidth. Assuming that the server or your host package only supports a range of bandwidth that allows a certain month, when it’s over you will need to purchase or upgrade bandwidth. At that price, but bandwidth is not cheap, currently, average bandwidth price on a number of hosting provider is about 20.000 dong per GB, equivalent to $ 0.88. But the current CDN services will mostly cost about $ 0.05 or less, in some Asian PoP, if more expensive, at the highest, it just costs about $ 0.1 per GB bandwidth. So, instead you buy more bandwidth in the host, using the CDN will save you much more.

When should you use a CDN?

Using CDN offers you many benefits and it is one of the requirements that many websites have to use. But, it is not always necessary for any website. CDN is only useful when:

  • Server location of website is far from users.
  • Visits are large, so they consume a lot of bandwidth.
  • There are many visits in several different countries.
  • When using Load Balancing FailOver technique.

When is it unnecessary for using the CD?

As I said above, in most cases you do not need to use the CDN because not only it does not help your website faster, but slower. And one of the most common reasons is the host of the website located nearby users. For example, you have server in US and serves users in US , then you use CDN, but if CDN does not have PoP in US, your website will be slower because then your users will access in the other PoP further than the current root servers, so, it becomes slower.

Similar to proxy CDN service such as CloudFlare, website located server in US, but use it, users in US will access slower than normal.

Some notices when choosing a CDN service

When you go to choose a good, suitable CDN service for long-term using, you should notice for their PoP system. It is the best that you just select priority CDN services supporting PoP in the country where you have the most users. For example, if you choose CDN for website in US, you should prioritize CDN services having PoP in US such as CDNSun, CDN.Net, etc. Each provider has the Network for you to view their PoP system, so you should look carefully before using.

In addition, the second most important is the price and payment method. CDN services currently support two types of payment including the payment for how much you use (Pay-as-You-Go) or you pay a fixed fee per month to use the package. If your website does not cost you a lot of bandwidth, you should choose pay-as-you-go as a form of your payment. It will save you more because if buying a package, you may not use all of it.

The final notice is the speed; you can verify this by trying the service and conduct to ping to the address of CDN by the CA App Synthetic Monitor service to see whether it is really the optimal speed or not. Or, you can refer to some reviews of CDN on the internet.

Some free resources of CDN


This is a proxy service supporting free CDN quite common. If your website has located host in the United States or the European, the service will help you optimize the speed of your website greatly for visits from another country.

It’s unlike the simple CDN service that I have stated above, you cannot use a separate domain for CDN and cannot upload content to their CDN servers, but it will operate by using a middle proxy layer for the domain name. When users visit your website, they will go through a proxy layer and there, CDN available to deliver content in a page, the website link is unchanged.


This is a special service for WordPress users who have an installation of Jetpack plugin. It will automatically take the picture files on website to the CDN server of Photon and distribute to users to save bandwidth and page loading time.


This is the CDN service for Javascript libraries. For example, instead of self-host the jquery.js file of the jQuery library; you can use the CDN link of jsDelivr. Currently, it supports more than 1650 different libraries; virtually every popular JavaScript library has there. Simply using embedded JavaScript file to their link instead of self-host their own.

If you’re a WordPress user, you can install this plugin to allow it to change the JavaScript libraries being used in website to CDN link.

Google Hosted Library

Similar to jsDelivr, you can use the Javascript library links on Google’s CDN server to save bandwidth.

Some popular CDN services

  • Amazon CloudFront
  • MaxCDN
  • CDN77
  • Akamai CDN
  • CacheFly
  • CDN.Net
  • CDNSun
  • KeyCDN
  • EdgeCast
  • CDNlion
  • SoftLayer
  • WPPronto


How to use CDN

It is very simple for using CDN, after conducting to create CDN service; you just need to edit the original path of the static content on the website into the content path of CDN. For example:

01 <img src=”http://azbestreviews.com/images/logo.png”>

Change into:

01 <img src=”http://domain-name-cdn/images/logo.png”>

If you use WordPress, there are many plugins supported to self-change such as WP Super Cache, W3 Total Cache, CDN Enabler, etc.

Except for some proxy CDN services such as CloudFlare or Incapsula, it is not necessary to change anything because the domain name was requested through CDN due to you pointed DNS of domain into their services.

In this article, I’ve probably fairly mentioned in detail about CDN and I think that with all things above it’s really enough for you to understand the CDN.

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