Hosting Tutorial & Guide

How Content Delivery Network (CDN) Affects SEO

updated on Oct 13, 2016
How Content Delivery Network (CDN) Affects SEO Content delivery network (CDN), acting as an important service of cloud hosting, is a system that contains copies of data distributed worldwide via dozens of web servers, to deliver the downloadable files like images, videos, scripts, CSS and HTML to global users with extremely fast loading time, in result to boost your search engine ranking and improve user experience for more visits and better conversion rate significantly.

However, the desperate advertising of content delivery network misleads many webmasters move to it for better performance and SEO without full evaluation; thus suffer from the drop of Google traffic seriously. BestHostingSearch (BestHostingSearch) is one of the victims. 2 weeks after moved the whole site to Internap CDN resold from Softlayer on Feb 24, the Google organic traffic was dropped by 44.8%.

In this case, we have come out an in-depth tutorial about CDN, helping you know what it is ultimately, along with some special tips when use it.

What's CDN

Content delivery network consists of hundreds of CDN nodes deployed in multiple geographic locations over multiple network backbones. These CDN nodes work with each other to response end users by transparently moving content to optimize the content delivery. Optimization includes reducing bandwidth costs, content load time, or improving international visibility of content.

The delivery process is, when there is a request for content, it will be routed to the closest CDN node which has the copy of content. In the background, there is a mechanism to synchronize content between CDN nodes and the source website. As a result, all global users can pull content from the CDN node nearby with the fastest loading time. Take an example for Yahoo News. Readers from New York visit the CDN node of Yahoo in New York, readers from San Francisco visit the CDN node in San Francisco, and readers from Japan visit the CDN node in Asia. They all read the complete same content by visiting the same //, but they actually get the content from different Yahoo edge servers.

How CDN Works

Typically, CDN has two different implementation, Origin Pull and PoP Pull.

Origin Pull

With Origin Pull, the requested content is pulled from your origin servers as needed and then delivered to your customers. You can set rules for how long your content is cached on the CDN nodes. CDN automatically tracks caching copy and only asks for an update if the cache is expired. This helps reduce the bandwidth and overhead on your web server.

PoP Pull

With Pop Pull, content is stored persistently on all CDN nodes globally, remaining available edging to international readers at all times. Compared to Origin Pull, Pop Pull needs you to manually update content, although you can manage content at a single place, then they will be synchronized automatically to all CDN nodes.

Origin Pull VS PoP Pull

It's a tradeoff between these two solutions.
  • Origin Pull is complete automated, but the cache of content on each CDN node is out of control. There is no opportunity to synchronize the content among CDN nodes. Once content is cached, it will be refreshed only when it's expired due to the configured caching time.
  • PoP Pull resolves the synchronization problem well, but it needs you to upload the content onto CDN manually in addition to more charge on the storage.

How BestHostingSearch Works With CDN

BestHostingSearch used Origin Pull mode of CDN, created a mirror website complete same as the main website with the sub domain Then removed the main domain from A HOST record and set it as a CNAME record mapping to Internap domain.

In our expectation and initial analysis, in this case, the requests to the main domain will be routed to Internap CDN entry, and eventually be routed to pull the content from

This did follow the instruction of using CDN Origin Pull mode in Softlayer as well as the information we found over the Internet. Yes, the website works correctly and successfully delivers content faster than before to global users by leveraging CDN.

How BestHostingSearch Suffered

After 2 weeks, we found the Google organic search traffic was dropped by 45%, as well as Google crawled pages daily and page downloading speed in Webmaster.
(Google Crawled Pages Dropped Daily)
CDN SEO – Crawled Pages Drop

(Google Page Downloading Speed Down)
CDN SEO – Crawled Pages Drop

Well, about revenue, we lost 30%+ daily. We had set the main domain back to our dedicated server and only left static files there such as JavaScript, CSS and images.

CDN SEO Impact Analysis

The root causes we analyzed in this disaster can be described from the following 3 aspects.

1. Google Page Fetch Speed Down from US

BestHostingSearch is an English site designed for US/Canada mainly. The most of traffics are from these two regions. With CDN, we found the Googlebot Fetch Speed is down from the Webmaster > Diagnostics > Fetch as Googlebot. This prevents the fleshness of BestHostingSearch to Google and leads the latest articles could not be indexed immediately. Google search likes fresh content well-known.

Yes, it makes sense for the downloading speed down. As BestHostingSearch hosted with a dedicated server in Dallas, US serving for requests nearby, the response speed is faster than the complicated Content Delivery Network whatever.

2. Site Targeting

With CDN, Google search cannot recognize the geographic target of BestHostingSearch well. It might not be the preferred site for readers from North American from the Googlebot’s perspective. Eventually, all keywords ranking were dropped to US/Canada region.

3. Mirror Site Indexed Incorrectly

As mentioned in the former part this article, we created to truly response to CDN nodes. Unfortunately, the SMART Googlebot indexed many web pages from this domain, although we still didn’t know how the Googlebot got the entry. In this case, CDN-WWW is complete duplicate to WWW which disobey the Google Quality Guideline potentially. was just a CNAME. Eventually, the ranking of WWW in Google search was dropped.

CDN Suggestions from BestHostingSearch

  1. Don’t easily move the main domain to CDN, although that’s the fastest way to get your site onto CDN.
  2. When you found the website loading speed is not reasonable, please try to optimize it using Google Page Analyzer instead of moving to CDN without sufficient business consideration and analysis.
  3. Put static files like JavaScript, CSS and Images to CDN only, and modify the reference in your website source code. This may have more works to do, but it’s trust-worth. If you’re using WordPress, Drupal or Joomla, it takes easy for the change as CDN migration is supported.
  4. When you pick a CDN provider, don’t trust the budget one. Akamai is always the best choice, and Internap is a good option although BestHostingSearch was suffered from it. These 2 providers have engaged in the field for over 5 years at least. You can easily search a CDN provider from Google, don’t do it for your main site until you have proven by yourself! There are TOO MANY scams and faking introduction about how CDN can benefit your website in SEO.

Web Hosting Recommendation

Bearing the above-mentioned tips in mind, the utilization of CDN can perform a positive effect for your website. Therefore, you'd better consider it when choosing a web hosting package. At present, there are dozens of web hosts that contain the CDN service into the hosting service. In the following, we have listed the top 3 options for you to choose.