What Is The Relative Strength Of An Internal Link?

Common SEO advice tells us that internal links are powerful. But how powerful exactly? In the complete guide on internal linking for SEO 2019, Brian Dean underlined that internal links are not nearly as powerful as external ones, but they still help to move the needle.

If internal links are only 1/10th as powerful as external links then perhaps a better use of one's time, energy, and resources should be used in building external links. What is the relative strength of an internal link? Stay tuned and you will find out!

We set up the test like this..

As a test setup, we used Google Doc published to the web as the external link. We assumed that an external link with a DA of 100 (Google doc) would be a lot more powerful than internal links built on a brand new site. By “more powerful” we mean it would take a lot of internal links to beat one external link and therefore a better use of one’s time should be spent building external links. 

We set up seven pages, each optimized for the same fake keyword and ran the experiment five times.

As a test setup, we

  1. Aimed an external link from a Google doc (link B) at page with #2 position (to simplify, let’s call this Page X)
  1. Created internal links (one per week) (without silo structure) at page with #3 position (let’s call this Page Y)
  1. Created internal links (one per week) (with silo structure) at page with #4 position (let’s call this Page Z)

To avoid confusion, we labeled..

  • External Google doc links as B.1, B.2, ...
  • Internal links without using silo structure as C.1, C.2,...
  • Internal links using silo structure as D1, D.2,..

Here is what we discovered

Week 1

The page with #2 position (labeled as Page X), which had a Google doc (B.1) aimed at it, moved to position #1 as displayed below. 

An internal link (without using a silo structure) C.1 was pointed at the page with the initial position #3 (Page Y). As of the 10th of July, page Y had dropped from the list but, interestingly, C.1 that pointed to it is now ranking at position #4.

An internal link (using a silo structure) D.1 was pointed at a page with the initial position #4 (Page Z). As of the 10th of July, Page Z moved from position #4 to #2 and Page D.1 is ranking position #5.

The page that initially ranked #5 (Let’s call it page L) moved two positions up and is ranking #3. Four of the initial listings have dropped at this stage.


Summary: 

  • Page X with a Google doc link aimed at it moved to position #1; 
  • Page Y with an internal link C.1 (without silo structure) pointed at it dropped, C.1 is ranking #4;
  • Page Z with an internal link D.1 (with silo structure) pointed at it moved to #2, D.1 is ranking #5;
  • Page L is ranking #3.

Week 2

Another internal link (using a silo structure) D.2 was sent to Page Z (position #2 on 10th July). As above, on the 17th July this page was listed #1, moving above the page with the link from the Google doc (Page X).

Another internal link D.3 was pointed at Page Y but this page still dropped from the results.

Page L is still ranking #3 on 17th July.

Next, we built 4 internal links and aimed them at 4 pages that previously dropped, however, they haven’t regained their ranking. We also built another external link from the brand new site to the page Y that previously dropped, but it hasn’t moved up either.

Summary:

  • Page Z with now 2 internal link D.1, D.2 (with silo structure) pointed at it, moved above Page X. Page Z is ranking #1, page X is ranking #2.
  • Page L is still ranking #3 on 17th July.

Week 3

On week 3, page Z (that had 2 internal links with silo structure D.1, D.2 pointing at it) was ranking #1, Page X (that had an external Google doc link aimed at it) was ranking #2, Page L maintained its position #3. They were followed by internal pages with silo structure.

Final Takeaway

Before running the experiment, we set an assumption that an external link is more powerful than internal links built on a brand new site.

Hence, we were pleasantly surprised to see that it took just two internal links (using a silo structure) to beat the external link - proving that internal links are relatively powerful.

This highlights that the strength of internal links is useful only within a silo structure.

Internal links without a silo structure are relatively weak. It is displayed in the above test as the page Y, that had an internal link without silo pointed to it, dropped from the listings and never returned.

When you are building a site architecture, we definitely recommend silo-ing. What does that look like? Let’s look at this example:

  • If you are selling red bicycles, the URL could look like this: yoursite.com/redbicycles. 

  • Then, you’ve got a blog post about red bicycles with the title “5 tips to find the best red bicycles” and the supporting URL: yoursite.com/redbicycles/5tipstofindthebestredbicycles. As you can see, the red bicycles page is in the URL structure. 

  • Additionally, there should also be a link going from the blog page “5 tips to find the best red bicycles” to the top level page. 

When most people write a blog, they are writing great content and hope that Google will make the connection between this content and that page. In a silo, you would remove the mystery for Google and let it know that this page is supported by this piece of content. 

We learned that two silo’d links beat the baseline link. This means that two posts properly silo’d and linking back to a target page will beat one baseline link. This is exciting because when you think about building a Google stack, there is more effort that goes into building a stack rather than building a couple of blog posts. Your own site or your client’s site probably have a lot of under-utilized blog posts that aren’t properly silo’d and they aren’t properly linking somewhere. Pro tip: you can immediately get an equivalent link strength just by reorganizing your site.