Total Backlink Count vs. Unique Referring Domain Count

Understanding your backlink portfolio can help you to design strategies to meet your search engine optimization (SEO) goals. A backlink sends link equity, or a “vote of confidence” signal to search crawlers. This vote of confidence states that your content is authoritative enough to be cited and shared. A backlink posits the content as a valuable resource that could deserve to show up on a search engine results page (SERP) with the opportunity to gain visibility and traffic. A referring domain is the name of the website that hosts a link, and a referring URL is the specific page of the website that hosts the link. 

So, to clarify, the external backlink is the hyperlink that another site uses when referencing your authoritative content. The referring domain is the site that hosts the backlink. It is important to make this distinction because a single site could create many backlinks to your page with multiple referring URLs, but it would still only count as one referring domain.

Link Diversity

When it comes to a link building campaign, it is important to receive not only credible links but to earn a diversity of links to avoid red flags in your backlink profile. Having links to your site is important, but having a large number of your links only coming from one referring domain doesn’t necessarily strengthen your backlink profile. 

An illustrative example of this would be a situation in which you’re selecting a product by reading reviews. If you are deciding between two products, one that has multiple positive reviews from only one customer, or one that has multiple positive reviews from various customers, you may consider the diverse reviews to be more authoritative on the quality of the product because they come from a variety of different sources.

Additionally, having a profusion of backlinks from a single referring domain can result in a penalty from search engines as it may seem like inorganic black-hat SEO tactics, part of a link scheme, or part of a private blog network.

Link Relevance

A relevant link shows a topical similarity or association with the content of the page to which it’s linking. When analyzing a backlink portfolio, you aren’t just looking for the number of pages and domains linking to your site, you’re also analyzing the relevance of these domains and pages. Search engines, and Google specifically, analyze link portfolios looking for link schemes which are often indicated by a large number of irrelevant links. 

Relevance is tricky, as it can further be broken down with a few questions. Is the link relevant to the page on which it appears? Is it only relevant in context, while the page topic is a bit removed? Using our original apple example, consider this:

Your authoritative article on apples that discusses the vitamins and caloric content is beginning to earn links from a few domains:

1. Nutritionwebsite.com;
2. Anappleaday.com;
3. Racecarmadness.com.

Judging simply by the title of the domain, it is easy to see that the first two linking domains are going to be relevant to your apple selling company as they both seem to reside in the nutrition or food niche. The third referring domain doesn’t seem extremely relevant at first. 

However, you open the page with the link from the referring domain, racecarmadness.com, and find the referring URL is a page on race car driver diets. In the article, there is a section on fresh fruits indicating that drivers should eat apples for their nutritional content, and it includes a link to your apple page. 

The link to your page on apples is highly relevant in the context of fresh fruit, is a bit more removed from the page/referring URL in its entirety, and is even further removed in relevancy from the referring domain.

Search engines analyze links for relevancy and are able and adept at looking for contextually relevant links, though having at least some referring domains that are highly relevant with an obvious relationship to your niche is helpful. Relevance, link count, and contextual placement all matter, and that is partly why having a large, diverse backlink profile is important.