Every SEO professional is familiar with PageRank.

PageRank is Google’s algorithm designed to measure the importance of a webpage based on the quality and quantity of webpages that refer to it. Pages that have higher PageRank (i.e., a large number of quality backlinks) are perceived as more authoritative by Google and rank better than those with lower PageRank.

For a long time, PageRank was a public metric — an SEO could download the Toolbar PageRank Chrome extension and estimate the importance of their webpages. However, in 2016, Google removed the extension from its browser and made the score unavailable, much to the dismay of SEO experts. Soon after this, many software providers began designing their own backlink-related indicators, providing the alternative to Google’s original PageRank score that SEOs can rely on.

Using Backlinks API, you could also develop a backlink analysis tool with indicators closely related to PageRank.

In its endpoints, you will discover various metrics estimating the authoritativeness of a page or domain based on its backlink profile. These metrics are rank, domain_from_rank, and page_from_rank. They can become an acceptable alternative to PageRank, as we use Google’s original PageRank formula when calculating them.

• domain_from_rank displays the rank of a domain referring to the target page or domain specified in a POST request;
• page_from_rank shows the rank of a page referring to the target page or domain specified in a POST request.

 
The definition of rank depends on the specific endpoint

Endpoint	Rank definition
Summary, Bulk Ranks	Rank of the target specified in the request
History	Rank of the specified target on a specific date
Backlinks	Rank that a given backlink passes to the target
Anchors	Rank that referring websites pass on to the target through the links with a certain anchor
Domain Pages, Domain Pages Summary	Rank of the specific page of the target website
Referring Domains, Domain Intersection	Rank that a referring website passes on to the target
Referring Networks	Rank that a referring network passes on to the target
Competitors	Rank of the competitor domain
Page Intersection	Rank that a certain backlink passes to the target
Timeseries Summary	Rank of the target on a given date

 

The rank values range from 0 (no backlinks detected) to 1000 (large number of quality backlinks).

The metrics are calculated based on the original method for node ranking in a linked database — the core principle behind Google’s PageRank algorithm. The exact formula is provided below.

How is the Rank of a page calculated?

To calculate the rank of a page, we use the original PageRank formula.

Here it is:

PR(A) = (1-d) + d (PR(T1)/C(T1) + … + PR(Tn)/C(Tn))

To understand what variables are used in it, we have to refer to Google’s explanation:

We assume page A has pages T1…Tn which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0 and 1. We usually set d to 0.85. …Also C(A) is defined as the number of links going out of page A.

In a nutshell, Google considers the following factors when calculating PageRank:

• The quantity of inbound linking pages;
• The number of outbound links on each linking page;
• The PageRank of each linking page;
• The damping factor, simulating the probability of a random user continuing to click on links as they browse the web (it is perceived to decrease with each link click).

 
Note that “PageRank can be calculated using a simple iterative algorithm and corresponds to the principal eigenvector of the normalized link matrix of the web.” It means that Google’s PageRank algorithm can calculate the PR of a page without knowing the definitive PageRank of the referring pages. This is because PageRank isn’t an absolute score, but rather a relative measure of a webpage’s quality compared to every other page in the linking database (or simply the web). You can learn more about the mathematics behind the algorithm in this article.

Backlinks API uses the same formula and thus takes into account the identical factors when calculating rank.

However, we always set a damping factor to 0.5

Having a rapidly growing backlink index with more than 121,000,000,000 pages allows us to calculate rank virtually for any page on the web.

Assume this article has backlinks from 3 pages. We know that:

• The first page has a PR of 400 and 32 outbound links in total;
• The second page has a PR of 300 and 40 outbound links in total;
• The third page has a PR of 200 and 5 outbound links in total.

 
Let’s calculate the PR of this page using the above variables:

PR of this page = (1 – 0.5) + 0.5 (400 / 32 + 300 / 40 + 200 / 5), which would be 30.5. Then, we should convert the number to integer, which is 30. That would be the rank of this page.

Please note that not all backlinks are equal. Depending on the types of backlinks, they may pass all of their PageRank or don’t pass it at all.

• A 301 link passes all of its PageRank to a destination page. For example, if the PR of Page A is 400 and this page is linked to Page B through 301 redirect, the PR of Page B will also be 400;
• A 302 link passes the same amount of PageRank as a regular backlink (see the formula above);
• a canonical URL passes all of its PageRank to a destination page;
• a link with the “nofollow” attribute doesn’t pass PageRank; however, it is still considered as a backlink by our system;
• a link with the “ugc” attribute doesn’t pass PageRank; however, it is still considered as a backlink by our system;
• a link with the “sponsored” attribute doesn’t pass PageRank; however, it is still considered as a backlink by our system.

How is the Rank of a domain calculated?

The rank of a domain is the normalized sum of PRs of its indexed pages. To provide it, the API first calculates the rank of each page the domain has, sums the values up, and then computes the log of the rank values to compress them to a narrow range on a logarithmic scale.
Each point on the scale is hence more difficult to achieve. For example, it is relatively easy to move from 100 to 101, but the 500 to 501 transition would require a lot more effort (and backlinks).

Domain Rank Scale

Rank Score	Description
25-35	this score is usually received by newly created domains with a small number of backlinks
200-300	this score is usually received by large domains with a big number of backlinks from authoritative pages
500+	this score is usually received by huge domains with a significant number of backlinks from authoritative pages; very few domains in our database have such rank scores