Have you been involved in SEO for more than a couple of years? You probably remember Google’s Toolbar PageRank.
Here’s what it looked like:
google toolbar pagerank
It showed the Google PageRank of every page you visited on a logarithmic scale from 0-10.
But even before Google officially removed support for Toolbar Pagerank in 2016, they had already ceased to update it for many years. For this reason, some SEOs view PageRank as an outdated and irrelevant metric that has no place in modern-day SEO.
Here’s a comment I found on another article about PageRank that sums up this way of thinking:
Pretty brutal. But here’s the thing: PageRank still plays a vital role in Google’s ranking algorithm.
How do I know this? Google said so.
(Gary Illyes works for Google. So that tweet is straight from the horse’s mouth, so to speak.)
But this year-old tweet isn’t my only evidence. Just a month ago, Gary Illyes spoke at a conference I attended in Singapore (here’s me with him!). In his talk, he reminded the audience that PageRank is still a part of their algorithm; it’s just that the public score (i.e., Toolbar PageRank) no longer exists.
With that in mind, the aim of this post is threefold:
To set the record straight about the importance and relevance of PageRank in 2018;
To explain the basics of the PageRank formula;
To discuss other similar metrics that exist today, which may make suitable replacements to the deprecated public PageRank “score.”
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What is Google PageRank?
PageRank (PR) is a mathematical formula that judges the “value of a page” by looking at the quantity and quality of other pages that link to it. Its purpose is to determine the relative importance of a given webpage in a network (i.e., the World Wide Web).
Google co-founders Sergey Brin and Larry Page devised PageRank in 1997 as part of a research project at Stanford University. They described their motivation as follows:
“Our main goal is to improve the quality of web search engines.”
That brings us to an important point: Search engines weren’t always as efficient as Google is today. Early search engines like Yahoo and Altavista didn’t work very well at all. The relevance of their search results left a lot to be desired.
Here’s what Sergey and Larry said about the state of search engines in their original paper:
“Anyone who has used a search engine recently telemarketing list can readily testify that the completeness of the index is not the only factor in the quality of search results. “Junk results” often wash out any results that a user is interested in. ”
PageRank aimed to solve this problem by making use of the “citation (link) graph of the web,” which the duo described as “an important resource that has largely gone unused in existing web search engines.”
The idea was inspired by the way scientists telemarketing list gauge the “importance” of scientific papers. That is, by looking at the number of other scientific papers referencing them. Sergey and Larry took this concept and applied it to the web by tracking references (links) between web pages.
It was so effective that it became the foundation of the search engine we now know as Google, and it still is.
How does Google PageRank work?
Here’s the full PageRank formula (and explanation) from the original paper published in 1997:
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. There are more details about d in the next section. Also C(A) is defined as the number of links going out of page A. The PageRank of a page A is given as follows:
PR(A) = (1-d) + d (PR(T1)/C(T1) + … + PR(Tn)/C(Tn))
Note that the PageRanks form a probability distribution over web pages, so the sum of all web pages’ PageRanks will be one.