Google’s Page Ranking System Explained
What is PageRank?
Pagerank (PR) is a score developed by Google to assign the importance of a webpage. It is calculated by considering the links (both quality, and quantity) pointing to a page. Pagerank scores can be between 0-10, which 0 denotes the minimum while 10 is the maximum.
Google uses PageRank data to determine the authority and relevance of webpages. It is numerical proof of page importance that Google uses as an important ranking factor.
PageRank doesn’t consider any page components like quality and the quantity of the content on a page. The only thing that affects the PageRank of a particular page is the backlinks pointing to that page.
If you have been in SEO for more than 5 years, you have very probably heard about Google PageRank (PR). Google used to display a score for each page on the web through its toolbar. Unfortunately, Google no more publicly shares this information anymore.
Google didn’t remove the PageRank from its algorithm but rather hid it.
Ranking pages on Google is a topic that is widely debated by SEO experts. Because we don’t have much information about Google’s ranking algorithm. It is kept as a big secret like the formula of Coke.
If Google shared everything about its algorithm, there wouldn’t be any Google. Because people could manipulate search engine algorithm to rank their websites overnight. This could hurt Google’s reputation which Google obviously doesn’t want.
The most powerful ranking factor is still links pointing to a website.
Today, even though we cannot see Pagerank scores, Google continues to use this information as a part of its algorithm. Here what Gary Illyes who works for Google says.
“Are we still using Pagerank in the rankings after 18 years?”
Gary Illyes at a conference in Singapore said that Google still uses PageRank but it is no longer a piece of information Google shares publicly.
It is not possible to exclude PageRank from being an important ranking factor since Google’s algorithm is based on backlink information and PageRank.
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History of PageRank
Let’s go back a little bit to learn more about how Google’s PageRank use started.
In 1995, 2 young people collaborated on a search engine called Backrub at Stanford University.
Unlike other search engines, the search engine made by these two young people, Larry Page and Sergey Brin, was based on a scoring system known as Pagerank, following links that determine the relevance of web pages.
The main reason they come up with a Pagerank system using the link information was the incapabilities of Yahoo and Altavista to provide relevant results.
These search engines (Yahoo and Altavista) just scanned the pages for keyword matching, which caused them to fail to compete with Google that is providing more relevant results.
When designing search engines with a research project, Sergey and Larry made a statement saying “Our main goal is to improve the quality of the web search engines” by considering the irrelevant results.
Sergey and Larry say about the status of search engines:
“Anyone who has recently used a search engine can easily say that the integrity of the index is not the only factor in the quality of the search results. Because of the trivial results, the actual results that the user is generally not interested in are not visible.”
In order to prevent search engines from listing historical irrelevant results, they found the solution they were looking for in a way that scientists used to measure the importance of their scientific articles.
Use of a scientist’s scientific article by another scientist as a reference. In other words, the more references used by different scientists, the greater the importance of the referenced article.
This technique has been so effective on the web that it has become the foundation of Google.
When Google was founded in 1998, they developed the search results on the patented PageRank ™ technique.
However, the Backrub they established before Google belonged to Stanford University and the patent of the Pagerank technique belongs to Stanford University, not Google.
How does PageRank Work?
If you wonder how PageRank works, the founders already give the formula to Google.
The below-shown formula is how Google calculated the PageRank. It was taken from the original article published in 1997.
We assume that page A has the T1… Tn pages referring to it.
D parameter is a damping factor that can be adjusted between 0 and 1.
Usually, we set D to be 0.85. (There are more details about D in the next section.)
Also, C (A) is defined as the number of links leaving page A.
Page Order of Page A is given as follows:
PR (A) = (1 ‐ D) + D ( PR ( T1 ) / C ( T1 ) +… + PR (Tn) / C (Tn))
Note that PageRanks creates a probability distribution on web pages, so be aware that the total of all the contributing web pages will create the final PageRank score.
Let’s summarize it in a way most of us can understand better.
Google takes three factors into account when calculating the PageRank value of a web page:
- Quantity and quality of incoming link pages
- Number of outbound links on each link page
- Page order of each link page
The PageRank formula also has a damping factor that simulates the possibility of the user clicking on links while browsing the web.
This value used in the PageRank calculation process is initially 0.85 for every website and decreases or increases by working with the following logic.
Links pointing to your site if clicked by the other website visitors are more valuable. Google uses link click information to define relevancy and legitimacy of backlinks.
Let’s say a website links to your site not from a single page but rather 10 different pages. In this case, the probability of clicking on the links will increase 10 times more.
With this logic, the high or low random click rate changes the initial 0.85 value, which is an aggregated value for the damping factor.
I hope I could explain how the PageRank score is calculated.
Every page on a website has a different PageRank score. This score is not a sitewide value but rather a page-specific metric used by Google. Every page that is in Google’s index without any exception has a PageRank score that is frequently recalculated and updated.
Why was the PageRank Score Removed?
You may be wondering why Google stopped sharing this amazing information with the users.
It’s very simple because the internet was starting to turn into a spam dump.
The higher the PR score of the site that gives backlink, the higher the PR score of the page that it links to automatically. For this reason, the internet was filled with spam links.
As I have said earlier, the PageRank scores just have been removed from the Google Toolbar not to be a piece of public information anymore.
People selling links, black hat SEOs used PR value as their best indicator to qualify their links. In addition, sites with high PR value started to sell links at once and a large industry emerged spontaneously.
Even more interestingly, the sites that sold links chose SPAM their websites to improve their PageRank in order to sell more links. The biggest link source was to comment under blog posts which are set usually “nofollow” by the webmasters.
Google’s Introduction of Nofollow Links
Google introduced Nofollow link attribution in 2005, in agreement with other major search engines, to avoid blog comments (Spam), which was a major problem at that time.
In this way, the issue of spamming through blog commenting is resolved. Today, almost all content management systems by default set comment links by default as nofollow.
However, Google’s solution to blog spam issue brought another problem. As one problem is resolved another issue popped up by mistake.
In the original formula, the PageRank aka link juice is transferred on a basis of even split between the outbound links. So if a page with PageRank value Y has 10 outbound links, the calculation would be as Y / 10.
But what if a site owner makes only 9 of these links nofollow and leaves 1?
In this case, the entire PageRank value of the page was transferred via a link, etc.
Finally, Google decided to root out the problem. In 2009 Matt Cutts cleared the issue by saying “We changed the flow of PageRank more than a year ago”.
Google made this change long years ago, and today the calculation of PageRank can really be different from what I have outlined in this post.
For example, the location of links on the page (such as header, footer) may affect the transfer value of a link. But what is certain is that the links without the nofollow tag cannot take advantage of the PR value more.
In 2014, John Mueller told webmasters that PageRank will no longer be updated and should not be paid attention. In 2016, Google Toolbar was completely removed.
But as I said at the beginning of the article, in my opinion, Google did not completely remove the PageRank score. It just adjusted in a way that spammers cannot be able to spam or abuse the system.