PageRank simply explained

After Google stopped the publication of the PageRank value, PageRank as a ranking factor has almost fallen into oblivion. Contrary to widespread assumption, however, it is not dead, but has merely lost importance – and thus also attention – in favor of new ranking factors. Contrary to widespread assumption, however, it is not dead. It has merely lost importance – and thus also attention – in favor of new ranking factors.

SEO before PageRank

The first search engines were simply built and thus also easy to manipulate. Before Google revolutionized web search with its innovative algorithm, search engines simply analyzed how often the search phrase (keyword) appeared on a page. The more frequently, the better the page was ranked for that search term.

Search engine optimization before PageRank therefore consisted of repeating the keywords you wanted to rank for as often as possible on a page. Because the crawlers of the search engines did not only analyze the area visible to the visitor, but examined the entire source code for the search phrase, it was easy to manipulate the search results by hiding keywords in the source text.

Over time, the best positions for popular search terms were occupied by websites that engaged in keyword stuffing instead of offering users real added value. Sergey Brin and Larry Page wrote about this in their research paper at Stanford University:

“Anyone who has used a search engine recently, 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.”

The students at the time were looking for a solution to this problem and developed PageRank, which to this day serves as the basis for evaluating web pages for their search engine Google.

Page filed PageRank for a patent in 1997, which was registered to Stanford University. At that time the search engine “BackRub,” developed by Brin and Page in 1996, already existed; it has been known under the name Google since September 15, 1997.

Theory of PageRank

Sergey Brin and Larry Page wanted to provide the users of their search engine with search results sorted by relevance and thus offering real added value. In order to assess the quality and thus the value of web pages, they transferred the scientific citation practice to their search engine.

In the academic world, the importance of scientific works is assessed by citation frequency (impact factor). The more often a scientific publication is cited by other scientific publications, the more significant it is considered. Brin and Page transferred the methodology to the World Wide Web and evaluate the hyperlinks between websites as references. The more incoming links (backlinks) a web page has, the more important that page is.

What sounds so logical was a revolution in internet search that gave Google a real competitive advantage and is the reason why Google became one of the most well-known and valuable companies in the world within a very short time.

How PageRank works

The calculation of PageRank is no secret and can be found in the scientific paper by Brin and Page. In it, it says:

“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.”

The PageRank formula states that the link target (A) is considered by Google to be all the more important the more pages (Tn) point to it. However, the quantity of incoming links is not the only factor influencing the PageRank value. The higher the PageRank of a link source, the more strongly it is weighted by Google. A backlink that carries a high PageRank is therefore far more useful for search engine optimization than a multitude of weak references.

A referring page thus passes its PageRank on to the outgoing links (inheritance of PageRank). It should be noted that the value is divided among the outgoing links. A page with only one external link passes its entire PageRank on to the link target. If four links go out from the identical page, each page is assigned a quarter of the PageRank value (minus the damping factor).

The evaluation of a page thus arises recursively, in that the pages linking to it are evaluated. Link following is carried out according to the random surfer model, which corresponds to an internet user surfing randomly through the World Wide Web. The damping factor (d) simulates the probability with which a random visitor clicks on a link and ultimately ensures that link following is not continued infinitely.

The PageRank value is given on a scale from zero to ten, with ten being the highest PageRank. It is calculated individually for each single page of a domain and not just for the entire domain. For many years, Google publicly published the PageRank in a toolbar. After the public updating of the PageRank had already been discontinued a few months earlier, the toolbar was finally removed in 2016.

The scale from 0 to 10 is merely the public toolbar representation. Google's internal PageRank calculation is much more finely resolved and continues to be used (confirmed, among others, by Gary Illyes/Google).

Manipulation of PageRank

PageRank, too, was not invulnerable: keyword stuffing turned into link spamming at the beginning of the 2000s. Blogs, forums, and guestbooks were abused, link farms were created, and commercial link trading flourished – hyperlinks thus acquired a monetary market value.

To curb the manipulation, Google introduced the nofollow attribute in 2005. References marked with nofollow were not included in the PageRank calculation.

In so-called PageRank sculpting, the PageRank flow within a website was formerly controlled through the targeted distribution of dofollow and nofollow links. Google put a stop to this practice in 2009 – since then, nofollow links, too, consume a share of PageRank instead of passing it on in full to the dofollow links.

Today's significance of PageRank

Even though PageRank is no longer reported, this does not mean that Google no longer uses it. It is – albeit surely in an altered form – still part of the Google algorithm. Because in recent years, however, many further ranking factors have been added with which Google is able to measure the relevance and quality of a website, PageRank is by far no longer as significant as it used to be.

The basic idea of evaluating every link as a kind of recommendation has lost none of its appeal, even though criticism can certainly also be leveled at this methodology. Many points of criticism could, however, be eliminated or at least mitigated by the introduction of further ranking factors that, for example, place greater emphasis on user interest. And so backlinks are still among the most important ranking factors of all today.

With the PageRank value, however, an important metric for the quick assessment of web pages has also disappeared. Various SEO tools try to compensate for this loss with their own values (Page Authority from Moz, URL Rating from Ahrefs, etc.), which are, however, determined in highly different ways.

The most important questions and answers about PageRank

What is PageRank?

PageRank is an algorithm developed by the Google founders Sergey Brin and Larry Page and filed for a patent, used to evaluate web pages, which transfers the scientific citation practice to the World Wide Web. For many years, PageRank was given on a scale from 0 to 10.

How does PageRank work?

In order to calculate the value of a web page, the PageRank formula (see article) takes into account both the quantity and the quality of incoming links. The more and, above all, the stronger these backlinks are, the more important the page appears to be and the better it is ranked by the algorithm in the search results.

Does PageRank still play a role today?

Although the publication of PageRank was discontinued in 2016, it is still part of the Google algorithm. Because many further ranking factors have been added in recent years, however, its significance is by far no longer as high as it was at the beginning of the 21st century.

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