In 1998, Stanford University computer science students Sergey Brin and Larry Page published a research paper introducing Google, “a prototype of a large-scale search engine.” Brin and Page weren’t satisfied with existing web search options: they found human-generated databases too subjective (and expensive), while automated search engines returned too many junk results. One of the biggest issues they found with automated search engines was, while the internet continued to grow, “the user’s ability to look at documents has not. People are still only willing to look at the first few tens of results.”
Enter PageRank, an algorithm that calculates a quality ranking for web pages.
What is PageRank?
PageRank is an algorithm created by Google founders Larry Page and Sergey Brin that uses linking to determine a webpage’s importance. In 2006 Google replaced the original PageRank, and in the years since it has continued to update its algorithm. A version of PageRank is still in use at Google, and many additional factors now influence how Google determines a page’s ranking. Although Google has significantly modified its ranking algorithm, it still relies on links as a factor in assessing webpages’ usefulness.
The PageRank algorithm scores each page based on the path that leads from the page to a “seed” page. According to Google’s patent, selecting seed pages is a manual task done by humans. Seeds “need to be reliable, diverse to cover a wide range of fields of public interests, as well as well-connected with other pages (i.e., having a large number of outgoing links).” It lists The New York Times as an example of a high-quality seed page. The “closer” a page is to a high-quality seed page, the higher it ranks. (“Distance” is a measurement of how many clicks it would take to get to the seed.)
Factors that influence a webpage’s PageRank score
The original PageRank formula made use of three basic criteria:
- Number of backlinks. Also known as inbound links, backlinks are pages linking to yours. In theory, the more links pointing back to yours, the better. According to Google’s founders, the underlying assumption is “pages that are well cited from many places around the web are worth looking at.”
- Quality of backlinks. The Google algorithm factors in the PageRank scores of each of your backlinks. The higher the PR scores of your backlinks, the higher your page’s PR score will be.
- Number of outbound links on pages that link to yours. In determining how heavily to weight a given backlink, the Google algorithm considers how many other pages that page links to. If your backlinks link out to many different sites, this will dilute your search ranking.
The original Google PageRank algorithm
Here’s the original formula for calculating PageRank (PR) of page A, where d is a “damping factor” between 0 and 1 (Brin and Page usually set d to 0.85) representing the probability that a random user will “get bored and request another random page” and C is the number of outgoing links (citations). Pages T1 through Tn are the pages that link back to page A.
In this formula, your PageRank score is influenced by the perceived quality of the pages that link to yours. If pages with high scores link to your page, that has a positive impact. But if the pages that link to your page also link to many other pages, that can detract and cancel out some or all of the positive impact.
Criticisms of PageRank
Some of PageRank’s best qualities can also be criticisms:
1. Limited scope
Google’s “seed” method may deprioritize high-quality sites that are very niche. Google was built with the understanding most users won’t look past the first handful of search results. Its algorithms are designed to show the highest quality results at the top of the SERP, not to rank every relevant page on the web.
2. Can be manipulated
Since PageRank’s introduction, site owners have tried to manipulate their pages’ rankings by buying or trading links. Google calls this “link spam,” which is a direct violation of its policies. Google has tweaked its algorithm over the years to automatically detect suspicious links and to rank those results lower (or remove them from the SERP entirely). Due to the risk it carries, buying and selling backlinks is much less popular than in the early days of Google, but the practice continues to this day.
3. Favors older pages
The longer a page has been around, the more likely people are to have linked back to it, since links accumulate over time. But “mature” content isn’t necessarily better. This can lead to outdated links on the SERP. To combat this, Google now prioritizes newer content for certain topics; if a keyword triggers certain “query deserves freshness” signals, the search engine will automatically show more recent results.
How to improve your site’s PageRank
While PageRank no longer exists in its original form, Google still uses linking-based ranking systems. Here’s what to do to maximize your visibility:
- Accumulate backlinks. You can use careful link building to increase your site’s visibility on SERPs. The best way to accomplish this is to grow your backlinks organically by publishing high-quality content other sites will want to link to. As a small business owner, you might consider doing some public relations work to get noticed by media outlets. Use link analysis to see which sites already have external links to yours.
- Play by the rules. Avoid violating Google’s linking policies, or your site could be removed from the SERP. Any unnatural links could be flagged as spam; unnatural links can include backlinks from link farms (websites created solely to link back to yours) as well as low-quality paid links (like sponsored content or ads on another site that exist exclusively to build up backlinks).
- Use internal links. A good internal link structure can help Google see your site as a hub of information. Only use internal linking where it would make sense for the reader.
How frequently is PageRank updated and can it change quickly?
Google no longer uses the original PageRank algorithm, but linking still plays a large role in how Google ranks pages. There’s no real way to know how quickly Google’s evaluation of a page changes, since, as of 2016, Google no longer publicizes PageRank scores. If you’d like to keep track of your backlinks and other quality measures, you can use a third-party SEO tool.
Is PageRank the only factor that affects a website’s search engine ranking?
Linking is one of several factors Google’s algorithms use to rank pages on the SERP. The weight of other factors, including content freshness and site usability, are weighted according to the query.
Can a website with a high PageRank still rank lower in search results than a website with a lower PageRank?
Yes, it’s possible that a web page with a lower ranking score could end up outranking a higher-scoring page on the actual SERP, since link structure is not the only factor Google uses to rank webpages.
What is the impact of inbound links on PageRank?
Inbound links, also known as backlinks, are links that point to your site. PageRank was built on the assumption that the more inbound links a page has, the more important it is. But it’s not just the quantity of backlinks that matters. PageRank also looks at quality. So having just a few backlinks from sites with high PageRank scores is more valuable than having lots of links from sites with low PageRank scores.