PageRank

PageRank transformed web search by treating the internet's link structure as a massive citation network—the more important pages that linked to you, the more important you became. Larry Page and Sergey Brin's 1996 Stanford research project became Google, and their algorithm's recursive elegance made it the most successful search technology ever created.

The adjacent possible emerged from a simple insight. By 1995, the web had grown beyond human capacity to catalog, and existing search engines ranked pages by keyword frequency—easily gamed by stuffing pages with repeated terms. Brin realized that links were endorsements: a page linked by many important pages was probably important itself. The question was how to compute 'importance' when it depended on the importance of other pages.

Page and Brin began collaborating on 'BackRub,' a project to analyze the web's backlink structure. They worked with Scott Hassan and Alan Steremberg, who were critical to early development. The algorithm they created was recursively elegant: a page's importance depended on the importance of pages linking to it, which in turn depended on pages linking to them, and so on. Mathematical convergence ensured the calculation would stabilize.

The name 'PageRank' played on Larry Page's surname while describing its function. Page and Brin, with advisors Rajeev Motwani and Terry Winograd, published 'The PageRank Citation Ranking: Bringing Order to the Web' in January 1998. That April came 'The Anatomy of a Large-Scale Hypertextual Web Search Engine'—the paper that described Google's architecture.

By early 1998, Google had indexed 24 million web pages. Contemporary reviews found its results dramatically superior to Hotbot, Excite, and Yahoo. The algorithm's resistance to manipulation—you couldn't just add keywords, you needed genuine links from important sites—created a quality advantage that competitors struggled to match.

The cascade reshaped the internet. Stanford received 1.8 million Google shares for the patent license, selling them in 2005 for $336 million. PageRank became the foundation of a company worth over $2 trillion by 2024. The algorithm spawned an entire industry of search engine optimization—and cat-and-mouse games as Google continuously refined its ranking to resist manipulation.

As of September 2019, all PageRank patents have expired. The algorithm that once differentiated Google has become public knowledge—but the company's two decades of refinement mean the original patent barely describes modern search.