PageRank is the foundational algorithm developed by Google co-founders Larry Page and Sergey Brin that measures the importance of a web page based on the quantity and quality of links pointing to it. First described in their 1998 research paper "The Anatomy of a Large-Scale Hypertextual Web Search Engine," PageRank treated each hyperlink as a vote of confidence, with the weight of that vote determined by the authority of the linking page itself.
The core insight behind PageRank is elegantly recursive: a page becomes authoritative by receiving links from other authoritative pages. This creates a self-reinforcing hierarchy across the web, where a link from a well-connected, trusted source transfers more value than a link from an obscure or poorly linked page. The algorithm models a hypothetical user who clicks randomly through links indefinitely, and the probability that this user lands on any given page at any moment becomes that page's PageRank score.
For many years, Google exposed a simplified version of this score publicly through its Toolbar PageRank, a visible 0-to-10 scale displayed in the browser. SEO professionals and webmasters used this metric extensively to evaluate the strength of potential link partners and to prioritize their link-building efforts. Google officially retired the public Toolbar PageRank in 2016, citing that it was being misused to commoditize links and that it no longer reflected the full complexity of how ranking signals were applied.
The retirement of the public score did not mean PageRank itself was abandoned. Google has confirmed repeatedly that PageRank, or a conceptual descendant of it, continues to operate internally as a core component of its ranking systems. The underlying principle - that links represent editorial endorsements and that those endorsements carry transferable authority - remains central to how search engines evaluate pages today. This transferred authority is now commonly referred to as link equity, also called link juice in informal usage.
Understanding PageRank helps explain why internal linking is a meaningful SEO lever. Because PageRank flows through links, a well-structured internal linking strategy can distribute authority from high-equity pages toward pages that need a ranking boost, without acquiring any external links. It also explains why third-party metrics like Domain Authority, developed by Moz, exist: they attempt to approximate the kind of site-wide link authority that PageRank originally quantified, filling the gap left by the removal of the public score.
For anyone working in SEO, PageRank is not merely a historical footnote. It is the intellectual foundation that explains why earning links from reputable, well-linked sources matters, why link quality consistently outweighs link quantity, and why the structure of a website's own internal links shapes how authority is concentrated and distributed across its pages.