How Link Authority Works (PageRank)
Before Google, search engines ranked pages mostly by the words on them, which was easy to fake. The idea that made Google Google was to treat a link as a vote. That one move turned the whole web into a recommendation system, and its logic still sits under link authority today.
Links as votes
Google says plainly that it "uses links as a signal when determining the relevancy of pages and to find new pages to crawl." A link does two jobs at once. It is a path Googlebot follows to discover your page, and it is an endorsement: one site vouching that another is worth a look. On-page SEO is what you say about yourself. Links are what the rest of the web says about you, which is why they are harder to game and count for more.
The PageRank idea
PageRank is the 1998 algorithm from Larry Page and Sergey Brin that scores a page by the quantity and quality of pages linking to it. The twist that made it work: not every vote is equal. A link from a page that is itself well-linked counts for more than a link from an obscure one, because importance flows through the graph. A single link from a widely trusted source can outweigh dozens of weak ones.
The math includes a damping factor of 0.85, modeling a "random surfer" who keeps clicking links about 85% of the time and jumps to a random page the rest. It is a small detail with a big lesson: authority is not infinite. Each page passes along a share of what it has, so a page linking to hundreds of destinations gives each one less than a page linking to a handful.
A link from a well-linked page counts for more, because importance flows through the link graph. That single rule is the root of everything in off-page SEO.
Quality and diversity over raw count
Because votes are weighted, raw link count is a poor measure. What moves the needle is the number of distinct, relevant, trusted referring domains, not the total number of links. Five hundred links from one site still count as roughly one endorsement; five links from five respected, on-topic sites are far stronger. This is also why internal links matter: they pass the same kind of equity between your own pages, so the way you link your site together shapes which pages rank. Internal linking on-page →
What still holds up today
Google retired the public Toolbar PageRank score in 2016, and the live ranking system is far more complex than the original paper. There is no public number to optimize toward, and any third-party "authority" score is a vendor estimate, not what Google uses internally. But Google has confirmed it still uses PageRank as one of its core signals, so the concept is not history. It is a living part of ranking.
Two modern facts follow from the model. First, a redirect no longer bleeds authority the way it once did: Google has said 3xx redirects do not lose PageRank, so a clean permanent move preserves the votes a URL earned. Redirects and status codes → Second, because links are how Google discovers pages in the first place, a page nobody links to is hard to crawl and hard to rank. Crawling foundations →
The takeaway for the rest of Stage 1: earn links the way the model assumes they are given, freely, because your content deserved it. That is what the link-building and digital-PR chapters build on, and it is the same authority work that later helps an AI engine decide to name you.