Ranking Systems

Google's founding idea, in Sergey Brin and Lawrence Page's 1998 paper "The Anatomy of a Large-Scale Hypertextual Web Search Engine", was to treat a link as a vote weighted by the importance of the page casting it. PageRank models a "random surfer" who follows links and, with probability 1 - d, jumps to a random page; the paper usually set the damping factor d to 0.85. 1 computes it for four pages.

PageRank by power iterationJavaScript

const links = { A: ['B', 'C'], B: ['C'], C: ['A'], D: ['C'] };
const n = 4, d = 0.85;
let pr = { A: 1 / n, B: 1 / n, C: 1 / n, D: 1 / n };
for (let i = 0; i < 50; i++) {
  const next = { A: (1 - d) / n, B: (1 - d) / n, C: (1 - d) / n, D: (1 - d) / n };
  for (const [from, outs] of Object.entries(links)) {
    for (const to of outs) next[to] += (d * pr[from]) / outs.length;
  }
  pr = next;
}
console.log(Object.entries(pr).map(([p, v]) => `${p}=${v.toFixed(3)}`).join(' '));

Output

A=0.373 B=0.196 C=0.394 D=0.038

A and B each have one inbound link, but A's comes from C, the most important page, which passes its whole vote to A; B gets only half of A's vote. D, with no inbound links, keeps only the random-jump share.

Google's ranking systems guide still lists PageRank, "one of our core ranking systems used when Google first launched", among many other systems it now documents by name. 1 shows the milestones.

Milestones in Google's documented ranking systems
Year	System	What it does	Status in 2026
1998	PageRank	Weights pages by links	Active, one of many link systems
2011	Panda	Demotes low-quality content	Part of core since 2015
2012	Penguin	Fights link spam	Part of core since 2016
2013	Hummingbird	Major ranking overhaul	Retired; systems evolved since
2015	RankBrain	Relates words to concepts	Active
2018	Neural matching	Relates queries to pages	Active
2019	BERT	Understands word combinations	Active
2021	MUM	Understands and generates language	Specific uses, not general ranking
2022	Helpful content	Rewards people-first content	Part of core since March 2024

Other active systems cover freshness, deduplication, passages, reviews, site diversity and spam (SpamBrain). Google retunes them together in broad core updates "several times a year".

E-E-A-T stands for experience, expertise, authoritativeness and trustworthiness, and Google calls trust the most important of the four. Quality raters assess it using Google's rater guidelines, but "search raters have no control over how pages rank." Google states that "E-E-A-T itself isn't a specific ranking factor"; its systems use a mix of signals that tend to identify such content, weighted more heavily for "Your Money or Your Life" (YMYL) topics such as health and finance.

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