PageRank was Google's original algorithm for scoring a page's importance, named after co-founder Larry Page, and it's genuinely foundational: it's the algorithm that Google's entire search engine was originally built around, treating each backlink as a vote weighted by the linking page's own importance.
The public-facing 0-10 PageRank score (visible in the old Google Toolbar) became a target for manipulation almost as soon as SEOs realized it mattered: link selling, PBNs, and other schemes built specifically to inflate a page's visible score. Google stopped updating the public score in 2013 and killed the Toolbar entirely by 2016, though PageRank itself, or some evolved descendant of the original concept, is still understood to function as one signal within Google's much larger modern ranking system, just without any public number attached to it anymore. Because there's no official score left to check, third-party metrics like Domain Authority or Domain Rating filled the gap as proxies, though none of them are PageRank itself, just independent attempts to estimate a similar underlying idea using each tool's own data and formula.
