Harmonic Centrality vs. PageRank
Harmonic centrality measures how close a node is to the nodes it can reach. Short paths contribute more, and unreachable nodes contribute nothing.
PageRank estimates importance flowing through incoming links: a link from a high-PageRank node can contribute more than a link from a low-PageRank node. So the metrics ask different questions. Harmonic centrality asks “how close is this node to the rest of the reachable graph?” PageRank asks “how much link-derived importance flows to this node?”
Common Crawl publishes both for its graph. Neither should be presented as Google’s own score or as a standalone measure of SEO quality. See how to read a Harmonic Centrality score or check a domain.
This answer describes the metric used by the HarmonicCentrality.org calculator. Common Crawl’s graph releases and methods can change; check the release shown with each score.