TrustRank comes from a 2004 Stanford and Yahoo! paper, "Combating Web Spam with TrustRank": humans label a seed set of trusted pages and trust flows outward along links. Google holds a patent titled "Search result ranking based on trust" (US 7,603,350), but nothing shows it runs a TrustRank score: unconfirmed. "Domain Authority" (a 1-100 score from Moz 3,024 ) and similar vendor metrics are estimates that Moz itself says are "not a direct ranking factor". Google confirms link analysis systems, including PageRank (Ranking Systems), and systems that "surface more authoritative pages". Use vendor scores to compare sites, never as a goal.