PageRank
Google's original link-analysis algorithm, which scores a page's importance by the number and importance of pages linking to it, computed…
LinksDRDAAuthority ScoreDomain AuthorityDomain Rating
Third-party authority metrics
Vendor-calculated 0-100 scores estimating a domain's link strength — Ahrefs DR, Moz DA, Semrush Authority Score, Majestic Trust Flow — none of which Google uses.
In full
Each vendor computes its score from its own crawl of the link graph with its own model, so scores are not comparable between tools and can be manipulated by anyone who understands the model. Google has stated repeatedly that it has no domain authority metric of this kind. They are useful for coarse prioritisation and for tracking relative movement within one tool, and misleading whenever treated as a prediction of ranking ability.
Example
A prospect list is sorted by DR, then manually filtered because several high-DR domains turn out to be link-selling networks.
Related terms
Referring domains
The number of unique domains linking to a site or page, generally a more meaningful measure of link popularity than raw backlink count.
Keyword difficulty
A vendor-specific 0-100 score estimating how hard it is to rank on page one for a query, usually derived from the link profiles of current…
Link profile
The aggregate characteristics of all links pointing to a site: source diversity, anchor text distribution, follow ratio, topical relevance…
Backlink
A hyperlink from one website to another, historically the strongest external signal search engines use to judge a page's importance and…