Glossary /Authority & off-page
Domain Authority
A third-party score estimating a domain’s ranking strength. Useful for comparison, but not a metric any search engine uses.
Domain Authority is a Moz metric, and its equivalents — Ahrefs’ Domain Rating, Semrush’s Authority Score — are each vendor models built from a crawl of the link graph. Google does not use any of them and has said repeatedly that it has no site-wide authority score of this kind.
They are still useful, provided the use is comparative. Screening prospects, sizing up competitors and tracking a link profile’s direction are all reasonable applications. Setting a threshold and treating it as truth is not, because the number is a model output and the models disagree with each other.
The failure mode is optimising the proxy. Chasing the score produces links selected for what a tool will report rather than for whether a relevant audience will ever see them, which raises the metric and moves nothing else.