Domain Authority
DADomain Authority is a third-party (Moz) metric estimating how likely a whole domain is to rank, based primarily on its backlink profile.
This is an important one to get right: Domain Authority is not a Google metric and Google does not use it in ranking. It's Moz's own proprietary score, and other tools (Ahrefs' Domain Rating, SEMrush's Authority Score) calculate their own similar-but-different versions. All of them are useful as rough, comparable proxies for site strength between competitors, but none of them is the number Google's algorithm actually computes internally.
No single standard definition
Domain Authority is a third-party metric (Moz), not something Google publishes or uses directly. Different tools calculate their own versions and the numbers aren't interchangeable.
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