What is Domain Authority and does it matter?
Domain Authority (DA) is Moz’s 1-100 estimate of how likely a site is to rank, based mostly on its backlink profile. Google does not use DA; it is a third-party approximation, and Ahrefs (DR) and Semrush (AS) have their own versions. Useful as a quick comparative gauge between sites, misleading as a goal: chase rankings and revenue, not a score.
DA exists because Google’s real authority signals are invisible, and the industry wanted a number. Moz built one: a machine-learning model trained to predict ranking likelihood from link data, scaled logarithmically (going from 20 to 30 is far easier than 70 to 80). Ahrefs’ Domain Rating and Semrush’s Authority Score answer the same question from their own indexes, which is why the three scores disagree about the same site and why none of them is "the real one": Google has repeatedly confirmed it uses no such single domain score.
What the scores are good for: rapid comparative triage. Evaluating a guest-post prospect, sizing up a competitor set, or screening link opportunities goes faster with a rough authority gauge, and used at that altitude (is this site roughly 20, 50, or 80?) all three metrics serve fine. They also give juniors and clients an intuitive progress proxy, which is simultaneously their value and their danger.
The danger: Goodhart’s law. When DA becomes the target, behavior warps: buying links from high-DA link farms, rejecting topically perfect links from honest small sites, reporting score movements that map to nothing in revenue. The scores update on index quirks, recalibrate without notice, and can be gamed in ways Google’s actual systems discount. Treat authority metrics like a car’s fuel gauge: glance at it, never steer by it. The dashboard that matters runs on GSC clicks, rankings for money keywords, and organic conversions.