What Is Domain Authority, and Who Actually Decides It?
Domain Authority is one company's prediction, built from link data and sold as a universal number. Here is what it actually measures, and the narrow job it does well.
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Domain Authority is a score from 0 to 100, published by a software company called Moz, that predicts how likely a domain is to rank in Google compared with other domains in Moz’s link index. Moz invents it, calculates it and publishes it, and Google neither produces the number nor stores it anywhere.
That is the whole domain authority definition, and it is worth holding onto before the score starts influencing what you buy. DA is not a quality rating, not a penalty check, and not a promise about traffic. It is a compressed summary of link data, and like every compression, it throws away detail you may have needed.
The score belongs to Moz, not to the industry
Moz built DA so an SEO could compare two sites without reading two backlink profiles line by line. It caught on, competitors answered, and now every major tool ships its own flavor: Ahrefs has Domain Rating, Majestic has Trust Flow and Citation Flow, Semrush has Authority Score. Each runs its own crawler, builds its own index of links, and applies its own arithmetic on top.
No shared unit sits underneath any of them. A DA of 38 means exactly one thing: given the links Moz managed to find, Moz’s model places this domain at that point on a curve drawn against everything else Moz knows about. Run the same domain through a rival tool and the figure usually moves, sometimes by a lot, and neither tool is lying. They measured different webs. That gap deserves proper attention before you quote a number to a client, and the DR and DA comparison covers where the two diverge hardest.
What actually feeds the number
Links, more or less exclusively. The model looks at how many unique root domains point at the site, how strong those linking domains are in Moz’s own terms, the raw volume of links, and Moz’s spam signals layered over the result.
Notice everything absent from that list. DA does not read your content. It has no idea about your traffic. It cannot tell whether the site loads, whether pages convert, or whether the business behind it still exists. A domain with forty genuine editorial links and no site at all can carry a respectable score. So can a domain whose links all came from one private blog network. The metric flattens two completely different situations into the same two digits.
It predicts competitiveness, not merit
Moz calculates DA with a machine learning model that hunts for the link-based formula best correlating with real Google results across a large sample of live searches. Read that slowly, because it is the crux: the score is tuned to predict ranking likelihood, not to measure quality. A domain scores well because sites shaped like it tend to rank, not because anyone judged it good.
Which makes “improve your DA” a slightly confused goal. You cannot edit the output. You can only earn the kind of links the model responds to, and when you earn them for real the rankings turn up whether or not the score has caught up yet.
The scale is relative, and it moves under you
DA is normalized against the rest of Moz’s index. The top is anchored to the strongest sites on the web and everyone else is fitted below them. When Moz recrawls, widens its index or retunes the model, scores shift across millions of domains at once. Your site can shed points in a week when you did nothing but publish as usual.
It is logarithmic too. Climbing from 15 to 25 is ordinary work. Climbing from 65 to 75 is a different sport entirely. Reading the scale as linear, and expecting the second ten points to cost what the first ten cost, is the most common way people misjudge their own progress.
Where DA genuinely earns its place
Triage, and it is a genuinely good use case rather than a consolation prize.
Working through a drop list with hundreds of candidates, you need something that separates “worth thirty minutes” from “skip” in about three seconds. An authority score does that job well enough, provided you treat it as a filter and never as a verdict. We score every domain on our curated expired domains list for backlinks, spam history and brandability for precisely this reason: the score narrows the field, then a person decides.
The failure mode is letting the filter become the decision. A high number earns a domain a place on your shortlist. That is all it earns.
Where it misleads buyers
Three ways, all of them routine on the aftermarket.
- Scores are buyable. Point a few hundred cheap links at a dead domain and the number climbs. It inflates easily because it is a link-only metric with a published methodology.
- Sitewide figures hide the shape of the profile. A domain often carries its entire strength on one or two old URLs. If those pages are gone and you redirect everything to a homepage, most of what you paid for leaks away.
- A clean score is not a clean history. DA will not tell you the previous owner ran a casino affiliate site or collected a manual action. That takes archive snapshots and an anchor text review.
Using it in five minutes without getting fooled
Pull the score, then immediately go and look at what produced it. Open the backlink profile and count linking root domains rather than links, because one site linking five hundred times is one endorsement. Read the anchor text for pharmacy, casino or loan terms in languages the site never spoke. Step through the Wayback Machine for every owner the domain has had, not only the most recent one.
If the links are real, the topic fits your plans and the history is boring, the score was telling you the truth. If any of those checks fail, the score was noise dressed as information, and you now know something no checker was ever going to tell you.
Key takeaways
- Domain Authority is a 0 to 100 score published by Moz, not by Google. It predicts ranking likelihood relative to other domains in Moz's index.
- The inputs are almost entirely link data: linking root domains, the strength of those domains, total link volume, and Moz's own spam signals.
- DA reads no content, measures no traffic and checks no penalties, so a domain with a comfortable score can still be worthless to you.
- Its real job is triage: deciding in seconds which expired domains deserve a proper manual review and which ones you can skip entirely.
- Because the scale is relative and the number is buyable, treat a surprisingly high score as a reason to look harder, not a reason to bid.
Frequently asked questions
Who invented Domain Authority?
Moz did. It is a proprietary metric calculated from Moz's own crawl of the web, created to give SEOs a single comparable figure for link strength. Competing tools built their own versions afterwards, which is why Ahrefs shows Domain Rating and Semrush shows Authority Score for the very same site.
Is Domain Authority the same as domain age?
No. Age is simply how long a domain has existed. Domain Authority is a prediction built from links. Old domains often score higher because they had years to attract links, but a ten-year-old domain nobody ever linked to scores close to zero, and a one-year-old site with real press coverage will beat it easily.
What is a normal Domain Authority for a small website?
Most small business sites and young blogs sit low on the scale, often in single digits or the teens, and that is normal rather than a problem. The scale is logarithmic and relative, so the bottom is crowded. What matters is how you compare with the sites already ranking for the terms you want.
Can I improve my Domain Authority directly?
Not directly, because you do not control the calculation. You can only earn links from stronger and more varied domains, which is what the model reads. Buying links to lift the number produces a score that impresses nobody and correlates with nothing, because the rankings the score is meant to predict never follow.