Domain authority explained: what DA and DR actually measure
Domain authority is one of the most quoted metrics in SEO, yet it is also one of the most misunderstood. This guide explains what DA and DR really measure, how they are calculated, and how to use them when buying an expired domain.
What domain authority actually measures
DA and DR in plain terms
Domain authority is a score that estimates how likely a website is to rank in search results. Two providers dominate: Moz calls its version Domain Authority (DA), while Ahrefs calls its Domain Rating (DR).
Both scores run from 0 to 100 and both are built from backlinks. A higher score means the tool thinks the domain could rank more easily, but the number is an estimate, not a guarantee.
A metric, not a Google ranking factor
Google has stated that it does not use DA or DR in its algorithm. These scores are produced by third-party SEO tools, so they describe what a domain looks like, not how Google will rank it.
That distinction matters when you shop for names. A domain with a high score is not automatically trusted by Google, and a low score does not mean a name is worthless; it is a comparison shortcut, nothing more.
How DA and DR are calculated
The backlinks behind the score
DA and DR are both built mainly from the number and quality of backlinks pointing at a domain. The tools crawl the web, record who links to a name, and convert that link profile into a single score.
Moz trains its model on how pages actually rank in Google, which makes DA a predictive score. Ahrefs' DR is simpler: it measures the strength of a domain's backlink profile on a logarithmic scale from 0 to 100.
Why the scale is logarithmic
Moving from DA 20 to DA 30 is far easier than moving from DA 70 to DA 80. The scale is logarithmic, so each step gets harder as the score climbs, and high scores need many strong links.
The curve explains why low scores can climb quickly when strong links arrive, while scores near 90 barely move. Knowing this stops you from overpaying for a marginal difference in a domain's score.
Why domain authority matters for an expired domain
Comparing candidates before you buy
When several expired domains are for sale, domain authority gives you a fast way to shortlist them. A name with DA 45 and another with DA 15 are not equal starting points, even at the same price.
The score is a first filter, not a final answer. It points you to the names worth a closer look, where you then review the metrics of an expired domain such as referring domains.
A shortcut that still needs checking
Domain authority can hide problems. A name can score well while its links come from spam or irrelevant sites, so you should check a domain's history before trusting the number.
The same caution applies to a name's past. A domain that was penalized or used for spam can keep a respectable score on paper while its real potential is far lower than the metric suggests.
The limits of domain authority
What DA and DR do not measure
A domain authority score says nothing about traffic, content or revenue. A name can have a strong score and zero visitors, or a modest score and a loyal audience, because the metric only reflects links.
It also ignores a domain's reputation. A name with an old Trustpilot profile and a real brand history can be worth far more than its raw score, which is exactly why some buyers value Trustpilot and SEO together.
Why a high score is not enough
A high DA or DR does not transfer authority by itself. The value lives in the links still pointing at the name, so a domain that lost its links has little left to offer, whatever its score says.
This is why serious buyers look at the quality of the backlinks, not just the headline number. A single strong link from a trusted site can matter more than dozens of weak ones.
Domain authority vs page authority
A score for the domain, one for the page
Domain authority rates the whole domain, while Page Authority rates a single page. A strong page can sit on a weak domain, and the two numbers often tell a different story.
When you buy an expired domain, the domain-level score is usually the one that matters. You are buying the name and its links, not a single page that may have already disappeared.
Why the distinction changes your research
Checking only the page score can mislead you when a site is gone. An expired domain may show no live page score at all, so the domain metric is the only useful reference left.
That is why tools report both numbers side by side. Reading them together gives a more honest picture of whether a name still carries the strength it once had.
How to check domain authority before you buy
Where to find the score
Moz offers a free Link Explorer that shows a domain's DA, and Ahrefs shows DR in its own free tools. Both let you type a domain and read its score in a few seconds.
Several other platforms publish comparable scores, including Trust Flow and Citation Flow from Majestic. Because each tool computes differently, the same domain can show a different number in each.
What to do with the number
Use domain authority to rank your options, then verify the links and history behind each name before spending. The number is a starting point for research, never the whole decision.
If a name pairs a solid score with a clean history and a live Trustpilot profile, it can offer a head start that a brand-new domain simply does not have.