Domain metrics

Domain Authority (Moz)

Moz's 1–100 score that predicts how likely a domain is to rank in search results, computed by a machine-learning model over Moz's own link index. A comparative, logarithmic-feeling number, not a Google metric.

Domain Authority (DA) is a score from 1 to 100 published by the SEO software company Moz. Moz describes it as a prediction of how likely a website is to rank in search engine results pages, with higher scores meaning a greater likelihood. It is computed from Moz’s own web index, which its Link Explorer tool exposes, by a model trained on how domains actually rank. DA is probably the most widely quoted third-party domain metric, and like all of them it is a vendor’s estimate, not a number Google uses.

What goes into it

Moz does not publish the formula. It describes the inputs and method in general terms:

• Link data from Moz’s index, chiefly the number of distinct linking root domains (referring domains, see backlinks) and the total number of links, along with signals of the quality of those linking domains.
• A machine-learning model. Since Domain Authority 2.0, released in March 2019, the score comes from a neural network trained on how domains rank in Google’s results, which replaced the earlier linear model. Moz said the 2019 version also incorporated its Spam Score and patterns of link manipulation to resist inflated profiles.
• Scaling to 1–100. The model’s output is mapped onto a 1–100 scale on which, by Moz’s account, it is much easier to move from 20 to 30 than from 70 to 80, the behaviour of a logarithmic scale (see ranks and scores).

Page Authority (PA) is the page-level counterpart, predicting how well a single page will rank.

How to read it

• It is comparative. Moz positions DA as a way to compare sites, particularly competitors in the same niche, not as an absolute measure. A DA of 40 is strong for a local bakery and weak for a national newspaper.
• It moves when the index moves. Because the score is calibrated against the whole index, a domain’s DA can change when Moz’s crawl grows or its model is retrained, even if the domain’s own links did not change. Compare scores taken at the same time.
• Small differences are noise. One or two points rarely mean anything, especially at the low end where most domains sit.
• It is not Google’s. Google does not use Domain Authority. A higher DA correlates with better rankings because both depend on links, not because one causes the other.

Relation to the graph measures

DA is, roughly, a learned function of in-degree and of the strength of the linking domains, which is the information PageRank and harmonic centrality use as well. Where it differs:

• The graph. Moz’s index is its own crawl, with its own coverage and freshness, and its own choices about which links count (see web graph).
• The target. DA is fitted to predict rankings, so it can absorb any link feature that predicts them, while PageRank and harmonic centrality are fixed definitions.
• Spam handling. DA explicitly tries to discount manipulative patterns; Common Crawl’s open centralities do not filter anything (see link spam).

Using it for domain evaluation

DA is a reasonable first filter, and a poor final judge:

1. Look at the linking domains Moz lists, not only the score. A DA built on a few strong, relevant domains is worth more than the same DA built on many weak ones.
2. Cross-check with other sources. Compare DA with Domain Rating, Trust Flow and Common Crawl’s positions (see reading domain metrics). When they disagree strongly, find out why before trusting any of them.
3. Watch for inflated profiles. A high DA on a domain with no traffic, a short history and links mostly from unrelated sites is a classic sign of a manufactured link profile, which Google may already ignore.

GoDaddy’s auction inventory, which this encyclopedia’s metric audit examines, does not include Moz metrics, so the audit cannot test DA directly. The same questions apply to it as to the metrics it does include: how much of the score comes from links that carry information about this particular domain?

References

• Moz. What is Domain Authority? moz.com/learn/seo/domain-authority.
• Moz Blog (2019). Domain Authority 2.0 announcement, March 2019.
• Moz. Link Explorer. moz.com/link-explorer.

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