Domain Authority

Domain Authority is Moz's 1 to 100 score predicting how well a domain ranks in search. Moz builds it from their own link index and trains it against observed rankings, so it is a prediction about Google rather than a number from Google.

Two properties surprise people, and both come from the same design:

• It is logarithmic. Moving from 20 to 30 is far easier than moving from 70 to 80, so a flat chart in the seventies is not a stalled site.
• It is relative. Moz normalizes against the whole index, so a domain can lose a point without losing a link, because other sites gained. This is why Domain Authority and Ahrefs' Domain Rating move on different days.

What Domduck records

Nothing. Domduck holds no Moz data and does not publish a Domain Authority figure.

Substituting a different vendor's number would be worse than leaving the column out. OpenPageRank is free and it is not Domain Authority. A page that answers "DA" with a rebadged score is answering a question the reader did not ask.

There is a second reason this matters here. Moz caps historic Domain Authority at one year, which is a published limit on the exact thing that makes the metric useful: the trend. If you need a longer series, you need something that started recording earlier and never stopped.

Why it matters

Use Domain Authority when your reporting already speaks it, and do not convert it to Domain Rating. The two use different indexes, different crawls and different maths, and the conversion tables on the web are fitted to a handful of sites.

For deciding whether a link is worth having, both scores answer the same question badly. They are third-party guesses at a ranking system neither vendor can see.