How does an SEO company improve domain authority?
An SEO company cannot raise Domain Authority directly, because it is a score Moz calculates, primarily from its own link data, not a setting on your site. Moz’s explanation of Domain Authority says the score “is designed to reflect the overall strength of your domain’s link profile compared to others”, and that “Domain Authority is not a Google ranking factor and has no effect on the SERPs.” So the work that can move the score is work on your link profile, and even then it moves on Moz’s terms. Content quality matters for how your pages perform in search, and good content can earn links, but the depth of your content is not an input to the score. DA is useful for comparison, and a poor target for a contract.
What the score measures
Moz describes Domain Authority as a score that “ranges from 1 to 100” and predicts how likely a site is to rank compared with competitors. It is calculated from Moz’s link index, with “the quality and quantity of backlinks pointing to your site” weighing heavily.
Two properties of the score matter if anyone promises to move it. First, it is relative. Moz gives the example that “if Facebook.com acquired a billion new links, other site’s DA would drop relative to Facebook’s.” Your score can change without anything changing on your site. Second, it gets harder to raise as it rises: Moz notes that “it’s easier to grow your score from 20 to 30 than it is to grow it from 70 to 80.” A promised jump of ten points means very different things at different starting levels.
The score also moves on Moz’s schedule, since it depends on when Moz’s index picks up new links. Real improvement in your link profile can show up in the score later than it happened.
What the company actually works on
Three kinds of work matter, and only the first acts on the score directly, through the links Moz records. The first is links from relevant, credible sites: sources in your own field that your customers would recognize, rather than unrelated sites chosen because of a high score. The company earns these through useful content, outreach, expert commentary, and recovering mentions that do not yet link to you. Buying links for ranking purposes is listed as link spam in Google’s spam policies, which is a risk no score is worth.
The second is depth on your core subjects. Covering a topic thoroughly, with a main page supported by detailed pages on its subtopics and linked together sensibly, makes the site more useful and gives other sites more reason to cite it.
The third is material worth citing. Original data, clear guides, and tools that solve a real problem attract links on their merits.
How to read a DA promise
A proposal that promises a specific DA number is promising a change in a third-party score that is not a Google ranking factor, that can fall when other sites grow, and that moves on another company’s update schedule. Ask instead what the company will do to your link profile and content, and how it will report it: the linking sites earned, the pages they point to, and the searches and pages where visibility improved. If DA appears in the report at all, treat it as a comparison with competitors measured by the same tool, not as the result you are paying for.