Domain Authority is a score (on a 100-point scale) developed by Moz that predicts how well a website will rank on search engines. Use Domain Authority when comparing one site to another or tracking the “strength” of your website over time. We calculate this metric by combining all of our other link metrics—linking root domains, number of total links, MozRank, MozTrust, etc. —into a single score. To determine Domain Authority, we employ machine learning against Google's algorithm to best model how search
engine results are generated. Over 40 signals are included in this calculation. This means your website's Domain Authority score will often fluctuate. For this reason, it's best to use Domain Authority as a competitive metric against other sites as opposed to a historic measure of your internal SEO efforts. How is Domain Authority Scored?

We score Domain Authority on a 100-point, logarithmic scale. Thus, it's easier to grow your score from 20 to 30 than it would be to grow from 70 to 80. Domain Authority vs. Page Authority Whereas Domain Authority measures the predictive ranking strength of entire domains or subdomains, Page Authority measures the strength of individual page.

The same is true for metrics such as MozRank and MozTrust. Where can you Find Domain Authority? Domain Authority metrics are incorporated into dozens of SEO and online marketing platforms across the web. You can measure Domain Authority using Open Site Explorer or the MozBar, Moz's free SEO toolbar. Moz incorporates Authority metrics into all Moz Analytics campaigns, as well as the Mozscape API. Read more about how to build an authority site.