Domain Authority was created by Moz, the Seattle-based SEO software company, back in 2004. Rand Fishkin and his team at SEOmoz (the company's original name) built DA as a predictive ranking score on a 1-100 scale. The goal was to give SEOs a reliable proxy metric after Google stopped updating its public PageRank toolbar and made their internal ranking signals increasingly opaque. Moz calculates DA using a machine learning model that evaluates linking root domains, total links, MozRank, MozTrust, and dozens of other factors. The score predicts how likely a domain is to rank in search results compared to competitors. It's logarithmic, so moving from 20 to 30 is easier than jumping from 70 to 80. Moz updates the entire index periodically, which means your DA can fluctuate even if you haven't changed anything, simply because the competitive landscape shifted. DA is not a Google ranking factor. Google has repeatedly clarified they don't use Moz's metric in their algorithm. It's an independent measurement created by a third party. That said, DA correlates reasonably well with ranking potential because it's built on similar principles, link equity and authority signals, that Google does care about. At Ottawa SEO, we track DA across our 500+ domain portfolio mostly for internal benchmarking and quick health checks. A domain at DA 35 typically has more link equity than one at DA 18, so it's a useful shorthand when prioritizing where to build content or acquire backlinks. But we never optimize for DA directly. We optimize for real Google rankings, user signals, and revenue. If DA rises as a byproduct, great. If it stalls while organic traffic climbs, that's fine too. Other companies have since launched competing metrics: Ahrefs Domain Rating, Semrush Authority Score, Majestic Trust Flow. All attempt the same thing, quantifying domain strength on a standardized scale. None replace actual ranking data, but they're faster to check than running a full SERP analysis. Just remember DA is a correlation tool, not a causation lever.