Domain Authority was created by Moz, the Seattle-based SEO software company originally founded as SEOmoz by Rand Fishkin and Gillian Muessig in 2004. Moz developed DA as a predictive ranking score on a 0-100 scale to help SEO practitioners estimate a domain's likelihood of ranking in search results without access to Google's internal metrics. The metric launched publicly with Moz's Link Explorer toolset and has been continuously refined since then, most significantly with the DA 2.0 update in early 2019 that changed the underlying calculation model. DA is calculated using machine learning against Moz's link index, incorporating factors like the number of linking root domains, total link count, and the quality signals of those links. It's completely separate from anything Google uses internally. Google has repeatedly stated they don't use Domain Authority in their algorithm, yet DA became widely adopted because it provided a single number that correlated reasonably well with ranking performance when other factors like content quality and search intent were comparable. The confusion around DA stems from practitioners treating it as if Google cares about it directly. Google doesn't. What Google does care about are the underlying signals that DA attempts to model: authoritative backlinks, editorial links from trusted sources, and overall link profile strength. DA is just Moz's interpretation of those signals. At Ottawa SEO, we reference DA when discussing link targets or evaluating partnership opportunities because it's a common language clients understand, but we're explicit that it's a third-party metric. A DA 45 site isn't automatically better than DA 42; you need to look at topical relevance, traffic, and actual editorial standards. We've seen DA 30 niche sites in Canadian markets outperform DA 60 general directories for link value because Google cares about relevance and trust in context, not a score from Moz's algorithm. Use DA as one reference point among many, never as the sole decision factor for link building.