Domain Authority is a proprietary score developed by Moz that ranges from 1 to 100, with higher scores indicating greater likelihood of ranking well in search engines. It's calculated using dozens of signals including linking root domains, total backlinks, MozRank, and MozTrust. Important distinction: DA is not used by Google. It's a third-party metric that attempts to model what Google might consider when evaluating site authority. DA works as a comparative tool rather than an absolute measure. A DA of 40 isn't twice as good as 20, and moving from 70 to 80 is exponentially harder than going from 20 to 30. Established government sites typically score 90+, major news outlets 80-95, while most small business sites sit between 15-35. A brand new domain starts at 1. We use DA at Ottawa SEO as one reference point when evaluating link opportunities, but never in isolation. A niche-relevant site with DA 28 and engaged traffic often delivers more SEO value than an irrelevant DA 65 site. The metric became less reliable after Moz's 2019 DA 2.0 update caused widespread score fluctuations across our 500+ domain portfolio. Competing metrics include Ahrefs Domain Rating (DR) and Semrush Authority Score, each using different calculation methods. DR typically skews higher than DA for the same site. When clients ask about improving their DA, we redirect to what actually matters: earning quality backlinks from relevant sites, producing content that attracts natural links, and fixing technical SEO issues. DA moves slowly. Adding 10-15 quality links might budge a score by 2-3 points over several months. Obsessing over the number misses the point. Focus on building genuine authority through expertise, quality content, and relationships in your industry. The score will follow, and more importantly, so will your actual Google rankings and organic traffic.