Domain Authority is a search engine ranking score developed by Moz that runs from 1 to 100, with higher scores corresponding to greater likelihood of ranking well. It's calculated using dozens of factors including linking root domains, total number of links, and MozRank, then compiled into a single logarithmic score. Sites like Wikipedia sit in the high 90s, while most new sites start in the single digits. DA is purely predictive and comparative. Google doesn't use it in their algorithm at all. It exists to give SEOs and link builders a quick way to evaluate whether a backlink or potential partner site carries weight. When we're prospecting link targets at Ottawa SEO, we generally look for DA 30+ for client campaigns, though context matters more than the raw number. A niche-relevant DA 25 site often delivers more value than an irrelevant DA 50. The score is logarithmic, meaning it's much easier to grow from 20 to 30 than from 70 to 80. You improve DA by earning high-quality backlinks from diverse referring domains, not by manipulating the metric itself. Buying links from low-quality DA 40 sites won't help rankings and can trigger penalties, even if the number looks decent. Competitors to DA include Ahrefs' Domain Rating (DR) and Semrush's Authority Score. All three correlate reasonably well with ranking ability but use different link indexes and calculation methods, so scores vary between tools. A site might show DA 35, DR 42, and Authority Score 28 for the same domain. Use DA as a directional filter, not gospel. We've seen DA 15 sites outrank DA 60 competitors because they had superior on-page relevance, user signals, and topical authority in a narrow niche. Focus on building links that drive referral traffic and editorial credibility first. DA improvement follows naturally when you're earning links the right way, not chasing a vanity metric that Google ignores.