Domain Authority isn't one universal metric—it's a proprietary score each SEO tool calculates differently. Moz's Domain Authority (DA) is the original, scored 0-100, but Ahrefs calls theirs Domain Rating (DR), Semrush uses Authority Score (AS), and Majestic has Trust Flow and Citation Flow. All measure roughly the same thing: how strong a site's backlink profile is compared to others. The fastest free method is installing MozBar, Moz's Chrome extension. Visit any site and the toolbar shows its DA instantly. The free version limits you to a few queries daily. For bulk checks or deeper analysis, you need paid access to Moz Pro, Ahrefs, or Semrush. Ahrefs is generally considered most accurate for backlink data in 2025, which makes DR particularly reliable for link prospecting. To check DA manually in any tool: paste the domain into the search bar, run the analysis, and you'll see the authority score alongside metrics like referring domains, total backlinks, and spam score. When we evaluate link opportunities at Ottawa SEO, we cross-reference DA with topical relevance and traffic—a DA 45 site in your niche with real traffic beats a DA 60 zombie domain every time. Important context: DA is comparative, not absolute. A DA 30 might be excellent in a local Ottawa niche but weak in competitive SaaS. The score updates as Moz's index refreshes, so fluctuations of ±3 points mean nothing. Also, DA measures link equity potential, not actual rankings—plenty of DA 20 sites outrank DA 50 competitors because they nail content and user intent. Watch out for artificially inflated DA from PBNs or link schemes. Check the backlink profile quality, not just the number. If a site has DA 40 but 90% of links come from irrelevant foreign directories, that authority is hollow. We always verify referring domain diversity and anchor text ratios before considering any site for outreach or link acquisition.