Domain Authority (DA) is a metric created by Moz to estimate the likelihood of a domain ranking well in Google search results. The 0–100 logarithmic score is calculated based on backlink profile factors including total linking domains, total links, and Moz's analysis of link quality. Despite being a third-party metric (not from Google), DA has become widely adopted across the SEO industry as a quick benchmark for site authority. The critical clarification: Google does not use Domain Authority. Google has its own internal authority signals — historically PageRank and now a complex blend of factors not publicly disclosed. Google has explicitly stated multiple times that DA, DR (Ahrefs Domain Rating), AS (Semrush Authority Score), and similar third-party metrics are not ranking factors. They are estimates of authority, not direct inputs to rankings. Despite not being a Google ranking factor, DA still matters in three practical ways: (1) Benchmarking — comparing your DA to competitors provides directional insight into whether your authority profile is competitive in your market; (2) Link prospecting — DA helps prioritize which sites to pursue backlinks from (higher-DA sites generally provide more valuable links); (3) Industry communication — clients, agencies, and prospects use DA as shorthand for site authority, so understanding it helps with stakeholder conversations. The limitations of DA: (1) It's a global metric, not topic-specific — a site with high DA in cooking has high DA when used to evaluate links to your SEO site, but the topical relevance is missing; (2) It can be manipulated through link spam in the short term (link sellers explicitly target Moz's calculation methodology); (3) It updates on Moz's schedule, not in real-time; (4) It correlates with but doesn't perfectly predict actual ranking performance — many lower-DA sites outrank higher-DA sites in specific verticals or for specific queries. The alternative authority metrics worth tracking: Ahrefs Domain Rating (DR) — uses a similar 0-100 scale with different methodology focused heavily on backlink profile; Semrush Authority Score (AS) — incorporates traffic and engagement signals beyond just backlinks; Majestic Trust Flow (TF) and Citation Flow (CF) — separate trust from quantity, useful for link-quality assessment. Most experienced SEOs use a combination of these metrics rather than relying on any single tool. For Canadian businesses, the practical workflow: track your DA monthly as one of several authority benchmarks; compare to your top 5 organic competitors quarterly; use Moz's Link Explorer (or Ahrefs Site Explorer, Semrush Backlink Analytics) to identify high-DA sites in your niche to pursue for backlinks; and remember that improving DA is an output of doing good SEO, not an input — focus on earning quality backlinks from relevant Canadian sources, and DA improvements follow. The most useful application of DA in Canadian SEO: link prospect filtering. When evaluating potential link sources, filter Ahrefs or Moz data for Canadian sites with DA above your domain's current DA. This narrows the prospect list to authority-building opportunities while avoiding wasted outreach to lower-authority sites that contribute marginal value.