Domain Authority isn't a static metric. It's a comparative score from Moz that ranks your site against all other domains in their index. If your DA dropped, three main causes are in play: competitors outpaced you on link acquisition, you lost backlinks, or Moz recalculated their algorithm. The most common scenario is competitive movement. When sites in your niche or industry build more high-quality links than you do in a given period, their scores rise and yours falls relatively. This happens frequently after major content campaigns, PR pushes, or when a competitor publishes linkable assets like studies or tools. You might have done nothing wrong—you just didn't gain ground as fast as the field around you. Actual link loss is the second driver. Run a backlink audit in Ahrefs, Semrush, or Moz itself to check for lost referring domains. Common culprits include site migrations where old links broke, directories or aggregators that pruned listings, or content removals on sites that linked to you. A sudden drop of 10-15 DA often correlates with losing a handful of strong referring domains. Moz also updates its DA calculation periodically—sometimes monthly, sometimes after index refreshes. These updates can shift scores across the board, especially if Moz changed how it weighs link relevance, spam signals, or domain age. Check Moz's blog or the date of the last index update when you notice movement. At Ottawa SEO, we tell clients not to obsess over DA alone. It's a useful benchmark, but Google doesn't use it for ranking. Focus instead on whether organic traffic and rankings held steady or grew. If those dropped too, then yes—diagnose link loss, disavow toxic links if needed, and build replacement links through content, digital PR, or partnerships. If traffic is fine and only DA moved, it's often just the competitive landscape shifting. Keep building quality links at a steady pace, and DA typically recovers within one or two Moz index cycles.