Domain Authority is a comparative metric from Moz that scores your site 1-100 based on how it ranks against all other domains in their index. When your DA drops, it typically means other sites in the ecosystem gained backlinks faster than you did, shifting your relative position downward. DA recalculates regularly as Moz refreshes its link graph, so drops after index updates are common even if you did nothing wrong. The most common causes are lost backlinks—sites that linked to you removed the link, went offline, or added nofollow tags—and stagnant link acquisition while competitors kept building. Check your backlink profile in Ahrefs or Semrush for recent lost links. A sudden drop of 50+ referring domains often correlates with DA declines. Toxic link removals can also trigger drops if those links were previously inflating your score, though cleaning spam usually improves rankings even if DA dips temporarily. Moz also updates its algorithm periodically, which can shift scores across the board. A 3-5 point drop during an update isn't unusual and doesn't necessarily reflect your actual search performance. DA is a third-party metric—Google doesn't use it. We've seen clients with DA 28 outrank DA 45 competitors because they had better topical authority and user signals. At Ottawa SEO, we track DA as one signal among many but prioritize actual Google rankings and organic traffic. If your DA dropped but your rankings held or improved, ignore it. If both dropped, audit your backlink losses, check for manual actions in Search Console, and compare your link growth rate to the top 5 competitors in your niche. Often the fix is simply resuming consistent link building—guest posts, digital PR, or resource page placements—at a pace that matches or exceeds your competitive set. Focus on links from relevant, authoritative sources rather than chasing DA as a vanity metric.