A domain whose registration was allowed to lapse and is now available — or has been re-registered by a new owner. SEO interest comes from the residual backlink profile and historical authority a quality expired domain may retain, used either to relaunch a new site under the existing equity or (more commonly) for "PBN" private-blog-network spam. Google's spam policies explicitly target the latter ("expired domain abuse" was named as a violation in the March 2024 spam update); whole sites built on top of an unrelated expired domain's history have been deindexed. Legitimate uses include reclaiming a former brand domain or recovering content via the Wayback Machine.