A remarketing window is the predefined period of time after a user's interaction with a website, mobile app, or advertisement during which they remain eligible to receive personalized remarketing ads. The length of the remarketing window depends on factors such as the product type, the typical buying cycle, and user behavior. A well-optimized remarketing window ensures that ads are shown while they are still relevant, improving conversion rates, reducing wasted ad spend, and preventing campaigns from targeting users who have already converted or are no longer likely to engage.