"Cross-device tracking" in digital marketing refers to the ability to monitor and analyze user behavior across multiple devices, such as smartphones, tablets, and desktops. This technique allows marketers to create a cohesive understanding of a customer's journey, capturing interactions as they switch between devices. By employing cookies, mobile IDs, and other tracking mechanisms, businesses can deliver more relevant and personalized advertising experiences. Cross-device tracking enhances the effectiveness of marketing campaigns and improves ROI by ensuring that messages reach users consistently, regardless of the device they are using.