Cross-device tracking helps you understand how users interact with your product across different devices. For example, a user might browse on their phone during lunch break, continue on their work laptop, and complete a purchase on their tablet at home. Without cross-device tracking, these would look like 3 different users.

The key to cross-device tracking is having users identify themselves, usually by logging in. When a user logs in on any device, their actions can be connected to their unique user ID. This helps create a complete picture of their journey, regardless of which device they're using.

Understanding cross-device behavior helps improve user experience. For instance, you might discover that users often start tasks on mobile but prefer to complete them on desktop. This insight could help you design better mobile experiences or add features like "continue on desktop" options.