Can I upload user segments using User IDs, and how does User ID tracking work?

Yes, you can manage and track users using User IDs. Here's how:

Uploading Segments with User IDs:

You can upload a client segment using a CSV file that contains UserIDs. For this to work correctly, please ensure:

1. The UserIDs in your CSV file are already registered within your project. Any UserIDs not previously registered will be skipped during the import.
2. The CSV file size is less than 100 MB.
3. The User IDs in the file must be existing User ID values associated with users in your app. (Note: A User ID can be a custom identifier you assign, or it defaults to the device's Hardware ID (HWID) if not customized).

Tracking Customers with User IDs:

User ID is a unique identifier that helps you maintain consistent user data across multiple devices. Here’s how it facilitates tracking:

• Cross-Device Consistency: Link multiple devices (each with its own HWID) to a single User ID, ensuring messages reach the user on any active device.
• User Explorer: Search for specific users by their User ID (as well as HWID or push token) to view their data, devices, and message history.
• Customer Journeys: User IDs are primarily used to track users through cross-channel Customer Journeys and trigger communications based on their actions.
• Event Association: Events can be recorded and linked to a User ID.
• User-Device Association: To effectively use User IDs for targeting, you must associate the User ID with a registered device (HWID) using the setUserId (or registerUser) SDK method in your application.
• Segment Export: Exported segment data includes the User ID, linking devices to users.
• API for Message Logs: You can track notifications sent to a specific User ID using the getMessageLog API.

Important Note: A User (identified by UserID) is dependent on their associated Devices (HWIDs). If a user's last associated device is removed or linked to another user, the UserID will be automatically deleted.