Applies to: Acoustic Campaign  ·  Mobile  ·  SDK  ·  Mobile User ID

This article explains how the Acoustic SDK generates a Mobile User ID (MUID) during app registration and what happens to the MUID when a user reinstalls the app.

How the MUID is created

1. The SDK uses the Android Device ID or a custom iOS GUID generated by the SDK to create a unique install identity.
2. This identifier, along with other metadata, is included in the registration call to the Acoustic service.
3. The service hashes this information to generate a unique Mobile User ID (MUID).
4. The process ensures the MUID is unique within the Acoustic data layer.

What happens when a user reinstalls the app

If a user deletes and reinstalls the app, the Install ID remains unchanged. As a result, the same MUID is reassigned to that user upon re-registration — preserving continuity of the mobile contact record.

Creating a new MUID for the same install

If the registration payload includes the flag invalidateExistingUser = true, the service creates a new MUID using the same Install ID and permanently deletes the old record. Use this flag with caution, as the previous mobile contact record cannot be recovered after deletion.