How can I manage push notifications and user-specific data when multiple users share the same device and switch accounts in my app?

When your app supports several user profiles on one device, make sure push notifications and user data always follow the profile that is currently active. In Pushwoosh a device (identified by its HWID) is linked to exactly one User ID at a time.

1. When a user logs in or switches profiles:

• Set the User ID. After login, call the SDK's setUserId method with that profile's identifier. The device is transferred to the new user, keeping its device tags.

  // iOS (Swift)
  Pushwoosh.sharedInstance().setUserId("USER_ID_FOR_CURRENT_PROFILE")
  
  // Android (Java/Kotlin)
  Pushwoosh.getInstance().setUserId("USER_ID_FOR_CURRENT_PROFILE");
  
  // Web SDK
  Pushwoosh.push(function (api) { api.registerUser("USER_ID_FOR_CURRENT_PROFILE"); });
  

• Refresh user tags. Right after setUserId, call setTags with the values that belong to the new profile, so segmentation and personalization are correct for the active user.

  Pushwoosh.sharedInstance().setTags(["user_level": "premium", "interests": "sports"])
  

2. When a user logs out:

• Call setUserId again with a default value - the documented approach is to reset it to the device's original HWID, which is what an anonymous device uses. Do not pass an empty string: it is not a valid identifier and does not reliably detach the profile.

  // Reset to the anonymous default (device HWID)
  Pushwoosh.sharedInstance().setUserId(Pushwoosh.sharedInstance().getHWID())
  

Important considerations:

• Timing: call setUserId after the SDK is initialized and the device is registered for push notifications.
• One active User ID per device: calling setUserId with a new value overwrites the previous association. A device cannot belong to two User IDs at once.
• Device limit per user: a User ID can hold up to 20 devices. When a 21st is added, Pushwoosh removes one existing device (the oldest inactive non-email device) instead of rejecting the registration.
• User vs device tags: user-specific tags follow the User ID and change with the profile; device-specific tags stay with the HWID and are unaffected by User ID changes.
• Transition side effect: when a device moves between users, device tags are preserved while user-specific tags are re-read from the new user's profile (or reset to defaults if the user is new).

See Users (User IDs).