User properties are uploaded to from sources. Sources are email servers, chat messengers or integrations via API.

Users’ data are usually stored in several sources. To determine which source has priority in recording users’ properties set up the order of the sources in Administration → Manage sources.

User data from the first (highest) source in the list will be imported first. If some field in the user properties is not populated from the higher source and finds necessary data in the lower source in the list, the data will be imported from the lower source.

Thus to record users’ properties via API, you should put API integration created for this first in the list.

This order does not influence the uploading and processing of emails and chats messages.