There are three types of ID described below.
Global ID: a Ripple assigned user ID unique to each participant and is global throughout all studies and the registry. This is a locked field that is unable to be changed through the Registry. However, this can be updated/customized by importing participants and including the new preferred global ID with the following fields constant as before: new Global ID, First Name, Last Name, and Birthdate. Ripple uses these variables to match and update the participant's global ID
Custom ID: a user defined ID to track a participant at the study level. Another way to think of the Custom ID is this is the participant's study ID. Users can use the same ID between studies, but not the same ID within a study. A participant's Custom ID is the identifier that is shown on a participants event details on the Ripple calendar and in the calendar subscription.
Family ID: a user defined ID to track participants in families/groups/cohorts on a global level. When participants have the same Family ID they will show up in the "Family" section of each others participant profiles and you will be able to see the studies they are in, their name, gender, and current age.