User Property

A user property is an attribute stored on a person's profile, such as plan, city or signup date, and used to segment and break down their behavior.

It is set with an identify call or a profile update, and it lives on the profile rather than on any single event. Whether a report uses today's value or the value at the time of the action differs by tool: some stamp the property onto each event at ingestion, others read the latest profile value at query time, and only the first can answer a question about the past correctly. The line against an event property is simple: an event property describes the action, a user property describes the person. The failure mode is storing something that changes often, such as last order status, as a user property; the profile keeps only the newest value, so history is quietly rewritten to look like today.