Super Property

A super property is a value registered once in the SDK and then attached automatically to every later event from that device, without being passed on each call.

The SDK keeps it in browser storage, so it survives reloads and new sessions on the same device until it is unregistered or cleared by a reset on logout. The name comes from Mixpanel; Amplitude and Segment have no field with exactly this behaviour, so a value called a super property in one tool may be plain event context in another. It is not a user property: a super property is device-scoped client state that applies only to events sent from that point on, while a user property lives on the person's profile. The failure mode is registering something that changes often, such as the current page or an experiment variant, because the stale value then rides along on unrelated events and quietly corrupts breakdowns.