Roblox has started an early preview of Scoped User IDs, a privacy change that gives players a unique identifier for each experience instead of exposing one global identifier everywhere. The goal is to make it harder to connect a player's activity across unrelated games.
The first rollout is designed to minimize disruption. Existing players in games they have already visited keep their current Global User ID, while new players entering a game for the first time can receive a Scoped User ID. Roblox says most games will not need code or DataStore migrations immediately.