Is there some sort of unique per user identifier that we can use as creators that cant change or will likely not change? For example if i wanted to see if a player was on a whitelist for supporter perks?
Most worlds I’ve seen use string loading (URL) or a hardcoded VRCPlayerApi’s public displayName attribute for display names (identifiers which may change).
Dynamically some worlds have DisBridge integration for managing world features (e.g. whitelists or supporter rewards) based on e.g. Patreon subscriptions linked via a Discord account (if not utilizing the in-app Creator Economy as an alternative). This is a self-service for users, without requiring changes and world updates from the world author even if a supporter’s VRChat account (user ID) changes.
The display name (non-static) can be different from the username (static) which is used to login to VRChat, and that username information is not exposed publicly. I’m not aware of any method of accessing the (static) user ID (e.g. usr_67676767-6767-6767-6767-676767676767) from Udon.