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Remy Reference/interface/auth.getCurrentVisitorId
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auth.getCurrentVisitorId

The stable anonymous visitor id for the current browser, or null before the session resolves.
auth.getCurrentVisitorId() string | null

Returns a stable id for the current browser, even when nobody is signed in, or null before the session has resolved. It's the anonymous counterpart to a user id: key realtime channels on it for signed-out visitors, so user:null doesn't collapse every anonymous client onto one shared channel. Once a visitor signs in, switch to their user id.

Key a realtime channel for a signed-out visitor
const visitorId = auth.getCurrentVisitorId();
const channel = auth.currentUser
  ? `user:${auth.currentUser.id}`
  : `visitor:${visitorId}`;