Their chat badges, if we've seen a message from them.

Their chat name color, if we've seen a message from them with a valid color set.

Arbitrary per-viewer data - stash gameplay state here, e.g. viewer.Data.Set( "score", 10 ). Lazily created, so viewers with no data cost nothing. This lives only as long as the viewer is in the roster: if they leave (or get pruned) and come back it's a fresh viewer with an empty bag, so keep anything you can't afford to lose in your own game state instead.

Their display name. Falls back to Sandbox.Streamer.Viewer.Username until we've seen a chat message from them.

Whether we've seen this viewer actually chat, or only join.

Whether this viewer is the broadcaster (channel owner).

Whether this viewer is a channel moderator.

Whether this viewer is a subscriber (founders count as subscribers).

Whether this viewer is a VIP.

The viewer's stable numeric platform user id. Unlike Sandbox.Streamer.Viewer.Username this never changes, so it's the key to use when persisting per-viewer state. Null until we've seen them chat, sub, or appear in the chatter list.

The viewer's login name (lowercase). This is the key we track them by in the roster, but a viewer can change it - use Sandbox.Streamer.Viewer.StreamerId as their persistent identity.