ActivityPub actors are generally one of the ActivityStreams Actor Types, but they don't have to be. For example, a Profile object might be used as an actor, or a type from an ActivityStreams extension. Actors are retrieved like any other Object in ActivityPub. Like other ActivityStreams objects, actors have an id, which is a URI. When entered directly into a user interface (for example on a login form), it is desirable to support simplified naming.

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