lurking

In Internet culture, a lurker is typically a member of an online community who observes, but does not participate by posting. The exact definition depends on context. Lurkers make up a large proportion of all users in online communities. Lurking allows users to learn the conventions of an online community before they participate, improving their socialization when they eventually "de-lurk". However, a lack of social contact while lurking sometimes causes loneliness or apathy among lurkers.
Lurkers are referred to using many names, including browsers, read-only participants, non-public participants, legitimate peripheral participants, vicarious learners, or sleepers.

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