viewer

nouns

a close observer; someone who looks at something (such as an exhibition of some kind)
"the spectators applauded the performance"; "television viewers"; "sky watchers discovered a new star"
looker, spectator, viewer, watcher, witness
is derived from
view
an optical device for viewing photographic transparencies
viewer
is derived from
view
is a type of (narrower)
a device for producing or controlling light
optical device