Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun viewer

2 senses of viewer

Sense 1
spectator, witness, viewer, watcher, looker -- (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")
       => perceiver, percipient, observer, beholder -- (a person who becomes aware (of things or events) through the senses)

Sense 2
viewer -- (an optical device for viewing photographic transparencies)
       => optical device -- (a device for producing or controlling light)