viewer

noun6

1. •
   Someone who views a spectacle; an onlooker or spectator.
2. •
   Someone who watches television.
3. •
   Any optical device used to view photographic slides.
4. •
   A program that displays the contents of a file.

   • This image viewer can display pictures in GIF, PNG and JPG format.
5. •
   (historical) An appointed inspector or examiner
6. •
   (historical) The manager of a colliery, who directs its workings and ventilation.