Things known as a viewer include:
- For television viewer, see Audience; Audience measurement; Nielsen ratings
- File viewer, a piece of computer software that displays the data stored in a computer file in a human-friendly form
- Image viewer, a computer program that displays a stored graphical image
- Pocket viewer, a model range of Personal Digital Assistants developed by Casio
- ViEWER, a computer program written for the purposes of studying visual perception in a 3-D environment
- A person who is engaged in the paranormal activity of remote viewing