Viewer

Viewer is a term with two broad meanings. In everyday language, a viewer is a person who watches something, such as a film, broadcast, or performance. In computing, a viewer refers to a software application that presents content to a user without providing editing tools.

Software viewers include image viewers for photos, PDF viewers for documents, and video players for multimedia. Additional specialized viewers display scientific or technical data, such as medical image viewers (DICOM viewers), GIS map viewers, or CAD and 3D model viewers. Many modern applications bundle viewing capabilities with basic navigation features like zoom, pan, rotate, and page or frame navigation.

Key considerations for viewers are format support, rendering quality, performance, and accessibility. Viewers are typically read-only to prevent unintended modifications, distinguishing them from editors or authoring tools. Some viewers offer lightweight annotation, markup, or commenting, which can border on editing capabilities depending on the context.

In practice, viewers are used in personal consumption (photos and videos), professional workflows (document review, medical imaging, engineering), and on the web, where browsers provide built-in viewing for images, documents, and media. The term also appears in broadcasting as a reference to audience size, or to people who watch content.

See also: media player, document viewer, image viewer, PDF viewer, editor.