File viewer applications can be split into the following categories:
File Viewer Only applications do not allow the user to edit files.
File Viewer and Converter applications allow viewing data, exporting data in a different file format, and copying information to the clipboard.
File Viewer and Editor applications allow the user to view existing files, modify an existing file's content, or create a new file of a specific type.
The difference in file viewers' functionality initially resulted from how proprietary file formats were licensed. While all file formats can be read freely, some software licenses allow only the licensor to create and modify files. For example, the database software DBASE used a proprietary algorithm for creating .DBF files, but Norton Commander had a built-in viewer for .DBF files. A software application such as Adobe Photoshop, LibreOffice, or Microsoft Word is required to create .PDF files, but Acrobat Reader supports viewing of .PDF files.[2]
A file format must have structural information that allows a file viewer to handle different byte orders, code pages or newline styles. In contrast, media file viewers, such as video player applications, may initially support few, if any, file formats. Media file viewers instead rely on video codecs to play various media, allowing users to expand a media file viewer's capability to read and represent media file data.
Some media editors, such as Audacity, allow users to open most files as "raw data."[3] This has been used by artists to make glitch art.[4]
Some file viewers are filters that translate binary files into plain text (e.g., antiword). However some information may be lost depending on the translating routines.
Image viewers display graphic files on screen. Some viewers, such as IrfanView, can read multiple graphic file formats, while others, such as JPEGview only support a single format. Common image viewer features include thumbnail preview and creation, image zooming and rotation, color balance and gamma correction, resizing, etc.
A web browser is a type of file viewer that renders HTML markup into a human-friendly presentation. Although HTML is stored in plain text files, viewing an HTML file in a browser and in a text editor produces significantly different results. Web browsers may also view multimedia files such as images, videos, preformatted documents, interactive environments, 3D models, augmented reality and virtual reality applets.
