A viewer is an application used to view, but not edit, the contents of a file that cannot be rendered by a web browser.
Modern web browsers are capable of viewing and playing most types of files without requiring the use of an external viewer. However, there was a time when separate applications were commonly used to play audio and video files and view word processing, PDF, and other types of documents. There are also still times when a viewer is needed to view the contents of a file that isn't hosted in such a way that viewing within the browser is possible.
Applications used to view files which can not be rendered within the browser are referred to as viewers. The most commonly used viewers included:
- Image viewers: While browsers can render images, they may also be downloaded for closer inspection, and a number of image viewing applications are available that are capable of viewing a wide variety of common image formats.
- Media players: Media players applications vary depending on the operating system of the computer playing the media and the format of the media. While most videos stream within web browsers today, in the past it was not unusual for videos on the web to stream by launching a desktop application such as Windows Media Player.
- Plain text document viewers: Plain text files can be rendered within the browser, or downloaded and viewed by many different plain text viewers. Most computers are equipped with a plain text editor that is included with the operating system.
- PDF file viewers: Adobe Acrobat is the most widely used PDF viewer, but there are many alternatives also available for viewing PDF files.
- Specialized and proprietary format viewers: Viewers are available for specialized files such as engineering drawings, as well as proprietary file formats such as Microsoft Office documents and presentations.
Today, most file types can be viewed within the browser itself, or by using web-based file viewing applications. Viewers, and the applications that were used to create the files being viewed are differentiated by the fact that viewers are only designed to view, and not edit, the contents of the file. For example, image viewers can be used to view an image, but are not designed to edit the image.
Frequently Asked Questions
Why are viewers not used as frequently as they were in the past?
Browser developers have made it their goal to make browsing the web increasingly easy to do. One aspect of making the web easy-to-use is to minimize the number of external applications necessary for a full web browsing experience. By adding the ability to stream media and view additional file types directly into the web browser, the number of applications the average web user will need to use is decreased, and web browsing is made a little easier.
Do I have to pay for a viewer for a proprietary file format?
Most common proprietary file types, such as .docx used by Microsoft Word, can be viewed by a free viewer, and most newer computers are powered by an operating system with a built-in viewer. However, there are exceptions. Rich and complex file formats may only be viewable by a specific application, or may offer limited rendering in a separate viewer. Software developers who have chosen to offer a free viewer typically do so out of a desire to encourage broader adoption of the file type.