WYSIWYG (/ˈwɪziwɪɡ/ WIZ-ee-wig) is an acronym for "What You See Is What You Get". In computing, a WYSIWYG editor is a system in which content (text and graphics) displayed onscreen during editing appears in a form closely corresponding to its appearance when printed or displayed as a finished product, which might be a printed document, web page, or slide presentation.

WYSIWYG implies a user interface that allows the user to view something very similar to the end result while the document is being created. In general WYSIWYG implies the ability to directly manipulate the layout of a document without having to type or remember names of layout commands. The actual meaning depends on the user's perspective, e.g.

In presentation programs, compound documents and web pages, WYSIWYG means the display precisely represents the appearance of the page displayed to the end-user, but does not necessarily reflect how the page will be printed unless the printer is specifically matched to the editing program, as it was with the Xerox Star and early versions of the Apple Macintosh.
In word processing and desktop publishing applications, WYSIWYG means that the display simulates the appearance and represents the effect of fonts and line breaks on the final pagination using a specific printer configuration, so that, for example, a citation on page 1 of a 500-page document can accurately refer to a reference three hundred pages later.
WYSIWYG also describes ways to manipulate 3D models in stereo-chemistry, computer- aided design, and 3D computer graphics.

The program on the left uses a WYSIWYG editor to produce a Lorem Ipsum document. The program on the right contains LaTeX code, which when compiled will produce a document that will look very similar to the document on the left. Compilation of formatting code is not a WYSIWYG process.

Modern software does a good job of optimizing the screen display for a particular type of output. For example, a word processor is optimized for output to a typical printer. The software often emulates the resolution of the printer in order to get as close as possible to WYSIWYG. However, that is not the main attraction of WYSIWYG, which is the ability of the user to be able to visualize what he or she is producing.

In many situations, the subtle differences between what the user sees and what the user gets are unimportant. In fact, applications may offer multiple WYSIWYG modes with different levels of "realism", including

A composition mode, in which the user sees something somewhat similar to the end result, but with additional information useful while composing, such as section breaks and non-printing characters, and uses a layout that is more conducive to composing than to layout.
A layout mode, in which the user sees something very similar to the end result, but with some additional information useful in ensuring that elements are properly aligned and spaced, such as margin lines.
A preview mode, in which the application attempts to present a representation that is as close to the final result as possible.