preformatting

Preformatting refers to the preservation of whitespace and line breaks in a block of text, preventing the rendering engine from collapsing sequences of spaces or line endings into a single space. It is commonly used for content where exact spacing matters, such as source code, tabular data, ASCII art, poetry, or logs.

In HTML and similar markup languages, preformatted text is delivered with a dedicated element, typically the <pre> tag, which instructs the browser to render the enclosed text with a fixed-width font and to preserve whitespace and line breaks. Such blocks are often paired with code or used for displaying output from programs. The appearance can be further controlled with CSS, including the use of monospace fonts and indentation preservation.

CSS provides explicit control over preformatted text through the white-space property, enabling values such as pre, pre-wrap, and pre-line. These options let designers balance exact line breaks with the need to wrap text for readability, making preformatted blocks adaptable to different screen sizes and devices.

Outside HTML, preformatting is used in word processing, documentation, and data preparation to stage text before final layout. It includes practices like normalizing whitespace in data pipelines, preserving indentation in source snippets, or maintaining alignment in ASCII representations.

Limitations include potential readability issues on small displays, accessibility concerns if the content is not semantically labeled as code or preformatted, and the risk of overusing fixed-width formatting in prose. Proper use typically pairs preformatted blocks with clear semantics and appropriate styling.