onecolumn

Onecolumn is a page layout in which content runs in a single vertical column from top to bottom, with the column typically spanning the available width of the page or viewport. It contrasts with multi-column layouts, which divide the content area into two or more columns. One-column layouts are common for books, reports, legal documents, and other content where uninterrupted prose and a straightforward reading path are desirable. They are also used in electronic documents and on devices with narrow screens, where a single column can simplify navigation and typography.

In typesetting and digital publishing, one-column mode can be selected or enforced to disable column breaks. In LaTeX, the documentclass option onecolumn or the command \onecolumn switches to a single column, with \twocolumn reversing the change. Some document classes and publishing frameworks provide explicit onecolumn settings to ensure compatibility across formats. In web design and word processing, a single-column layout is achieved by using a content container that occupies the full width and by avoiding column-count or column-setup features. Responsive designs may start in one-column mode on small screens and transition to multi-column layouts as space allows.

Advantages include simpler typography, consistent left alignment, and room for wide images or equations. Disadvantages include less efficient use of horizontal space on wide pages and longer line lengths if margins are small, which can affect readability.