Justoneoverlength

Justoneoverlength is a term used in typesetting and digital typography to describe a controlled overflow policy for line length. It refers to permitting a line to extend beyond the computed maximum line width by exactly one character before wrapping to the next line. The idea is to reduce the frequency of hyphenation and produce more even right edges in cases where content would otherwise produce awkward line breaks.

Origin and usage: The concept emerged in discussions of responsive and justified text, where perfect justification can cause rivers of white space or excessive hyphenation. By allowing a single-character overflow, layouts can maintain a more regular rhythm across lines, particularly in narrow columns or variable fonts.

Implementation: In practice, justoneoverlength is an informal guideline rather than a formal CSS property. It can be realized by configuring the layout engine to tolerate one extra character of content beyond the nominal line length before wrapping, or by adjusting overflow and word-break rules to permit minimal overflow in certain conditions. Designers must balance the improvement in line evenness against potential overflow into adjacent elements or the viewport.

Relation to related concepts: It is related to tolerance in line breaking, overfull boxes in TeX terminology, and to techniques such as hyphenation control, justification, and last-resort overflow handling in responsive design.