Singleline

Singleline is a term used in computing to describe text or input that occupies a single physical line. The notion contrasts with multiline content, where line breaks create multiple lines. In user interfaces and data entry, singleline mode constrains input to one line and may reject newline characters or automatically compress whitespace. It is commonly used for usernames, passwords, search fields, and other compact inputs. Some editors and templating systems offer a singleline rendering option to display or serialize content on one line, often for compact logs or in-line display.

In regular expressions and related text-processing contexts, singleline mode (also called DOTALL) changes how the dot metacharacter behaves. When enabled, the dot matches every character including newline; when disabled, it matches any character except newline. This behavior is toggled via a flag or inline construct, such as the s modifier in many engines or the (?s) construct. The exact syntax depends on the engine, so developers consult the engine's documentation.

In programming languages, the term singleline can describe string literals that do not span line breaks. Many languages support both single-line and multiline strings or rely on escape sequences to embed newlines within a single string. The concept is particularly relevant in data formats and templates that must fit within a single line, for example, in log records or URL parameters.

Because the meaning of singleline can vary by context, readers should verify the intended usage in the specific tool or language. See also multiline, dot matches newline, and single-line comment in programming languages.