nonprintable

Nonprintable describes characters that do not have a visible glyph when text is rendered. In computing and typography, these characters are used to control devices, mark data boundaries, or affect layout, rather than to display a symbol.

Common examples are ASCII control codes such as NUL (null), BEL (bell), BS (backspace), HT (horizontal tab), LF (line feed), and ESC (escape). In Unicode, many of these are categorized as C0 and C1 control characters (U+0000–U+001F and U+007F–U+009F).

Other nonprintable or invisible characters include zero-width spaces and zero-width joiners (U+200B, U+200C, U+200D), the word joiner (U+2060), and various formatting marks. These characters may influence text direction, word breaking, or rendering behavior without producing a visible glyph.

Representations in text can be shown by escape sequences or numeric codes in programming languages (for example, \n, \t, or \x0A) or by Unicode notation in editors. Data storage and transmission rely on the code points to convey information even when nothing is visibly drawn.

Handling nonprintable characters is important for data cleaning, search, accessibility, and security. They can complicate indexing, sorting, or display and may be exploited if not properly sanitized or filtered.

See also: printable characters, whitespace, control character, escape sequence, Unicode.