DigitOnly

DigitOnly is a term used in computing to refer to strings or identifiers that contain only decimal digits. It is also the name used by several libraries and utilities designed to work with digit-only strings. In data validation, a digit-only constraint ensures that input contains no letters or symbols other than digits 0 through 9.

Common features of digitonly tooling include validation, generation, and transformation. Validation checks whether a given string matches the digit-only pattern, often implemented with regular expressions such as ^[0-9]+$ in ASCII contexts, or patterns that permit Unicode digits. Generation facilities create fixed-length numeric strings, useful for IDs, codes, or tokens. Normalization capabilities may remove spaces, separators, or groupings (for example, turning 12-34-56 into 123456), while preserving leading zeros if required. Some implementations handle locale-specific digits or full-width digits and provide options to reject strings containing non-digit characters.

Architectures vary, but many digitonly tools expose a small API: isDigitOnly(s) returns true/false; toDigitOnly(s) converts or validates; generate(length) returns a string of digits; and normalize(s, options) applies rules.

Digit-only constraints appear in web forms, databases, and software that requires numeric identifiers, such as account numbers or PINs. The notion is often important when input must be preserve formatting, such as leading zeros, or when non-numeric characters could cause parsing errors.

See also: numeric string, regular expression, unicode digits.