 Locale (computing)

A locale, also called a software locale, identifies a set of language-related and regional conventions used by software. Locale-sensitive services use it to select behavior such as date formatting, number formatting or culturally appropriate text ordering. A locale identifier can specify a language, script, region and further options.^[ref]

An original date example separates meaning from presentation. Let a stored value have year2026, month3 and day4. A day/month/year pattern displays 04/03/2026, while a month/day/year pattern displays 03/04/2026. Both represent the same date under their declared patterns. The bare strings do not carry all the information needed to choose the interpretation without context.

A program can pass the selected locale as a parameter to a formatting service instead of hard-coding every convention. Changing that parameter changes the presentation requested for the operation. It does not change the stored date's year, month and day, infer a user's nationality, or convert the character encoding of every string.^[ref]

The distinction from encoding is especially useful. Two applications can both store text as UTF-8 while choosing different locale-sensitive display forms. Conversely, two different byte encodings can represent the same textual date. A test record should therefore identify the semantic value, locale selection, format options and relevant library/data version separately.

The Common Locale Data & Rules project supplies shared data for such services, and International Components for Unicode provides implementations using locale information. A default locale is a convenience for choosing behavior when the application does not supply an explicit choice; making the choice explicit improves reproducibility of an example.^[ref]