LANGID

LANGID stands for language identifier, a 16-bit value used by Windows and related APIs to designate a language and its locale for user interfaces and resources. It encodes two pieces of information: a primary language ID in the high byte and a sublanguage ID in the low byte. LANGIDs can be composed with the MAKELANGID macro by supplying a primary language and a sublanguage. They provide a compact way to refer to a language variant; for example, English (United States) is 0x0409, French (France) is 0x040C, Spanish (Spain) 0x040A, and German (Germany) 0x0407.

LANGID is commonly used by Windows functions such as GetUserDefaultLangID, GetSystemDefaultLangID, SetThreadLocale, and GetLocaleInfo to select resources, fonts, and formatting appropriate for the user’s language. It is distinct from and not the same as an LCID (locale identifier), which is a broader 32-bit value that also encodes sort order and cultural conventions; LCIDs historically combined language, region, and additional rules.

Windows resources, such as satellite DLLs and string tables, are organized by language IDs. At runtime, the system attempts to load resources that match the thread or user LANGID and may fall back to a neutral language if an exact match is unavailable. This mechanism supports multilingual user interfaces without requiring separate code paths for every language.

Background and scope: LANGID values derive from a combination of ISO language codes for the primary language, augmented by Windows-specific sublanguage identifiers. They remain in use for backward compatibility in modern Windows APIs and libraries, providing a stable, compact means of language identification in software localization.