Multilingual User Interface

Multilingual User Interface
Other namesMUI
DeveloperMicrosoft
Initial releaseFebruary 17, 2000
Written inC++
Included withMicrosoft Windows, Windows Phone
PredecessorStatic localization
LicenseProprietary
WebsiteMicrosoft Learn - Multilingual User Interface

The Multilingual User Interface (MUI) is a dynamic localization framework used in Microsoft Windows, Windows Phone, and compatible programs; it allows language files to be modular and separate from application logic. It is designed to simplify the development and deployment of localized software.

MUI has a number of advantages compared to traditional static localization. Software that uses MUI can do the following:

  • Store language resources in dedicated files instead of hardcoding them into program binaries, making it possible to update localizations and code dynamically without recompilation.
  • Automatically select a language from Windows' language preferences, instead of asking the user at runtime.
  • Use the Win32 API to load resources from MUI language files.

The MUI framework, API, and its localization files (called Language Packs, or LPs) were introduced in Windows 2000; these were significantly expanded on with Windows Vista, which allowed developers to use MUI in their software. Language Interface Packs (LIPs) were added in Windows 7 to supplement Language Packs. LIPs were replaced by Local Experience Packs (LXPs) in Windows 10 build 1809.