Editing Multilingual User Interface (section)

=== Language Preferences ===
A language selection is stored by the system for the system (shared by all users and maybe used as default for a new user) and for each user. These selections can be modified by the user via the system Control Panel but cannot be modified by an application. 

These preferences control the language that the OS uses for UI elements. Applications can also use these preferences, and via MUI-enabled system functions (such as LoadString) the use is automatic and transparent (requires no MUI-specific code to use). But use of these preferences is optional and customizable. An application can be designed to ignore the language preferences. Or it may use them in ways other than that provided by MUI-enabled system functions. 

An application can use MUI functions<ref>{{Cite web |last=Karl-Bridge-Microsoft |title=Multilingual User Interface Functions - Win32 apps |url=https://docs.microsoft.com/en-us/windows/win32/intl/multilingual-user-interface-functions |access-date=2022-07-10 |website=docs.microsoft.com |language=en-us}}</ref> to read language preferences -- that default to the user selection [assumed] and are a list of languages in preference order. These preferences are provided at the system, user, process and thread levels [assumed that changing at a higher level modifies the preferences for lower levels]. 

An application can modify these language preference lists (via SetThreadPreferredUILanguages and other functions) in order to influence the behavior of MUI. For example: 
<syntaxhighlight lang="c">
LPCWSTR languageIdSpec = L"en-US\0";
ULONG langCount = 1;
if (!SetThreadPreferredUILanguages(MUI_LANGUAGE_NAME, languageIdSpec, &langCount))
    MessageBoxW(NULL, L"Unable to set thread preferred UI language.", NULL, MB_ICONERROR);
</syntaxhighlight>