A version of this page is also available for

Windows Embedded CE 6.0 R3


This function maps a character string to a wide-character (Unicode) string.

The character string mapped by this function is not necessarily from a multibyte character set.


int MultiByteToWideChar(
  UINT CodePage,
  DWORD dwFlags,
  LPCSTR lpMultiByteStr,
  int cbMultiByte,
  LPWSTR lpWideCharStr,
  int cchWideChar


  • CodePage
    [in] Code page to be used to perform the conversion. This parameter can be given the value of any code page that is installed or available in the system.

    The following table shows possible values.

    Value Description


    ANSI code page


    Not supported


    OEM code page


    Not supported


    Not supported


    UTF-7 code page


    UTF-8 code page

  • dwFlags
    [in] Specifies whether to translate to precomposed or composite wide characters if a composite form exists, whether to use glyph characters in place of control characters, and how to deal with invalid characters.

    You can specify a combination of the flag constants shown in the following table.

    Value Description


    Always use composite characters โ€” that is, characters in which a base character and a nonspacing character have different character values.

    Cannot be used with MB_PRECOMPOSED.


    If the function encounters an invalid input character, it fails and GetLastError returns ERROR_NO_UNICODE_TRANSLATION.


    Always use precomposed characters โ€” that is, characters in which a base character and a nonspacing character have a single character value.

    This is the default translation option. Cannot be used with MB_COMPOSITE.


    Use glyph characters instead of control characters.

    A composite character consists of a base character and a nonspacing character, each having different character values.

    A precomposed character has a single character value for a base/nonspacing character combination.

    In the character รจ, the e is the base character and the accent grave mark is the nonspacing character.

    The function's default behavior is to translate to the precomposed form. If a precomposed form does not exist, the function attempts to translate to a composite form.

    The flags MB_PRECOMPOSED and MB_COMPOSITE are mutually exclusive. The MB_USEGLYPHCHARS flag and the MB_ERR_INVALID_CHARS can be set regardless of the state of the other flags.

  • lpMultiByteStr
    [in] Pointer to the character string to be converted.
  • cbMultiByte
    [in] Size, in bytes, of the string pointed to by the lpMultiByteStr parameter. If this value is โ€“1, the string is assumed to be null terminated and the length is calculated automatically.
  • lpWideCharStr
    [out] Pointer to a buffer that receives the translated string.
  • cchWideChar
    [in] Size, in wide characters, of the buffer pointed to by the lpWideCharStr parameter.

    If this value is zero, the function returns the required buffer size, in wide characters, and makes no use of the lpWideCharStr buffer.

Return Value

Number of wide characters written to the buffer pointed to by lpWideCharStr if the function succeeds and cchWideChar is nonzero.

The required size, in wide characters, for a buffer that can receive the translated string if the function succeeds and cchWideChar is zero.


The return value includes the NULL termination character.

Zero indicates failure. To get extended error information, call GetLastError. Possible values for GetLastError include the following:



If lpMultiByteStr and lpWideCharStr pointers are the same, the function fails, and GetLastError returns the value ERROR_INVALID_PARAMETER. The function fails if MB_ERR_INVALID_CHARS is set and it encounters an invalid character in the source string.

An invalid character is one that would translate to the default character if MB_ERR_INVALID_CHARS was not set, but is not the default character in the source string, or when a lead byte is found in a string and there is no valid trail byte for DBCS strings. When an invalid character is found, and MB_ERR_INVALID_CHARS is set, the function returns 0 and sets GetLastError with the error ERROR_NO_UNICODE_TRANSLATION.


Header winnls.h
Library coredll.lib
Windows Embedded CE Windows CE 1.01 and later
Windows Mobile Windows Mobile Version 5.0 and later

See Also


Unicode Functions

Other Resources