Defined in header <wctype.h>
wint_t towlower( wint_t wc );
(since C95)

Converts the given wide character to lowercase, if possible.


wc - wide character to be converted

Return value

Lowercase version of wc or unmodified wc if no lowercase version is listed in the current C locale.


Only 1:1 character mapping can be performed by this function, e.g. the Greek uppercase letter 'Σ' has two lowercase forms, depending on the position in a word: 'σ' and 'ς'. A call to towlower cannot be used to obtain the correct lowercase form in this case.

ISO 30112 specifies which pairs of Unicode characters are included in this mapping.


#include <stdio.h>
#include <wchar.h>
#include <wctype.h>
#include <locale.h>
int main(void)
    wchar_t wc = L'\u0190'; // Latin capital open E ('Ɛ')
    printf("in the default locale, towlower(%#x) = %#x\n", wc, towlower(wc));
    setlocale(LC_ALL, "en_US.utf8");
    printf("in Unicode locale, towlower(%#x) = %#x\n", wc, towlower(wc));


in the default locale, towlower(0x190) = 0x190
in Unicode locale, towlower(0x190) = 0x25b


  • C11 standard (ISO/IEC 9899:2011):
    • The towlower function (p: 453)
  • C99 standard (ISO/IEC 9899:1999):
    • The towlower function (p: 399)

See also

converts a wide character to uppercase
converts a character to lowercase
C++ documentation for towlower

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