Microsoft was one of the first companies to implement Unicode in their products. Windows NT was the first operating system that used "wide characters" in system calls. Using the UCS-2 encoding scheme at first, it was upgraded to UTF-16 starting with Windows 2000, allowing a representation of additional planes with surrogate pairs. Nevertheless, Microsoft failed to support UTF-8 until 2017. In Windows 11 some system files are required to use UTF-8.