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 May 2019 Microsoft reversed course and started recommending using UTF-8 exclusively.