High Quality Content by WIKIPEDIA articles! The Windows Template Library (WTL) is a free software, object-oriented C++ template library for Win32 development. WTL was created by Microsoft employee Nenad Stefanovic for internal use and later released as an unsupported add-on to Visual Studio and the Win32 Framework SDK. It was developed primarily as a light-weight alternative to the Microsoft Foundation Classes and builds upon Microsoft`s ATL, another lightweight API widely used to create COM and ActiveX libraries.