Windows Template Library (WTL) is a library designed to aid in the development of Windows applications and user interface components. It offers a collection of open-source tools and templates written in C++, enabling customization of various elements within an app's interface, such as frames, objects, dialog boxes, sheets, and properties. Originally created for internal use by a Microsoft employee, WTL's utility led to its release for public use. It serves as an add-on for Visual Studio and an SDK for crafting Win32 apps.

To utilize Windows Template Library (WTL), installation of Visual Studio for Windows is necessary, along with a foundational understanding of the Win32 API and its core concepts. While official Microsoft resources for WTL are lacking, a robust community provides support for users looking to harness its capabilities effectively.