The goal of this post is to share how we, at the Browser Company, have made it possible to use Swift to build a modern Windows application. There is no UI framework for Windows written in Swift, and Windows itself is written in C++ – so that may leave you wondering, “how can I build my app on Windows”? Modern Windows applications use WinRT, a technology built on top of COM, which can interop really well with Swift, as we presented in our previous post. To be able to build idiomatic UI for Windows in Swift, we have built a language projection tool which creates idiomatic Swift language bindings for WinRT, and today we are open sourcing it at https://github.com/thebrowsercompany/swift-winrt. Swift/Winrt is based on Microsoft’s code generators for C++ (github.com/microsoft/cppwinrt) and C# (github.com/microsoft/cswinrt), and thus is written in C++.