Microsoft ‘Project Reunion’ To Unify Win32 And UWP Apps For Windows 10X On Dual-Screen Mobile Computing Devices?

Microsoft published an important document that offers details about ‘Project Reunion’. As the name suggests, the project will involve combining the legacy Win32 Apps with the modern-day UWP (Universal Windows Platform) Apps. The union of the two significantly different platforms should ensure simpler app development and deployment platform for developers who create apps for Windows 10 and most likely the Windows 10X operating system.

With Windows 8, Microsoft attempted a fundamentally different approach to apps. While the legacy Win32 Apps struggled with the modern-day app ecosystem, Microsoft introduced UWP. While UWP was meant to offer streamlined operations, there have been several problems for developers working with two separate platforms for essentially the same purpose. Now Microsoft has finally decided to integrate both the Win32 and UWP ecosystem with ‘Project Reunion’.

Microsoft ‘Project Reunion’ Aims To Unify Win32 and Universal Windows Platform (UWP) Apps:

After the launch and success of touch-based tablets and mobile computing devices, Microsoft attempted to realign the Windows operating system for handheld devices with touchscreens. While the previous Win32 Apps worked well with the keyboard-mouse interface, Microsoft needed apps that were optimized for the web and touch-based interface. Additionally, these apps would be optimized for different screen orientations and use scenarios. Hence the Universal Windows Platform or UWP was created. However, this led to two parallel app development scenarios.

Project Reunion is an attempt to clean up problems created by Microsoft with ‘modern’ UWP apps starting from Windows 8. Users have always treated the legacy Win32 Apps as important for getting work done. Meanwhile, the UWP apps were considered simplified versions for mobile computing devices.

With Project Reunion, Microsoft has essentially rolled up the Win32 API with the UWP API. This will allow developers to add modern features like the Share panel to their desktop apps. Combining the two platforms is important for the unification of two separate development approaches and simplify the app development process.

What Does Microsoft Project Union Offer To App Developers?

The first Project Reunion components are the open-source WinUI 3 and WebView 2. While WinUI 3  is a modern, native UI framework for Windows 10, WebView 2 is a control for integrating web content into an app. Microsoft has now added a clarification to its GitHub page for Project Reunion to explain what the project is and isn’t.

At the onset,  Microsoft has added the C++/WinRTRust/WinRT, and C#/WinRT libraries to Project Union. The public preview of the Rust Windows runtime library was added last month. This would simplify Windows application developers to better utilize Rust. It serves the same purpose as the Windows runtimes for code written in C++ and C#. Microsoft also added MISX-Core, which is essentially a way for developers to distribute applications to Windows PCs via the store or their own third-party mechanism.

Microsoft has clarified that Project Union isn’t a new application model or platform. In other words, there won’t be a ‘new Project Reunion App’ template for Visual Studio, VS Code, or other development environments. Speaking about the same, Microsoft mentioned, “You’ll still have full access to the Windows SDK and associated kits. Over time the features that Project Reunion provides will grow beyond just merging the existing Win32 and UWP models and provide additional functionality for all apps to use.”

Microsoft also clarified that Project Union is not a new packaging or isolation model for applications. Neither is it a new security model for applications. Moreover, Project Union is not meant for developers to run an app in the cloud. Nonetheless, Project Reunion technology will help get an app on modern API families that are cloud-ready.

Alap Naik Desai


A B.Tech Plastics (UDCT) and a Windows enthusiast. Optimizing the OS, exploring software, searching and deploying solutions to strange and weird issues is Alap's main interest.