Get to understand the Universal Windows Platform (UWP) Applications

UWP Apps

The general idea of UWP apps is that they allow developers to build applications that run across PCs, tablets, Xbox, Surface devices, and IoT devices without altering the codebase. UWP is not the first technology that tried to achieve this; however, like most technologies in this area, many of them haven’t become very popular.

UWP apps are designed to run in a secure, sandboxed environment.

You can distribute them through the Microsoft Store or package them as an MSIX file, which can then be hosted on a website or shared publicly for installation.

UWP apps were the first “modern” type of applications, which had access to modern APIs such as touch, notifications, live tiles, and adaptive UI.

Since then, Microsoft has shifted its focus to the Windows App SDK and WinUI (which is also used by Advanced Installer); however, technically, UWP apps are still supported.

UWP apps can be built in managed languages such as C#, VB.NET, C++, and JavaScript. Some examples of popular UWP apps are the Windows Calculator, Microsoft Photos, Microsoft To Do, Xbox App, Weather app, and some other Microsoft apps that come preinstalled on the OS.

UWP Apps Packaging

UWP applications are already packaged in APPX or MSIX formats when built in Visual Studio.

For example, every time you publish a UWP app, this will generate an MSIX package by default, which means that no conversion is needed in this case.

MSIX is Microsoft’s modern packaging format that aims to unify Appx (the format introduced initially and used by modern UWP apps) and legacy installers, commonly referred to as Desktop Apps or Win32 Applications.

If you are wondering why you cannot package a UWP app as an MSI, the reason is simple: the UWP app package itself is the actual installer, and UWP applications require a trusted certificate for installation – just like MSIX. While MSI packages can also be technically signed, the structure is completely different between APPX/MSIX packages and MSI packages.

MSI packages “legacy” installers built on the Windows Installer technology, and function like “databases”. If you ever open an MSI, you will see that, in its raw format, it’s essentially a database that the Windows Installer knows how to read, and each table entry serves a specific purpose and performs specific actions.

MSIX packages are a completely different and more modern technology. Each time you run an MSIX package, the App Installer service is called. If you right-click an MSIX and extract it, you will see that it is actually a “zip” file, which contains all the data, unlike the MSI technology.

Furthermore, all installation details are defined in the AppxManifest.xml, which is present in all the MSIX packages.

You can convert MSI packages to MSIX by using Advanced Installer or the Microsoft MSIX packaging tool. We actually have a step-by-step guide on how easily you can convert an MSI to an MSIX without repackaging it (like other tools require) that you can check if you are interested.

Of course, MSI packages aren’t the only installers that can be converted to MSIX. Basically, all types of installers, like EXE, self-extracting installers, and so on, can be converted, though these scenarios require repackaging.

Conclusion

UWP introduced Microsoft’s vision of apps running securely across devices with a single codebase. While newer frameworks like WinUI and the Windows App SDK have taken center stage, UWP remains supported, and many core Windows apps still rely on it.

MSIX is the modern packaging format that unifies UWP’s Appx model with legacy desktop installers. Unlike MSI, which applies only to Win32 apps, UWP apps are already MSIX‑ready by design. For developers, the path forward is clear: use MSIX for consistent, secure, and future‑proof deployment.