Universal Windows Platform (UWP) apps (formerly named Windows Store apps, Metro-style apps and Modern apps) are applications that can be used across all compatible Microsoft Windows devices. They are primarily purchased and downloaded via the Microsoft Store, Microsoft's digital application storefront. UWP stopped adding new features in October 2021, but toolchain updates continue to be made.

Starting with Windows 10, Microsoft initially used the term "Windows app" to describe Universal Windows Platform (UWP) apps. These were applications that could be installed from the Microsoft Store, previously known as the Windows Store. Initially, these apps were called "Trusted Windows Store apps," and later they were referred to as "Trusted Microsoft Store apps." Traditional programs designed to run on desktop computers were referred to as "desktop apps."

With the release of the Windows 10, version 1903, there was a shift in the terminology. Microsoft began using the term "Apps" to refer to both UWP apps and desktop apps indiscriminately. This change aimed to unify the naming convention for all types of applications.

Note that UWP is primarily used in Microsoft's developer documentation to specifically refer to the platform itself. Microsoft also introduced the term "Windows Runtime app" retrospectively to describe the precursors of UWP apps, as there was previously no clear and unambiguous name for them.

UWP apps first became available under the name "Metro-style apps" in 2012 and were marketed with Windows 8.

In Windows 8.x, Metro-style apps do not run in a window. Instead, they either occupy the entire screen or are snapped to one side, in which case they occupy the entire height of the screen but only part of its width. They have no title bar, system menu, window borders or control buttons. Command interfaces like scroll bars are usually hidden on start. Menus are located in the "settings charm." Metro-style apps use the UI controls of Windows 8.x and typically follow Windows 8.x UI guidelines, such as horizontal scrolling and the inclusion of edge-UIs, like the app bar.

In response to criticism from customers a title bar was added in Windows 8.1, but was hidden unless users move the mouse cursor to the top of the screen. However, the Hamburger button on the title bar gives access to the charms.

For most users, the only point of entry for Metro-style apps is the Windows Store. Enterprises operating a Windows domain infrastructure may enter into a contract with Microsoft that allows them to sideload their line-of-business Metro-style apps, circumventing Windows Store. Also, major web browser vendors are selectively exempted from this rule, they are allowed to circumvent Microsoft guidelines and Windows Store and run a Metro-style version of themselves if the user chooses to make their product the default web browser.