Universal Windows Platform apps

Note that UWP is primarily used in Microsoft's developer documentation to specifically refer to the platform itself.

They have no title bar, system menu, window borders or control buttons.

[5] 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.

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.

Metro-style apps, however, are identified by their "tiles" that can show their icon and also other dynamic contents.

For example, one user may run as many copies of programs such as Windows Notepad, Paint or Firefox as long as the system resources can support.

(Some desktop apps, such as Windows Media Player, have extra code that prevents spawning more than one instance.)

When the Tablet Mode is off, apps may have resizable windows and visible title bars.

Windows 10 v1803 (released in May 2018) added true multi-instancing capabilities, so that multiple independent copies of a UWP app can run.

[19] Calling a forbidden API disqualifies the app from appearing on Windows Store.

[20][21][22] UWP apps developed to work on smartphones, personal computers, video game consoles and HoloLens.

[25][26] Universal apps no longer indicate having been written for a specific OS in their manifest; instead, they target one or more device families, e.g. desktop, mobile, console or Internet of Things (IoT).

A universal app may run on both a mobile phone and a tablet and provide a suitable experience.

[31] The Windows Phone 8.x Marketplace allowed users to download APPX files to an SD card and install them manually.

In contrast, sideloading of UWP apps was prohibited on Windows 8.x, unless the user had a developers license or was in a business domain.

They need permission to access hardware devices such as webcams, microphones or their file system which is restricted to user folders, such as My Documents.

Microsoft further moderates these programs and may remove them from the Windows Store if they are discovered to have security or privacy issues.