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[[File:Wikipedia App snapped to Windows 8 desktop.png|thumb|Left: A traditional desktop app without contents; it is showing 60 [[Widget (GUI)|graphical widgets]], and a thick border.<br/>Right: Metro-style app; entirely composed of contents]]
'''Universal Windows Platform''' ('''UWP''') '''apps'''<ref>{{citation|title=Microsoft is trying to change Windows software forever — here's why it'll be a tough fight|first=Matt|last=Weinberger|date=March 17, 2016|url=http://www.businessinsider.com/microsoft-universal-windows-platform-explained|access-date=June 27, 2016}}</ref> (formerly '''Windows Store apps''', '''Metro-style apps''' and '''Modern apps''')<ref name=Harrel>{{citation|title=Metro, Modern, Now Universal? Microsoft Can't Make Up Its Mind!|first=William|last=Harrel|date=April 10, 2015|work=Digital Trends|url=http://www.digitaltrends.com/computing/microsoft-universal-apps/|access-date=June 27, 2016}}</ref> are [[Application software|applications]] that can be used across all compatible [[Microsoft Windows]] devices, including personal computers (PCs), tablets, smartphones, [[Xbox One]], [[Microsoft HoloLens]], and [[Internet of Things]]. TheseWhich are primarily purchased and downloaded via the [[Microsoft Store (digital)|Microsoft Store]].<ref>{{citation|title=Microsoft's Windows app strategy comes under fire: 'The most aggressive move Microsoft has ever made'|first=Matt|last=Weinberger|date=March 4, 2016|work=Business Insider|url=http://www.businessinsider.com/epic-ceo-tim-sweeney-slams-windows-10-2016-3|access-date=June 27, 2016}}</ref>
==Nomenclature==
Starting with [[Windows 10]], Windows initially used "Windows app" to refer to a UWP app. Any app installed from the [[Microsoft Store (digital)|Microsoft Store]] (formerly Windows Store) was initially "Trusted Windows Store app"<ref>[[Cortana (software)|Cortana]]. ''[[Windows 10 1511|Windows 10 version 1511]]''. [[Microsoft]] (2015).</ref> and later "Trusted Microsoft Store apps."<ref>[[Cortana (software)|Cortana]]. ''[[Windows 10 1803|Windows 10 version 1803]]''. [[Microsoft]] (2018).</ref> Other [[computer program]]s running on a desktop computer are "desktop apps." Starting with [[Windows 10 1903]], Windows indiscriminately refers to all of them as "Apps."
The terms "[[Universal Windows Platform]]" (or "UWP") and "UWP app", only appear on Microsoft documentation for its developers.<ref>{{Cite web |url=https://docs.microsoft.com/en-us/windows/uwp/get-started/universal-application-platform-guide |title=What's a Universal Windows Platform (UWP) app? |website=Docs |publisher=[[Microsoft]] |date=7 May 2018}}</ref> Microsoft started to retrospectively use "[[Windows Runtime]] app" to refer to the precursors of UWP app, for which there was no unambiguous name before.<ref>{{Cite web |url=https://docs.microsoft.com/en-us/previous-versions/windows/desktop/apps/dn726537(v=win.10) |title=How to develop a Windows Runtime app |website=Docs |publisher=[[Microsoft]] |date=15 May 2017}}</ref>
== In Windows 8.x ==
Windows software first became available under the name "[[Metro (design language)|Metro]]-style apps" when the Windows Store opened in 2012 and was marketed with [[Windows 8]].<ref name=Harrel/><ref>{{citation|title=Microsoft's Metro apps rechristened with a new, sixth name: Windows apps|first=Jared|last=Newman|work=PCWorld|date=March 26, 2015|url=http://www.pcworld.com/article/2902220/microsofts-metro-apps-rechristened-with-a-new-sixth-name-windows-apps.html|access-date=June 27, 2016}}</ref>
===Look and feel===
In Windows 8.x, Metro-style apps do not run in a [[window (computing)|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 at first. Menus are located in the "[[Windows shell#Charms|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.<ref name="Infoworld-Win81u">{{Cite web |url=http://www.infoworld.com/article/2606675/microsoft-windows/147162-What-s-new-in-the-Windows-8.1-Update.html#slide6 |title=What's new in Windows 8.1 Update |work=[[InfoWorld]] |publisher=[[IDG]] |date=8 April 2014 |first=Woody |last=Leonhart }}</ref>
In response to criticism from customers, in [[Windows 8.1]], a title bar is presentadded but hidden unless users move the mouse cursor to the top of the screen. The "hamburger" menu button on their title bar gives access to the charms.<ref name="Infoworld-Win81u" />
===Distribution and licensing===
For most users, the only point of entry for Metro-style apps is [[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 such as Google and Mozilla Foundation 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.<ref>{{Cite web |url=http://www.zdnet.com/googles-latest-chrome-release-tries-to-replace-the-windows-8-desktop-7000025190 |title=Google's latest Chrome release tries to replace the Windows 8 desktop |work=[[ZDNet]] |publisher=[[CBS Interactive]] |date=15 January 2014 |first=Ed |last=Bott |quote=Under Microsoft’s rules, Metro-style browsers are able to sidestep requirements that apply to all other apps, including the mandate to be distributed through the Windows Store}}</ref><ref>{{cite web|last=Branscombe|first=Mary|title=Windows 8 browsers: the only Metro apps to get desktop power|url=http://www.techradar.com/news/software/operating-systems/windows-8-browsers-the-only-metro-apps-to-get-desktop-power-1073930|work=TechRadar|publisher=Future Publishing|access-date=17 January 2014|date=27 March 2012}}</ref>
Metro-style apps are the only third-party apps that run on [[Windows RT]]. Traditional third-party apps do not run on this operating system.
===Multiple copies===
=== Multitasking ===
In Windows 10, most UWP apps, even those designed for Windows 8.x, are run in floating windows, and users use the Windows taskbar and [[Task View (Windows)|Task View]] to switch between both UWP apps and desktop apps. Windows 10 also introduced "Continuum" or "Tablet Mode". This mode is by default disabled on desktop computers and enabled on tablet computers, but desktop users can switch it on or off manually. When the Tablet Mode is off, apps may have resizable windows and visible title bars. When the Tablet Mode is enabled, resizable apps use the windowing system similar to that of Metro-style apps on Windows 8.x in that they are forced to either occupy the whole screen or be snapped to one side.<ref>{{cite web|last1=Seifert|first1=Dan|title=The nine most important updates in Windows 10|url=https://www.theverge.com/2015/7/29/9060177/microsoft-windows-10-update-changes-browser-start-menu-cortana-xbox#list-item-5|website=[[The Verge]]|publisher=[[Vox Media]]|date=29 July 2015}}</ref><ref>{{Cite web|url = https://www.theverge.com/2015/7/28/9045331/microsoft-windows-10-review|title = Windows 10 review|date = 28 July 2015|website = [[The Verge]]|publisher = [[Vox Media]]|last = Warren|first = Tom}}</ref><ref>{{Cite web|url = http://www.zdnet.com/article/windows-10-a-new-beginning/|title = Windows 10: A new beginning|date = 28 July 2015|website = [[ZDNet]]|publisher = [[CBS Interactive]]|last = Bott|first = Ed}}</ref>
UWP apps in Windows 10 can open in multiple windows. Microsoft Edge, Calculator, and Photos are examples of apps that allow this. Windows 10 v1803 (released in May 2018) added true multi-instancing capabilities, so that multiple independent copies of a UWP app can run.<ref name="multi-instancing" />
=== Licensing and distribution ===
UWP apps can be downloaded from [[Windows Store]] or [[Sideloading|sideloaded]] (using the app installer application from the Microsoft store). The sideloading requirements were reduced significantly from Windows 8.x to 10, but the app must still be signed by a trusted [[digital certificate]] that chains to a [[root certificate]].<ref>{{cite AV media |last1=Sheehan |first1=John |first2=Peyman |last2=Zanjani |date=30 March 2016 |title=Project Centennial: Bringing Existing Desktop Applications to the Universal Windows Platform |medium=Video |url=https://channel9.msdn.com/Events/Build/2016/B829 |access-date=3 April 2016 |minutes=8:50 |___location=San Francisco |publisher=Microsoft Corporation |archive-date=29 January 2018 |archive-url=https://web.archive.org/web/20180129101429/https://channel9.msdn.com/Events/Build/2016/B829 |url-status=dead }}</ref>
==Lifecycle==
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