Windows Universal apps target multiple types of devices via a single codebase. Please specify with other tags if you refer to Windows 8.1 or Windows 10.
You can build an app for Windows and Windows Phone/Mobile at the same time, and share code, user controls, styles, strings and other assets between them. This reduces the expense associated with building and maintaining an app for each type of device.
If you already have a desktop app, you can easily add support for a mobile app. Similarly, if you start by creating a mobile app, you can easily add support for a desktop app.
Please note that since the release of Windows 10, the universal apps for that platform are called Universal Windows Platform (UWP) apps. Therefore please use suitable tags additonally:
- windows-8.1 and/or windows-8.1-universal if your question refer only to Windows 8.1 platform,
- windows-10 and/or windows-10-universal if your question refer only to Windows 10 platform,
- lack of additional tags means that your question is relevant to both platforms.
For some more help regarding:
- Windows 8.1 please take a look at Build apps that target Windows and Windows Phone 8.1,
- Windows 10 please take a look at How-to guides for Windows 10 apps.
Use this tag for any UWP questions - whether building Windows Store Apps, UWP APIs in Win32 applications.
