The Windows Phone Silverlight 8.1 app model gives Windows Phone 8 developers access to some of the newest features available in Windows Phone Store apps without significantly modifying existing Windows Phone 8 code. Windows Phone 8 apps are fully supported and run exactly the same on Windows Phone 8.1 devices. If you have an existing Windows Phone 8 app and aren’t looking to add new features, you don’t need to modify your app. If you’re just starting out developing for Windows Phone, or if you’re interested in targeting the PC platform in addition to Windows Phone, you might want to start with a Windows Phone Store app. This app model gives you access to all of the new features, and you can target phone and PC with a single Visual Studio solution. For more information about choosing the best platform for your objectives, see .

 

Silverlight 8.1 apps run only on Windows Phone 8.1 devices. Windows Phone 8 devices cannot install or run Silverlight 8.1 apps. However, Windows Phone 8.1 is a free software update that is supported for all existing Windows Phone 8 devices.

 

You can publish a Silverlight 8.1 or Windows Phone Store app alongside an existing Windows Phone 7.8 and Windows Phone 8 version of your app in the Windows Phone Store. If you choose to upgrade your app, you can continue to sell and update earlier versions.

 

For a high-level list of the features of Windows Phone 8.1 that can be accessed from Silverlight 8.1, see .

 

There is a small set of features available in Windows Phone 8 apps for which there are no equivalents in Windows Phone Store apps. Silverlight 8.1 apps can still use these features. If your app requires one of these features you should either maintain your Windows Phone 8 app or upgrade your app to Silverlight 8.1.

 

Clipboard APIs
Lock screen background provider
Ringtone provider
Alarms and reminders
Lens apps
Lock screen background provider
Generating bitmaps for Live Tiles in a Background Task using managed code	Generating bitmaps in a Background Task using native code is supported.

 

For a list of Windows Phone 8 features that are known to behave differently in Silverlight 8.1 apps, see .

 

The tools included in the Windows Phone SDK automate the upgrade of your app from Windows Phone 8 to Silverlight 8.1. This is a one-way process. After you have upgraded, the tools can’t convert your solution back to Windows Phone 8, so be sure to back up your project. For instructions on upgrading your app, see .