Because the Microsoft Store servers are offline, you cannot simply double-click a XAP file to install it. You must use Sideloading.
The Windows Phone UI ("Metro") was a radical design departure that influenced iOS and Android. The design language is preserved in these .xap files. windows phone xap archive
The urgency for XAP archiving stems from a specific event: The Windows Phone Store Shutdown. Because the Microsoft Store servers are offline, you
If you have a physical device running Windows Phone 8 or 8.1, you can sideload apps without complex tools. Deploy via PC: