If you are desperately searching for a —hoping to find a fresh, working installation file—you have arrived at the right place. This guide covers the history of the app, where to find the last "new" builds, and how to side load them. The XAP Evolution: From Microsoft to Facebook First, a quick history lesson. The file extension .xap (not to be confused with Silverlight XAP) is the application package for Windows Phone 7, 8, and 8.1. (Windows 10 Mobile later shifted to .appx ).
Nowhere is this more painful than with Facebook. Microsoft officially pulled the plug on the Windows Phone 8.1 and Windows 10 Mobile stores for many legacy devices. The built-in Facebook app errors out; the login screen loops forever. facebook windows phone xap new
By: Windows Phone Legacy Archive