.APPXSYM File Extension
File TypeWindows 8 App Package Symbols File
What is an APPXSYM file?
File format introduced as part of the Windows 8 app packaging system for the Windows Store; contains public symbol information for the app that allows crash reporting details to be sent back to the developer (via the Window's Store developer dashboard) when the app crashes on a user's computer.
APPXSYM files are included within .APPXUPLOAD files when the app is packaged and submitted to the Windows Store. If you choose not to include symbols for crash reporting, you can submit an .APPX file instead, and an APPXSYM file is not used.
NOTE: APPXSYM files are created when you package your app using the Create App Packages wizard in Visual Studio.