[Capability usage] The removableStorage capability provides programmatic access to files on removable storage, like USB keys and external hard drives, filtered to the file-type associations declared in the package manifest. For example, if a document-reader app declares a .doc file-type association, it can open .doc files on the removable storage device, but not other types of files. Be careful when declaring this capability, because users may include a variety of info in their removable storage devices, and will expect your app to provide a valid justification for programmatic access to the removable storage for all files of the declared type. Users will expect your app to handle any file associations that you declare. So don't declare file associations that your app cannot handle responsibly. The file picker provides a robust UI mechanism that lets users open files for use with an app. Declare the removableStorage capability only when the scenarios for your app require programmatic access and can't be realized by using the file picker. [Capability scenario] 
Removable Storage