How to delete my personal files retained by an app? I'm using Android Excel and Word apps on a non-rooted Galaxy Note 8. Over the past months I've opened a couple of files from external sources (email and SD card), but was shocked to find these files could still be opened after the source was gone.

It appears the files reside "somewhere" in /data/user/0. When I launch the app, it displays a file list including the path. I tried to delete these files and get a prompt saying I don't have permission.

This is crazy! If I ever lost my phone, these sensitive files would be compromised!
Apps store their data (including opened / downloaded / created files, databases, settings, caches etc.) in /data/data/&lt;pkg_name&gt;/ and /sdcard/Android/data/&lt;pkg_name&gt;/. It's not possible to delete files from former location without root access. So what you can do is either clear data of the app, or uninstall/reinstall the app in order to delete all files.