[stavros]

When I had an iPhone (a few months ago), there was no way for apps to see files in the filesystem. I wanted to play some music and I had to copy it over to each of the music player apps separately. Is that not the case any more?

[sussmannbaka]

That’s entirely up to the app developer. Of course apps can see files if they’re developed to do that.

[badc0ffee]

VLC for iOS uses the filesystem. You can add files with Finder (newer macOS), iTunes (older macOS), or the Files app on the phone.

You are correct that each app can only see a specific part of the filesystem, unless the apps are by the same developer and part of an App Group.