> sometimes small, sometimes large And sometimes not reasonably possible at all, because e.g. like all sandboxing approaches I'm aware of, Apple's file sandbox

> sometimes small, sometimes large And sometimes not reasonably possible at all, because e.g. like all sandboxing approaches I'm aware of, Apple's file sandboxing, too, sucks at handling multi-file file formats. (Though to give them credit, they're the only ones who at least have made an attempt at handling those [1], even if that still only covers a rather limited part of that use case.) [1] At least according to the documentation I've found, their sandboxing should be able to handle "related" files that only differ in their file extensions, but a number of existing file formats are easily more complex than that. I think that's still more than what's possible on Android, Windows or Linux, though…