Freeing up space · What's Using Space (Storage Inspector)
Why won't Storage Studio move or clean some of the big items it shows?
Short answer: Some data, like system areas, active mail or an app's live databases, must stay where the system expects it, so it's shown but not offered. Small items aren't worth moving, and in-use ones get Move when closed.
Because moving or clearing them wouldn't be safe. Some data — system areas, active mail, or an app's live databases — needs to stay exactly where the system or the app expects it, so Storage Studio shows it for information but doesn't offer to act on it.
Other items aren't offered because they're small enough that moving them isn't worth it, or because an app is using them right now (those get Move when closed instead).
If you think something should be movable, check the Moving folders FAQ for what can and can't be relocated.