Cloud accounts · Cloud apps on your Mac
How does Box Drive use space on my Mac?
Short answer: Box Drive streams files on demand, so only what you've opened or marked for offline use takes space. Turn off offline use for folders you don't need to reclaim space; your files stay in Box.
Box Drive shows your Box account as a folder in Finder but streams files: they're fetched when you open them, and only what you've opened or marked for offline use takes space on your Mac. Folders you mark to keep offline are kept fully on your Mac, so those are the usual reason Box Drive grows.
To get space back, turn off offline use for folders you don't need offline, using Box Drive's options in Finder's right-click menu. Your files stay in Box.
Box isn't an account type you can add in Storage Studio right now, and macOS doesn't let Storage Studio free another provider's downloads. You can still use the Box Drive folder in transfers as a Local folder account — reading files from it may download them first. See connecting Box.