The short answer
Yes. Rebuilt or re-downloaded automatically when needed.
What is it?
Unity’s Package Manager keeps a global cache of downloaded packages and registry data in ~/Library/Unity/cache, shared by all your projects. It grows as you use more packages and versions. Typically a few hundred MB to several GB.
What happens if you delete it?
Unity downloads the packages a project needs again the next time you open it, so that opening is slower. Your projects are not changed.
How to remove it properly
Quit Unity and Unity Hub, then move the folder to the Trash in Finder (Go › Go to Folder… ~/Library/Unity/cache).
Quit the app that uses it, then move it to the Trash. Empty the Trash when you’re sure.
How MoreRoom helps
MoreRoom recognises this item, shows its real size and when it was last used, and labels it “Safe to remove”. In the free version you can move it to the Trash in one click, with Undo; Pro collects every safe item at once.
Frequently asked questions
Is it safe to delete Unity’s global cache (~/Library/Unity/cache)?
Yes. Rebuilt or re-downloaded automatically when needed. Unity downloads the packages a project needs again the next time you open it, so that opening is slower. Your projects are not changed.
Will Unity caches come back after I delete it?
Yes. Unity downloads the packages a project needs again the next time you open it, so that opening is slower. Your projects are not changed.
How do I remove Unity caches properly?
Quit Unity and Unity Hub, then move the folder to the Trash in Finder (Go › Go to Folder… ~/Library/Unity/cache).