The short answer
Yes. Rebuilt or re-downloaded automatically when needed.
What is it?
Video wallpapers and screen savers (Aerials) that macOS downloads when you choose them in Wallpaper or Screen Saver settings, stored in /Library/Application Support/com.apple.idleassetsd/Customer. Each video is large, so the folder can reach several GB if you have tried many.
What happens if you delete it?
macOS downloads an aerial again whenever you select it. If the one you currently use is removed, it is downloaded again in the background.
How to remove it properly
First choose a still wallpaper or a different screen saver in System Settings › Wallpaper, then move the video files to the Trash in Finder (Go › Go to Folder…). This is a system-wide folder, so an administrator password is needed.
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 macOS aerial wallpaper videos?
Yes. Rebuilt or re-downloaded automatically when needed. macOS downloads an aerial again whenever you select it. If the one you currently use is removed, it is downloaded again in the background.
Will Video wallpapers (Aerials) come back after I delete it?
Yes. macOS downloads an aerial again whenever you select it. If the one you currently use is removed, it is downloaded again in the background.
How do I remove Video wallpapers (Aerials) properly?
First choose a still wallpaper or a different screen saver in System Settings › Wallpaper, then move the video files to the Trash in Finder (Go › Go to Folder…). This is a system-wide folder, so an administrator password is needed.