Part of macOS

`mobileassetd`System downloads

○ Leave it

Downloads extra parts of macOS, such as voices and fonts.

What it is

Fetches resources macOS needs on demand, like dictionaries, voices and on-device models.

Why it might be busy

After an update, or when you turn on a feature that needs a download. Usually a few minutes.

If you stop it

macOS starts it again straight away. Leave it.

○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.

From Procession’s guide, in the words the app shows.