What is mobileassetd on a Mac, and what is it downloading?
mobileassetd downloads system assets: voices, dictionaries, fonts, language and Apple Intelligence models. It ran as root with 3 MB here. Where the downloads go.
What is mobileassetd?
mobileassetd fetches the parts of macOS that are downloaded on demand instead of shipped with it: Siri and dictation voices, dictionaries, extra fonts, language models, simulator runtimes and Apple Intelligence models. It lives at /usr/libexec/mobileassetd and runs as root; ours used 3 MB and had been running for five hours.
Where do the assets go?
Into /System/Library/AssetsV2. On this Mac that folder was 33 GB, most of it simulator runtimes, with Siri understanding and language data after them; see system Library assets and Siri and speech assets.
Why is mobileassetd busy?
- After a macOS update, which refreshes many assets.
- When you turn on a feature that needs a download: a new language, a voice, Apple Intelligence.
- When an app asks for a font or dictionary for the first time.
See it live
Free Mac's System tab ranks every process by processor use and energy impact, once a second, and marks the ones macOS will not let you quit as protected. See also triald.
Related: apsd and mDNSResponder.
Common questions
What is mobileassetd on a Mac?
The macOS process that downloads on demand assets such as voices, dictionaries, fonts and language models.
Where does mobileassetd store downloads?
In /System/Library/AssetsV2. It was 33 GB on our Mac.
Can I stop mobileassetd downloading?
Turn off the features that need the assets. The process itself is part of macOS.