Updates and downloads

What is mobileassetd?

mobileassetd downloads system assets for macOS. Apple publishes no man page for it. Kilobat sees it, and its helper, download models, voices, fonts and dictionaries.

Process: mobileassetdAlso seen as: com.apple.MobileAsset.DownloadService.BuiltinMade by AppleApplies to: macOS 14 Sonoma and later. Apple Intelligence downloads need macOS 15.1 or later on a supported Mac. Checked on macOS 27.2.Checked: 1 November 2026

Short answer

Part of macOS, not documented by Apple. Kilobat sees it download system assets such as Apple Intelligence models, voices, fonts and dictionaries.

Block with care

Blocking it stops downloads of models, voices and other assets that macOS features need. To stop the biggest download, turn off Apple Intelligence.

Path
/usr/libexec/mobileassetd
launchd label
com.apple.mobileassetd
Signing identifier
com.apple.mobileassetd com.apple.MobileAsset.DownloadService.Builtin

What it is

Apple publishes no man page or documentation for mobileassetd. The program is /usr/libexec/mobileassetd, signed by Apple. launchd starts it as com.apple.mobileassetd.

A helper named com.apple.MobileAsset.DownloadService.Builtin does downloads for it. In nettop, its name is cut to 15 characters.

Kilobat's list of system downloads says that it gets Apple Intelligence and Siri models, voices, fonts and dictionaries. This is what Kilobat observes, not what Apple documents.

Why it uses the network

  • Apple Intelligence models. Apple says that the on-device models download after you turn on Apple Intelligence, and that the download time varies.
  • Voices, fonts and dictionaries. Kilobat's list of system downloads names these assets too. Apple doesn't document when they download.
  • New models after an update. Apple says that Apple Intelligence storage can grow for a time after a software update, while new models download.

How much is normal

Downloads after a macOS update, or after you turn on a feature, are usual. Apple Intelligence models can be several gigabytes.

Apple recommends Wi-Fi and power for the Apple Intelligence download.

When nothing new is needed, it is quiet for days.

When it uses a lot, and why

  • You turn on Apple Intelligence. The on-device models download. This is the largest download it makes.
  • Right after a macOS update. Apple says that new models can download for a time after a software update.
  • A new voice or language. Adding a voice, a dictation language or a dictionary downloads that asset. Kilobat sees these under this service.

Is it safe to block?

Block with care

Blocking it stops downloads of models, voices and other assets that macOS features need. To stop the biggest download, turn off Apple Intelligence.

What breaks if you block it

  • Apple Intelligence can't finish setting up, and new models after an update don't arrive.
  • New voices, languages and dictionaries can't download.
  • Apple doesn't document every asset it handles, so other features that need a download may fail too.

Blocking means a firewall rule that refuses its connections. Don’t quit or disable a macOS process to save data: macOS starts it again, and other features depend on it.

Reduce its use

  1. Do macOS updates on your usual network. The asset downloads follow them.

  2. If you don't use Apple Intelligence, turn it off in System Settings › Apple Intelligence & Siri. Apple says that the on-device models are then removed.

  3. Add voices and languages only when you are on your usual network.

  4. Don't quit mobileassetd in Activity Monitor. macOS starts it again.

See how much it uses

  1. Open Activity Monitor from Applications › Utilities. Click Network.

  2. Type mobileassetd in the search field. The Sent Bytes and Rcvd Bytes columns show what it moved since it started.

  3. In Terminal, watch only this process. Press d to show the change per second, and q to quit.

    nettop -p 'mobileassetd' -P

With Kilobat

  1. In the Kilobat app list, search for mobileassetd. Its row shows the live rate and what it moved today.

  2. In Connections, click the ⓘ button on one of its rows. The popover shows this page’s short answer, without going online.

  3. In Terminal, ask the same question. Add --json for scripts and agents.

    kilobat explain 'mobileassetd'

  4. Show its traffic over one day.

    kilobat bandwidth 'mobileassetd' day

  5. Through MCP, an AI agent asks explain_connection with the process name. It gets the same facts.

The live view and the explanations are free. History in the app needs Kilobat Pro. Blocking needs Pro and the network filter: see the network filter, Protection and the hotspot data saver.

What isn’t documented

Apple publishes no man page and no support article for mobileassetd. Which assets it downloads, and when, is not documented.

This page describes what Kilobat and the macOS tools show, and what Apple says about Apple Intelligence downloads.

Questions

Why does Apple not document mobileassetd?

Apple publishes man pages for some daemons only. This page describes what Kilobat and the macOS tools show.

Can I stop Apple Intelligence downloads?

Turn Apple Intelligence off. Apple says that the on-device models are then removed from the Mac.

Sources

Checked on 1 November 2026.