macOS processes

What is mobileassetd on Mac?

mobileassetd downloads system assets for macOS. Apple does not document it. Kilobat sees it download models, voices, fonts and dictionaries.

Process: mobileassetdProcess: com.apple.MobileAsset.DownloadService.BuiltinApplies to: All current macOS versions. Apple Intelligence downloads need macOS 15.1 or later on a supported Mac. Seen on macOS 27.2.Checked: 29 October 2026

Where you see it

  • mobileassetd is in the list in Activity Monitor › Network, in nettop or in Kilobat.
  • A firewall or network monitor asks if mobileassetd can connect.
  • A large download starts after a macOS update, with no app open.

What it is

Apple publishes no man page or documentation for mobileassetd. The program is /usr/libexec/mobileassetd, signed by Apple.

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 on-device models download after a software update, and that the download time varies.
  • Voices, fonts and dictionaries. Kilobat's list of system downloads names these assets too. Apple does not 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.

Is it normal?

Yes. 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.

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.

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

    nettop -p mobileassetd -P

  4. Also look for the helper. In nettop, use its short name.

    nettop -p com.apple.Mobil -P

Reduce or pause it safely

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

  2. If you do not 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. Do not quit mobileassetd in Activity Monitor. It is part of macOS, and other features depend on it.

With Kilobat

  1. Open the Kilobat app list and search for mobileassetd. Its row shows the live rate and the bytes it moved.

  2. Kilobat puts this service in the System downloads group, with one line about what it does. Expand the group to see each service.

  3. With the network filter on, click the service. The panel names the apps that the downloads were for, for example “For Music”.

  4. Without the filter, macOS shows only the service. Then Kilobat cannot say which app a download was for.

  5. In Terminal, see the same live list. Press / and type the name to search.

    kilobat status --watch

  6. Show its traffic over one day. Names match kilobat report --summary.

    kilobat bandwidth mobileassetd day

  7. Through MCP, an AI agent gets the same history with get_app_bandwidth and the name mobileassetd.

  8. The live view is free. History in the app needs Pro. Kilobat records history only while the app runs.

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

Sources checked on 29 October 2026. Man pages are the ones installed with macOS; open one with man <name> in Terminal.