About tethered caching

Learn how to cache certain downloads on your Mac to speed up downloads for connected iOS devices.

This article is intended for users setting up a large number of iOS devices, including school or business administrators. 

macOS Sierra 10.12.4 and later includes the ability to speed up certain types of downloads for iOS devices. When you download cacheable content from the Internet for an iPhone, iPad, or iPod touch that's connected to your Mac, a copy of the download is stored on your Mac. The next time a connected iOS device tries to download the same content, it automatically gets the data directly from your Mac over USB instead downloading it from the Internet again.

Tethered caching is different from the caching service provided by macOS Server, which can be set up for more specific control and doesn’t require clients to connect over USB.

You can’t use both tethered caching and macOS Server’s caching service at the same time.  If you’re already running tethered caching and you install macOS Server, tethered caching will automatically stop.

Requirements for tethered caching

  • A Mac with macOS Sierra 10.12.4 or later, and either iTunes 12.6 or later, or Xcode 8.3 or later. The Mac should be connected to the network via Ethernet. If you use tethered caching, your Mac won’t go to sleep. If your Mac is portable, plug in the power adaptor.
  • An iPhone, iPad, or iPod touch with iOS 10.3 or later.

If you want to connect multiple iOS devices to your Mac simultaneously, you’ll also need a USB hub.

Set up tethered caching

  1. Sign into your Mac as an admin user.
  2. Plug in your ethernet cable and make sure you’re using the ethernet connection to access the Internet.
  3. Open Terminal and enter this command to start the tethered caching service:
    sudo tethered-caching
  4. Connect your iOS devices to your Mac over USB.
  5. On the device, start downloading cacheable content, like a software update. When your content download is complete, you can safely disconnect your device. 
  6. Repeat step 5 for all devices. If you use a USB hub, you can make these change simultaneously. When you start the download, they will get the data directly from your Mac over USB.

Learn more

For more information on the tethered-caching(8) command, launch Terminal on a Mac with macOS Sierra 10.12.4 or later, and run this command:

man tethered-caching

Published Date: 2017-03-27