When you download cacheable content from the Internet on 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 that an iOS device that’s connected to your Mac tries to download the same content, it downloads directly from your Mac through USB. This is called “tethered caching.”
Tethered caching differs from the caching service in macOS Server, which provides more specific control and doesn’t require clients to connect with USB.
In macOS High Sierra, tethered caching is now available as Content Caching, which you can access in System Preferences > Sharing. Learn about Content Caching in macOS High Sierra.
Check requirements for tethered caching
To use tethered caching, here's what you’ll need:
- An iPhone, iPad, or iPod touch with iOS 10.3 or later
- A Mac with macOS Sierra, and either iTunes 12.6 or later, or Xcode 8.3 or later
To connect multiple iOS devices to your Mac simultaneously, you’ll also need a USB hub.
Set up tethered caching
- If your Mac is a notebook, plug in the power adapter.
- Log in to your Mac as an admin user.
- Connect your Mac to the Internet with an Ethernet cable.
- In Finder, click Applications.
- From the Utilities folder, open Terminal.
- Type or paste this command in Terminal, then press Return to start the tethered caching service:
- Connect an iOS device to your Mac through USB.
- On the iOS device, download cacheable content, like a software update.* After the download completes, safely disconnect your device.
- Repeat steps 7 and 8 for all devices. If you use a USB hub, you can download cacheable content on all your devices simultaneously. When you start the download, your devices get the data directly from your Mac with an Ethernet cable.
For more information about the
tethered-caching(8) command, open Terminal on a Mac with macOS 10.12.4 or later. Then run the
man tethered-caching command.
* Instead of manually starting the download in step 8, you could use a mobile device management (MDM) solution to install the cached software on your connected iOS devices. When iOS devices are connected to a Mac through USB, they share the network and receive MDM commands.