Target Disk Mode has long been one of the Mac’s unique capabilities — it allows you to bypass the operating system entirely and access the internal drive directly, as though it were an external drive. This makes it easy to migrate data from one computer to another, perform disk repairs, or retrieve data from a Mac with a damaged operating system.
To activate Target Disk Mode, you hold down the T key immediately after you turn on your Mac, before the Apple logo appears in the center of the screen.
Target Disk Mode has only been available for Macs with Thunderbolt or FireWire (and, for you old-timers, PowerBook SCSI). This has meant that models which only offer USB connections, such as the 2008-2009 MacBook Air and MacBook, don’t offer Target Disk Mode.
That’s been fixed. The MacBook 12″ does not offer Thunderbolt (and, by extension, FireWire), but Target Disk Mode is available over USB. The 2016 MacBook Pro also offers Target Disk Mode over USB, in addition to Thunderbolt and FireWire (though the latter requires two adapters).
Target Disk Mode over USB only works when connected via USB 3, so it can only be used with 2012 and later Macs (despite Apple’s support article erroneously suggesting older models, by stating “any Mac”). Nor can Target Disk Mode be used with Apple’s USB-C charge cable, which is a USB 2 cable when used for data.
So, to use Target Disk Mode over USB, you can use:
- a USB 3 C-to-A cable if connecting to a Mac with USB-A ports (most Macs)
- a USB 3 C-to-C cable if connecting to a Mac with USB-C ports (MacBook 12″, 2016 MacBook Pro)
But if you’ve got a 2016 MacBook Pro and are connecting to a Mac that has a Thunderbolt port (i.e any Mac from 2011 or later, except for the MacBook 12″), it’s easier and potentially faster to use Thunderbolt, using the Thunderbolt 3 to Thunderbolt 2 adapter and a Thunderbolt 2 cable, or, if you’re connecting two 2016 MacBook Pros, a ThunderBolt 3 cable (which can also operate as a USB 3 C-to-C cable).
So, great — we can do something with our Macs that I wish we could have had long ago.
Image of G3 iMac from Wikipedia’s page on Target Disk Mode.