As long as you can get your Mac up and running, the fastest way to transfer files from its internal storage is back-to-back Thunderbolt networking, easily set up in Network settings. Problems come when, for any reason, your Mac won’t start up sufficiently to enable that. Then you’re best off trying to put the ailing Mac into Target Disk Mode and connecting it to another Mac to rescue your most critical files, before it goes off to get fixed.

Gone are the days that you could open your Mac up, pop its hard disk out, and use that to recover whatever you could. While you may still be able to do that with Intel Macs without a T2 chip, for almost every other Mac, internal storage is no longer removable, and you’ll need Target Disk Mode.

In these instructions, I’ll refer to the Mac you put into Target Disk Mode as the Target, and the Mac you connect to it as the Host. Steps required differ mainly by the architecture of the Target, whether it’s an Intel or Apple silicon model.

Target Disk Mode on Apple silicon Macs

If an Apple silicon Mac can still start up in Recovery, or Fallback Recovery, you should be able to put it into Target Disk Mode from there. With recent firmware and macOS, this is straightforward. Start with the Host up and running, then connect it to the Target using a Thunderbolt 3 or 4 cable; if you don’t have one of those, Apple states this also works with a regular USB or USB-C cable too, although transfers should be significantly slower.

If the Target is a notebook and automatically tries to start up when you open it up, shut it down. Next start the Target up with the Power button held until the display shows Loading Startup Options, then release it. This takes you to the Startup Options screen. Select the Options icon, then click Continue underneath it. Once the main Recovery mode window has loaded, open the Utilities menu and select the Share Disk command. Work through the sequence to select the disk until it offers you a button to turn sharing on. Click on that and authenticate to unlock that volume on the Target, then click on the button a second time to enable sharing.

On the Host, open the Network location in the Finder’s sidebar, and you should find it has already connected to the Target as the guest user, and you can copy whatever you need to rescue. You can also copy files to the Target, although in the circumstances you’re unlikely to want to. When you’re ready to disconnect, eject the Target from the Host and, on the Target, click on the button to stop sharing. Before shutting a Target notebook down, disconnect the Thunderbolt cable, or it will probably start up again.

Using a Thunderbolt 3 cable to connect Target and Host, transfer speeds are surprisingly fast, typically 1-1.5 GB/s. However, as the connection works using SMB, there is overhead when transferring many smaller files. It should still be feasible for you to recover most of your important files over a reasonably short period.

Target Disk Mode on Intel T2 Macs

There are now two ways to enter Target Disk Mode on an Intel Mac with a T2 chip: if the Mac is already up and running (and not near-dead at all), you can opt for this in System Settings > General > Startup Disk, although I’m not sure why you would want to. If the Target really is near-dead, though, the only way you could engage this mode is to hold the T key during startup until the Thunderbolt symbol appears on its display.

The Target and Host must now be connected using a Thunderbolt 3 or 4 cable, although in Catalina and earlier a USB or USB-C cable could be used instead.

Shortly after they’re connected and ready, the Target’s internal Data volume should mount in the Host’s Finder. You should then be prompted for its FileVault password, and given access to it. As with Apple silicon Macs, you can also copy files from the Host to the Target. To disconnect the Host and Target, eject the Target’s volume from the Host, then press and hold the Power button on the Target to shut it down.

DFU mode

If you’re unable to put your ailing Mac into Recovery, or Fallback Recovery, it’s still possible that it has entered DFU mode, or could do so when started up to engage that mode. This is explored in more detail in this article, but sadly that doesn’t give you access to the contents of the Mac’s internal storage, except to wipe it and start from scratch.

Summary

• Required: a Thunderbolt 3 or 4 cable connecting the two Macs back-to-back.
• Apple silicon Mac: Recovery mode, Utilities menu, Share Disk.
• Intel T2 Mac: T key held during startup.
• Eject the Target’s disk on completion.
• Apple silicon Mac: disconnect button, then shut down.
• Intel T2 Mac: hold the Power button to shut down.