How to Use Target Disk Mode to Transfer Files Between Macs

When you purchase a new Mac, the first task is migrating all the data from your old machine. While Apple provides an excellent “Migration Assistant” tool that operates over Wi-Fi, transferring hundreds of gigabytes of photos, videos, and applications wirelessly can take an entire day. If the wireless connection drops, you risk data corruption and must start over.

For the fastest, most reliable data transfer possible, power users rely on a hardware-level feature unique to Apple computers: Target Disk Mode. This feature allows you to connect two Macs with a physical cable and forces the old Mac to behave exactly like an external hard drive.

What You Need Before Starting

To use Target Disk Mode, you need the correct physical cable to connect the two machines. You cannot use a standard USB-A charging cable.

• If both Macs have Thunderbolt 3 (USB-C) ports, you must use a high-speed Thunderbolt 3 or Thunderbolt 4 cable. Note: The white USB-C charging cable that comes in the MacBook box is designed for power, not data, and will result in agonizingly slow transfer speeds. Ensure the cable has the Thunderbolt logo (a small lightning bolt) on the connector.
• If you are connecting an older Mac with Thunderbolt 2 to a newer Mac with Thunderbolt 3, you will need a Thunderbolt 3 to Thunderbolt 2 adapter.

How to Boot into Target Disk Mode

You must prepare the “Source” Mac (the older machine containing the data you want to copy) before connecting it to the “Target” Mac.

1. Shut down the Source Mac completely (Apple menu > Shut Down).
2. Press the Power button to turn the Mac back on, and immediately press and hold the T key on the keyboard.
3. Keep holding the T key until you see a Thunderbolt or USB icon floating on a dark screen. This visual confirms the Mac has successfully entered Target Disk Mode and is waiting for a connection.

Note for Apple Silicon (M1/M2/M3) Macs: The process is slightly different. Shut down the Mac. Press and hold the Power button until you see “Loading startup options.” Click Options, click Continue, enter your administrator password, select Utilities from the top menu bar, and choose Share Disk.

Connecting the Two Computers

Now that the old Mac is ready, you can make the physical connection.

1. Ensure your new “Target” Mac is turned on and logged in normally.
2. Plug one end of your Thunderbolt cable into the Source Mac, and the other end into the Target Mac.
3. Wait a few seconds. The hard drive of the Source Mac will suddenly mount and appear on the Desktop (or in the Finder sidebar) of the Target Mac, just as if you had plugged in a USB flash drive.

Transferring the Data

Because the connection is happening at the hardware level over a Thunderbolt cable, the data transfer speeds are monumental. You can now use macOS Migration Assistant on the new Mac, and point it directly at the mounted hard drive of the old Mac.

Alternatively, you can manually open the drive in Finder and drag-and-drop specific folders (like your Documents or Pictures folders) straight to your new machine.

Safely Ejecting the Drive

Just like any external hard drive, you must safely eject the Source Mac before unplugging the cable to prevent data corruption.

1. On the new Target Mac, locate the mounted drive icon on the Desktop or in the Finder sidebar.
2. Right-click the icon and select Eject (or drag the icon to the Trash can in the dock).
3. Once the icon disappears from the screen, it is safe to unplug the physical cable.
4. Finally, hold down the Power button on the Source Mac for several seconds to force it to shut down and exit Target Disk Mode.