DirectConnect

Guides

Use a laptop as an external drive for another computer

A laptop can’t act as a USB drive for another computer on its own. Between two Macs, Share Disk or Target Disk Mode come closest, but the shared Mac can’t be used meanwhile. Between any other pair, the built-in route is network file sharing over a cable or Wi-Fi.

Why this is harder than it should be

  • Laptops are hosts, not drives. A computer’s USB ports are built to use drives, not to behave like one. Two computers plugged together both expect to be in charge, so nothing appears.
  • Target Disk Mode is gone on new Macs. Intel Macs could start up as an external disk. Macs with Apple silicon replaced it with Share Disk, which shares the disk as a network share instead.
  • The Mac methods take the Mac out of action. Both restart the Mac into a special mode, and it can’t be used until you restart it normally.
  • They only work between Macs. Windows and Linux have no equivalent, and a Windows PC can’t read a Mac’s disk without extra software.
  • File sharing is a setup job. Keeping the laptop usable means turning on sharing, choosing folders and accounts, setting the network profile and finding addresses.
  • Network shares don’t behave like a drive. They drop after sleep, ask you to sign in again, and slow down with folders of small files.

On a Mac with Apple silicon: Share Disk

Share Disk makes the whole disk of one Mac available to another Mac. Connect the two Macs with a Thunderbolt or USB4 cable first. On the Mac you want to share:

  1. Shut down the Mac.
  2. Press and hold the power button until Loading startup options appears.
  3. Click Options, then click Continue.
  4. If asked, select an administrator account, click Next and enter its password.
  5. In the menu bar, choose Utilities > Share Disk.
  6. Select the disk and click Start Sharing.

On the other Mac:

  1. In Finder, click Network in the sidebar.
  2. Double-click the shared Mac, then click Connect As.
  3. Select Guest and click Connect. The disk opens in Finder.

When you’re finished, eject the disk on the other Mac. On the shared Mac, click Stop Sharing, then restart it from the Apple menu. Share Disk uses network file sharing, so large folders of small files copy slowly.

On an Intel Mac: Target Disk Mode

An Intel Mac with Thunderbolt can start up as an external disk for another Mac:

  1. Connect the two Macs with a Thunderbolt cable.
  2. On the Mac you want to share, open System Settings, choose General > Startup Disk, and click Restart in Target Disk Mode. On an older macOS, hold T while the Mac starts up instead.
  3. If the disk uses FileVault, enter its password when the other Mac asks. The disk appears on the other Mac’s desktop and in Finder.

When you’re finished, eject the disk on the other Mac, then press the shared Mac’s power button to turn it off. The shared Mac shows only a Thunderbolt symbol until then, so you can’t use it.

Share the laptop’s files and keep using it

Network file sharing keeps the laptop running normally and works between Mac, Windows and Linux. Over a Thunderbolt or USB4 cable, both computers see a new network connection: Thunderbolt Bridge on a Mac and an extra Ethernet connection on Windows. Without those ports, use Wi-Fi or Ethernet.

Turn on sharing on the laptop

  • On a Mac: in System Settings, choose General > Sharing and turn on File Sharing. Click the info button next to it, add folders under Shared Folders, and note the smb:// address shown. For a Windows PC, click Options… and select your account under Windows File Sharing.
  • On Windows: in Settings > Network & internet > Ethernet, select the cable’s connection and choose Private network. Then in Advanced network settings > Advanced sharing settings, turn on Network discovery and File and printer sharing for private networks. Right-click a folder, choose Properties > Sharing > Share…, pick an account and click Share.
  • On Linux: sharing a folder with Mac or Windows needs Samba installed and a Samba user set up. GNOME’s own File Sharing setting only shares your Public folder.

Connect from the other computer

  • On a Mac: in Finder, choose Go > Connect to Server…, type smb:// and the laptop’s address, and click Connect.
  • On Windows: in the File Explorer address bar, type \\ and the laptop’s address, such as \\169.254.10.20, and press Enter.
  • On Linux: in Files, choose Other Locations (Network in newer versions), type the smb:// address in Connect to Server, and click Connect.

Sign in with an account and password on the laptop. For a Windows account linked to a Microsoft account, use the email address and account password, not the Windows Hello PIN.

Common problems over a cable

  • The laptop doesn’t show up. Windows treats a new cable connection as Public, which hides the PC. Set it to Private network on both PCs.
  • The address starts with 169.254. With no router on the cable, each computer picks its own address. On Windows, run ipconfig in Terminal to find it. On a Mac, look in Network > Thunderbolt Bridge > Details… > TCP/IP.
  • The copy runs over Wi-Fi. If both computers are also on Wi-Fi, connecting by name can reach the laptop’s Wi-Fi address. Connect with the cable’s address instead.
  • Copies are slower than the cable. Windows 11 version 24H2 and later require SMB signing by default, which adds work to every transfer. Folders of small files are slowest. In our tests, network file sharing took almost four minutes to copy 20,000 small files over a 10 Gb/s cable.

After sleep, a restart or unplugging

A share closes when either computer sleeps, restarts or loses the cable. Neither macOS nor Windows reopens it on its own, so you connect and sign in again. A cable’s 169.254 address can also change when you plug back in, which breaks a share saved by address. To make reconnecting quicker, see how to keep a shared folder connected.