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How to transfer files between two computers with a USB-C cable

A USB-C cable can connect two computers only if both have Thunderbolt or USB4 ports. With those ports, the cable becomes a fast network link, and you share files over it with each computer’s built-in file sharing. Ordinary USB-C ports can’t talk to each other, which is why plugging two laptops together often does nothing at all.

Why this is harder than it should be

  • Plugging in does nothing. No drive appears and no message explains why. At most, one laptop starts charging the other. See why nothing happens.
  • The ports and cables look identical whether they can connect two computers or not.
  • The cable only creates a network connection. You still turn on file sharing, set up an account and password, change network settings on Windows, find an address and sign in.
  • Each operating system does it differently. The settings, the address format and the sign-in all change between Mac, Windows and Linux.
  • It doesn’t last. Unplug, sleep or restart, and the shared folder disconnects.
  • Folders of small files crawl over file sharing, even on a fast cable.

1. Check both computers’ ports

USB-C is the shape of the plug. What the port can do varies. You need Thunderbolt 3 or newer, or USB4, on both computers.

  • Look next to the port for a lightning bolt, or a “USB4”, “40Gbps” or “20Gbps” label.
  • On a Mac, open System Information and look under Thunderbolt/USB4. Most recent Macs have Thunderbolt ports, but some desktops have extra USB-C ports that don’t.
  • On a Windows PC or Linux laptop, search for the model number with “specifications” and look for Thunderbolt or USB4.

For more detail, see how to tell if your laptop has Thunderbolt or USB4.

2. Use a data cable

Use a Thunderbolt 3, 4 or 5 cable, or a USB4 cable. A 40 Gbps cable gives the most headroom. The cable that came with a phone is often a USB 2.0 charging cable and won’t work. A 10 Gb/s USB-C data cable also works, at about a quarter of the speed. See which USB-C cable you need.

Plug the cable into both computers. Each one adds a new network connection for the cable:

  • Mac: in System Settings, choose Network. Thunderbolt Bridge shows a yellow dot and Self-Assigned IP. That’s normal: there’s no router on the cable, so the Mac gives itself an address starting with 169.254.
  • Windows: in Settings, choose Network & internet > Advanced network settings. A new Ethernet connection, such as Ethernet 2, appears under Network adapters, usually described as USB4(TM) P2P Network Adapter.
  • Linux: a thunderbolt0 connection appears in Settings under Network. If it has no IPv4 address after a minute, open its settings and set IPv4 to Link-Local Only, because no DHCP server answers on the cable.

If no new connection appears, one of the ports or the cable doesn’t carry the link. Try another port before anything else.

4. Share a folder on the computer with the files

The other computer signs in with an account on this one, so you need its user name and password. A PIN or Touch ID doesn’t count.

On a Mac

  1. In System Settings, choose General > Sharing and turn on File Sharing.
  2. Click the info button next to File Sharing. Under Shared Folders, click + to add the folder, and set who can read or write it under Users.
  3. If a Windows PC will connect, click Options…, select your account under Windows File Sharing and type its password. Windows can’t sign in until you do.
  4. Find the address: in Network, choose Thunderbolt Bridge, click Details… and note the IP address under TCP/IP.

On a Windows PC

  1. In Settings, choose Network & internet, then the cable’s connection. Under Network profile type, select Private network. Windows puts the cable on a Public network, where sharing is blocked.
  2. In Advanced network settings > Advanced sharing settings, turn on Network discovery and File and printer sharing under Private networks.
  3. In File Explorer, right-click the folder, choose Properties, and on the Sharing tab click Share…. Add your account, set Read/Write if needed, and click Share.
  4. Find the address: run ipconfig in Terminal and note the Autoconfiguration IPv4 Address of the cable’s adapter. It starts with 169.254.

With a Microsoft account, the user name is its email address and the password is the account password, not the PIN. For the full Windows walkthrough, see connecting two Windows PCs with USB4.

On a Linux computer

Linux desktops don’t share folders with a Mac or Windows PC out of the box. You install and configure Samba, set a separate Samba password and open the firewall. It’s usually simpler to share from the Mac or PC and connect from Linux. The Mac and Linux guide covers both ways.

5. Connect from the other computer and sign in

Use the cable’s 169.254 address, not the computer’s name. A name can find the computer’s Wi-Fi address instead, and the copy then runs over Wi-Fi.

  • From a Mac: in Finder, choose Go > Connect to Server…, type smb:// and the address, for example smb://169.254.20.30, and click Connect. Choose Registered User, type the user name and password, then choose the shared folder.
  • From Windows: in File Explorer’s address bar, type \\ and the address, for example \\169.254.20.30, and press Enter. Type the user name and password in Enter network credentials.
  • From Linux: in Files, press Ctrl+L, type smb:// and the address, and press Enter. Choose Registered User and sign in.

The shared folder opens in your file manager. Drag files across.

After sleep, a restart or unplugging

The shared folder works only while the cable link is up. When either computer sleeps or you unplug the cable, the folder disconnects, and copies in progress stop with an error.

  • After sleep or replugging: wait for the cable connection to come back, then connect and sign in again.
  • After a restart: saved and mapped connections can fail, because the cable link comes up after you sign in. Open them again by hand.
  • If the address changed: self-assigned addresses can change after you unplug, so look it up again on the computer with the files.

See why a network share disconnects after sleep.

If copies are slow

  • The copy is on Wi-Fi. If you connected by name, reconnect by the cable’s address. On Windows, the Performance tab in Task Manager shows which connection carries the traffic. On a Mac, Activity Monitor’s Network tab shows the total but not the connection.
  • The folder has many small files. File sharing opens, writes and closes each file in turn. In our tests, a Mac took 114 seconds to copy 20,000 small files (331 MB) from a Samba share over a 10 Gb/s cable, and 238 seconds to copy them to it.
  • Every request is signed. Windows 11 version 24H2 requires SMB signing by default, which adds work to every request.
  • The link is uneven. In our tests on a 40 Gb/s USB4 link, a Mac sent a Windows PC 24.2 Gb/s, but the PC sent the Mac 12.0 Gb/s, before any file copying.

Large files fare better. A 40 Gb/s Thunderbolt link carries up to 40 Gb/s in each direction, and between two Macs we measured 37.7 Gb/s each way on the cable itself. Copies run slower, because the drives set a limit too. Our test results have the details.

Without Thunderbolt or USB4 ports

With a USB transfer cable

If the ports are plain USB-C, a USB transfer cable is the cable option. It has a small chip in the middle and comes with its own copy software. It’s slower than Thunderbolt, and the software decides which operating systems are supported, so check that before buying.

With an external drive

Copy the files to a drive, move the drive, then copy them off. It works between any two computers, but every file is copied twice and the drive needs enough free space. Format it as exFAT if it has to work on both Mac and Windows.