Which USB-C cable do you need to connect two computers?

Use a certified Thunderbolt 4 or USB4 40Gbps cable, 1 m or shorter, and check that both computers have Thunderbolt or USB4 ports. A 10 Gb/s USB-C data cable also links two computers at lower speed. The charging cable that came with a phone usually won’t link them at all.

USB-C cables all look alike, cost anything from a few dollars to over a hundred, and are often labelled inconsistently or not at all. With the wrong one, the computers either don’t connect or run at a fraction of the speed.

Why this is harder than it should be

Identical plugs. A charging cable and a 40 Gbps Thunderbolt cable look the same.
Confusing names. USB 3.2 Gen 2, USB4 20Gbps, Thunderbolt 3, 4 and 5 all describe USB-C cables with different abilities.
Missing labels. Many cables have no speed marking, and the ones in drawers rarely come with packaging.
Length matters. Longer passive cables drop to lower speeds. Longer 40 Gbps cables are active, with electronics inside, and cost more.
The ports matter as much as the cable. Both computers need Thunderbolt 3 or newer, or USB4. A plain USB-C port can’t link two computers, whatever the cable.
The cable only gives you a network. Plugging in doesn’t show the other computer’s files. You still set up file sharing on one computer and sign in from the other.

Which cables work

Cable	Speed	For two computers
Thunderbolt 5	80 Gb/s	Works. More than today’s computer-to-computer links use
Thunderbolt 4	40 Gb/s	Best choice for most people
USB4 40Gbps	40 Gb/s	Works
Thunderbolt 3	40 Gb/s, or 20 Gb/s on longer passive cables	Works
USB4 20Gbps	20 Gb/s	Works, at half the speed
USB 3 (10Gbps) data cable	10 Gb/s	Works between Thunderbolt ports, at about a quarter of the speed
USB 2.0 or charging cable	0.48 Gb/s or none	Won’t work

Speeds are the cable’s rating in each direction. Copies run slower: in our tests a 10 Gb/s link copied at about 8 Gb/s. See our test results.

Some computer pairs bring up only one 20 Gb/s lane, even on a 40 Gbps cable. In our tests a Linux laptop and a Mac did this, and the link carried 16.3–17.8 Gb/s. A better cable doesn’t change that.

How to tell them apart

Lightning bolt on the plug: Thunderbolt. A number beside it (3, 4 or 5) gives the version.
“40Gbps” or “20Gbps” on the plug or packaging: USB4 at that speed.
“10Gbps” or “SS10”: USB 3.
No marking, and it came with a phone or charger: assume USB 2.0.

What to buy

Buy a certified Thunderbolt 4 cable, as short as is practical, usually 1 m or less. It works with Thunderbolt 3, Thunderbolt 4 and USB4 computers. Then check both computers with how to tell if your laptop has Thunderbolt or USB4.

Check the cable made a link

Plug the cable into both computers, then look for the new network connection:

Mac: in System Settings, choose Network. Thunderbolt Bridge shows a green dot when the link is up.
Windows: in Settings, choose Network & internet > Advanced network settings. A new Ethernet adapter, such as Ethernet 2, appears under Network adapters.
Linux: in a terminal, run ip addr show thunderbolt0. If the device doesn’t exist, the link isn’t up.

If one computer starts charging the other but no connection appears, suspect the cable or one of the ports. Try a cable from the table above, or another port. For more checks, see two laptops connected with USB-C and nothing happens.

With the link up, you share a folder on the computer that has the files and connect to it from the other one. These are the steps with the sharing built into each system.

Share a folder

On a Mac: in System Settings, choose General > Sharing and turn on File Sharing. Click the info button next to it and add the folder. If a Windows PC will connect, click Options… and, under Windows File Sharing, select your account and enter its password.
On Windows: in Settings, choose Network & internet, then the cable’s Ethernet connection, and set Network profile type to Private network. Then, in Advanced sharing settings, turn on Network discovery and File and printer sharing. In File Explorer, right-click the folder, choose Properties, and on the Sharing tab click Share….
On Linux: install and set up Samba, with a Samba password for your user. The steps depend on your distribution.

Windows treats a new cable connection as a Public network, where discovery and file sharing stay off. If Windows offers to turn on network discovery for all public networks, set the cable to Private instead.

Find the address

With no router on the cable, each computer gives itself an address starting with 169.254. That’s normal. On the computer with the files:

Mac: in Network, choose Thunderbolt Bridge > Details… > TCP/IP.
Windows: open Terminal, run ipconfig, and find Autoconfiguration IPv4 Address under the cable’s Ethernet adapter.
Linux: run ip -4 addr show thunderbolt0. If there’s no inet line, open the wired connection’s settings and set IPv4 to Link-Local Only.

Connect and sign in

From a Mac: in Finder, choose Go > Connect to Server…, type smb:// and the address, such as smb://169.254.20.30, and sign in as a Registered User.
From Windows: in File Explorer’s address bar, type \\ and the address, such as \\169.254.20.30, then enter the user name and password in Enter network credentials.
From Linux: in Files, open Other Locations or Network, and type smb:// and the address in Connect to Server.

You sign in with an account on the computer that has the files. On a Windows PC with a Microsoft account, that’s the account’s email address and password, not the Windows Hello PIN.

The full walkthrough is in two laptops connected with USB-C and nothing happens.

What still slows a good cable down

Wi-Fi takes the copy. If both computers are on Wi-Fi and you connect by name, the name can lead to the Wi-Fi address, and the copy runs over the air. Connect by the 169.254 address.
The address changes. After unplugging or a restart, the self-assigned address can change, so a saved connection stops working.
It doesn’t reconnect. After sleep, a restart or unplugging, you connect and sign in again.
Small files are slow. File sharing handles each file with separate requests. In our tests, SMB took almost four minutes to copy 20,000 small files over a 10 Gb/s cable.
SMB signing. Windows 11 version 24H2 and later require SMB signing by default, which adds work to every request.

For the reasons behind these, see why file sharing over Thunderbolt runs below the cable’s speed.

Plug in the cable and skip the sharing setup

DirectConnect uses the same Thunderbolt or USB4 cable without file sharing. Install it on both computers and plug in, and the other computer’s files open in Finder, File Explorer or your Linux file manager like a USB drive.

Works with the cables above. A Thunderbolt or USB4 cable gives the most speed, and a USB-C data cable also works, at up to 10 Gb/s.
No sharing settings. You leave File Sharing, the Windows network profile and Samba alone. Your computer may ask for permission the first time DirectConnect runs.
No accounts or passwords. On each computer, you choose what it shares: Share drives, Share a folder or Receive only.
No addresses. The computers find each other over the cable, and the other computer appears by name. You don’t look up or type 169.254 addresses.
Reconnects by itself. Turn on Remember this computer, and the two computers connect the same way whenever you plug the cable back in.
Built for small files. In our tests, fast copy moved 2,000 small files between two Macs in 0.25–0.52 s.
Gets more from a faster cable. Fast copy sent a 1 GiB file between two Macs at 12.5–20.7 Gb/s on a 40 Gbps cable, and copied at about 8 Gb/s on a 10 Gb/s cable.

Try DirectConnect