DirectConnect

Guides

How to tell if your laptop has Thunderbolt or USB4

Look for a lightning bolt or a “USB4”, “40Gbps” or “20Gbps” label next to the port, then confirm it in your computer’s system information. Only Thunderbolt and USB4 ports can connect two computers directly, and both computers need one.

Why this is harder than it should be

  • Same shape, different abilities. USB-C describes the plug. Behind it can be USB 2.0, several speeds of USB 3, USB4 at 20 or 40 Gb/s, or Thunderbolt 3, 4 or 5.
  • Missing or tiny labels. Many laptops, including every MacBook, print nothing next to their ports. Others use small icons that are hard to read.
  • Vague spec sheets. Listings often say “USB-C” or “USB 3.2” without saying whether a port supports Thunderbolt or USB4.
  • Mixed ports on one computer. A laptop can have one Thunderbolt port and one plain USB-C port. Some desktops have extra USB-C ports on the front that are plain USB.
  • A port that charges and runs a display can still be the wrong kind. Power and video work on plain USB-C ports too, so they don’t prove anything.
  • Both computers have to qualify. One Thunderbolt laptop and one plain USB-C laptop can’t connect directly.
  • The right ports are only the start. The cable gives you a network link. Moving files over it still means setting up file sharing on one computer and signing in from the other.

What the port labels mean

  • Lightning bolt: Thunderbolt. A number beside it gives the version. Works for a computer-to-computer connection.
  • “USB4”, “40Gbps” or “20Gbps”: USB4. Works.
  • “SS”, “SS10” or “10Gbps”: USB 3. Doesn’t work for a direct connection.
  • A plain USB symbol or no label: check with the steps below.

On a Mac

  1. Choose the Apple menu, then About This Mac, then More Info…. System Settings opens at About.
  2. Scroll to the bottom and click System Report…. Or hold Option and choose System Information… from the Apple menu.
  3. In the sidebar, under Hardware, select Thunderbolt/USB4. Each port is listed as a bus with its speed, for example “Up to 40 Gb/s”.

Most Macs from the last several years have Thunderbolt or USB4 ports on the back or sides. Some desktop Macs also have front USB-C ports that are plain USB, so use the ports System Report lists.

On Windows

  1. Open Settings, then Bluetooth & devices, then USB. If USB4 Hubs and Devices appears, the PC has USB4.
  2. If it doesn’t, right-click the Start button and choose Device Manager.
  3. Expand Universal Serial Bus controllers and System devices. Look for a USB4 host router or a Thunderbolt controller.
  4. If neither appears, search for the model number with “specifications” and look for Thunderbolt or USB4.

Many PCs with Thunderbolt 3 or 4 also come with the Thunderbolt Control Center app. If it’s installed, the PC has Thunderbolt.

On Linux

In a terminal, run:

ls /sys/bus/thunderbolt/devices

If it lists a domain0 entry, the computer has a Thunderbolt or USB4 controller. If the folder is missing or empty, it doesn’t, or the firmware has it turned off. On most desktop distributions, boltctl list shows connected Thunderbolt devices. Both commands only read.

Then check the cable

A Thunderbolt or USB4 cable rated 40 Gb/s gives the most headroom. Phone and charger cables are usually USB 2.0 and won’t carry the connection. See which USB-C cable you need.

Test it with the cable

Plugging the two computers together confirms both ports at once. If both qualify, each one gets a new network connection:

  • Mac: in System Settings, under Network, Thunderbolt Bridge shows a self-assigned address starting with 169.254.
  • Windows: in Settings, under Network & internet, a new Ethernet connection appears.
  • Linux: ip addr lists a thunderbolt0 interface.

If nothing appears on either computer, try another Thunderbolt or USB4 cable before ruling the ports out.

What setting up the built-in sharing takes

With the right ports and cable, you share files over the link the same way as on a home network. On the computer with the files, and then on the other computer:

StepMacWindowsLinux
Turn on sharingSystem Settings > General > Sharing > File SharingFolder Properties > Sharing > Share, plus Network discovery and File and printer sharingInstall Samba and add a share
Allow the connectionNothing extraSet the new Ethernet connection to PrivateOpen the firewall for Samba if your distribution runs one
Choose who signs inA user account on this MacA Windows account; with a Microsoft account, its email and password, not the PINA Samba user, set with smbpasswd
Find the addressNetwork > Thunderbolt Bridge > Details > TCP/IPipconfig, IPv4 address of the new adapterip addr show thunderbolt0
Connect from the other computerFinder > Go > Connect to Server, smb://addressFile Explorer address bar, \\addressFiles location bar (Ctrl+L), smb://address

Then sign in with the account from the third row and open the shared folder. These problems come up often:

  • Public network: Windows sets the new cable connection to Public, which hides the PC and blocks sharing until you change it to Private.
  • Self-assigned addresses: the cable link uses 169.254 addresses with no router behind them. They can change after you unplug, so a saved connection stops working.
  • Wi-Fi takes the copy: connecting by the other computer’s name can find its Wi-Fi address, so the copy runs over Wi-Fi instead of the cable. Connect by the 169.254 address.
  • SMB signing: recent versions of Windows 11 require SMB signing by default, which adds work to every request.
  • Small files: file sharing handles each file with separate requests. In our tests it took almost four minutes to copy 20,000 small files over a 10 Gb/s link.
  • Reconnecting: after sleep, a restart or unplugging, you connect and sign in again.

Step-by-step instructions for each pair are in how to transfer files between two computers with USB-C.