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By Dan Moren

Speedy transfers with IP over Thunderbolt

Having multiple Macs sometimes feels like juggling. For the most part, I manage to maintain access to the files and data I want on both my MacBook Air and iMac using a combination of Dropbox, iCloud Drive, and cloud-based services. But in cases where I need to move very large files—say, for example, podcasts I’m editing in GarageBand—very quickly, I turn to a more manual approach involving *gasp* cables!

Right now Thunderbolt remains the fastest port on both my 2011-era iMac and my MacBook Air from 2014—even if it can’t reach its full speed of 10Gbps (or 20Gbps in the case of Thunderbolt 2), it can still transfer a multi-gigabyte file from one machine to the other in a matter of seconds. But using it to transfer files does take a few steps.

While you could use Thunderbolt Target Disk Mode, which essentially lets you boot one of your Macs as an external drive, I generally don’t feel like shutting down my computer just to transfer a file. Fortunately, there’s another option: Thunderbolt can converse via the same Internet Protocol (IP) used by Ethernet. It just takes a little quick configuration.

Fire up the Network pane of System Preferences. If there’s not already a Thunderbolt option in the list on the left-hand side, click on the Plus (+) button at the bottom, choose Thunderbolt Bridge from the Interface dropdown in the pane, and click Create. If necessary, repeat those same steps on the other Mac you’re using. Once those steps are done, you should never need to do them again.

To actually transfer a file, connect your two Macs via a Thunderbolt cable. After a moment you should see an IP address appear in the Thunderbolt section of the Network pane. (Make sure you leave “Using DHCP” selected.) It should be in the range, which signifies that it’s an IP address the computer has assigned to itself, rather than one assigned by your router.

Now for the slightly tricky part. In order to ensure that I connect over Thunderbolt, rather than my Mac’s default network interface of Wi-Fi, I manually note the Thunderbolt IP address of the Mac I want to connect to. On the other Mac I go to the Finder and choose Go > Connect to Server, then type afp:// (the x’s of course being replaced by that IP address you noticed earlier).1

When that connection goes through, a Finder window showing the computer you’re connecting to will open up as normal, but you should reap the benefits of the super-speedy connection. When you’re done copying your files, eject the volume as normal, unplug the cables, and you’re done.

Transferring files over Thunderbolt might seem like an extra hassle rather than just sending them over a wired or wireless Ethernet connection, and depending on your situation, that may indeed be the case. But next time you have to dash out of the house and realize you’ve forgotten to copy over your gigantic presentation or that season of TV shows you want to watch on the plane, you may be glad the option’s there.

  1. You can in theory circumvent some of this by making Thunderbolt the top priority interface by clicking the gear icon at the bottom of the list, choosing Set Service Order and dragging Thunderbolt to the top; then you can connect via your Mac’s Bonjour name. But in my experience it takes a little bit of time for Bonjour to recognize and switch to the Thunderbolt IP. Using the manual IP is more cumbersome, but faster.  ↩

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[Dan Moren is a tech writer, novelist, podcaster, and the Official Dan of Six Colors. You can email him at or find him on Twitter at @dmoren.]