How Universal Control works on macOS Monterey


The best moment of this year’s WWDC keynote was a simple demo of a macOS feature, Universal Control. The idea is simple enough: you can use the keyboard and trackpad on a Mac to directly control an iPad, and it even makes it easy to drag and drop content between those devices.

What made the demo so impressive is how easy and seamless it all seemed. In a classic Apple move, no installation was required at all. The segment happened so quickly that it even seemed (wrongly, it turns out) as if the Mac could physically locate the iPad in space so it knew where to place the mouse pointer.

After Zapruning the clip and asking Apple a few questions, I now have a better understanding of what’s going on here. It turns out that the whole system is actually simpler than it seems at first glance. It’s essentially a new way to use some of the technologies that Apple had already developed. That’s no knock on Universal Control – sometimes the best software features are the result of smart thinking rather than brute force technological improvements.

So this is what happens in that demo.

First, you need to get the iPad and Mac relatively close together. Universal Control builds on the same Continuity and Handoff features that have long been part of iOS and macOS. When the devices are close enough, their Bluetooth modules will let each other know. Of course, all devices here need to be on the same iCloud account for this to work.

Next, launch Universal Control by dragging your mouse pointer all the way to the left or right edge of your Mac’s screen and then slightly out there that edge. If you do, the Mac will assume you’re trying to drag the mouse to another device, in this case the iPad.

So there is no UWB location detection, just a good old assumption. One note is that if you have many compatible devices, Monterey assumes you’re dragging to the last iPad or Mac you interacted with.

At this point, a Wi-Fi Direct connection is established and the iPad shows a small bar on the side with a small bump. It’s kind of an indicator that the iPad knows you’re trying to drag a mouse into it. Keep dragging and polishing, the bump breaks loose in a circular mouse pointer. When the mouse is on the iPad screen, both the mouse and keyboard on your Mac control the iPad. Move it back to the Mac and you control the Mac.

But there’s a clever little allowance built into that odd bar. There’s a couple of arrows in it, hinting that you can slide that bump up or down before it breaks loose inside the iPad itself. That way, you’ll align the iPad’s screen with your Mac’s, so dragging the mouse between the screens doesn’t cause a weird jump.

You go through the same process to set up a second device with Universal Control – it’s up to three. If all these automatic settings sound like a hassle, you can just head into System Preferences and set a device as your favorite Universal Control buddy gadget.

However you set it up, you can drag and drop content between devices and it uses Wi-Fi Direct or USB to transfer the files. Of course, if you’re dragging files to the iPad, make sure you have an app open (like Files) that can accept it.

That’s pretty much the long and the short of it. There are still some details to work out, Apple says, and it’s not available in the initial developer preview. For example, if you place your dock on the left or right side of the screen, it’s unclear if this whole setup will work.

What fascinates me about this system – as I discuss in the video above – is that it’s only really possible because of a long line of software improvements built into the iPad over the years, including:

  1. Continuity, transfer and AirDrop. Universal Control isn’t technically AirDrop, but it’s the same basic idea. These are all the basic ways Apple devices communicate with each other directly rather than through the cloud.
  2. Multitasking. I’m not talking about split screen, but the drag-and-drop support that came with the improved window options on the iPad.
  3. Keyboard and mouse support. That’s an obvious requirement, but it wasn’t always clear that Apple would put mouse support in the iPad.
  4. sidecar. Sidecar is the tool that lets you use an iPad as a second Mac monitor. I don’t think Universal Control uses the same bits of software as Sidecar, but I do think there were probably lessons about latency that would be helpful here.

I suspected there would be a similar evolution story on the Mac side of this story. I thought all the iPad and iOS technologies that made their way to the Mac with the last few releases played a part. Catalyst apps became native iPad apps for M1 Macs. Control Center, Shortcuts, and Focus Mode are all iOS stuff that’s also on the Mac.

Nice idea, but wrong. Apple tells me that the basics on the Mac side are as simple as it looks, based on Continuity and Handoff.

I hope Universal Control works just as well in the real world as it does in this staged demo – and I know that’s not certain. But what I like about the feature is that it’s just a clever recombination of existing technologies that Apple had already built for other purposes.

Within the Apple ecosystem, you expect the trade you make for just using Apple devices to get synergistic integrations like this one. They are actually rarer than I thought in recent years. But as the Mac and iPad continue to share features with each other, I expect we’ll see more of it in the future.