Universal Control. Your Mac runs your iPad. Your Mac runs… your other Mac. It’s just… Total. Ecosystem. Escalation. And this is how it works…
Time was, if you slid your iPad up next to your Mac, and you wanted to control it, you had to reach over and do it directly… tap, type, swipe… Like an animal.
Now, with the upcoming macOS Monterey and iPadOS 15, you can just take it over with Universal Control.
Time was, if you slid your iPad up next to your Mac, and you wanted to control it, you had to reach over and do it directly… tap, type, swipe… Like an animal.
Now, with the upcoming macOS Monterey and iPadOS 15, you can just take it over with Universal Control. It’s a Continuity technology, like Handoff, Universal Clipboard, and Sidecar. And, it has the exact same requirements as Sidecar in terms of Bluetooth radios and Apple custom accelerator chips. But, basically, if you can use Sidecar, you can use Universal Control.
And then… let’s say you have your MacBook and you get a shiny new iPad, and log into it with your Apple ID. As soon as those two devices come into proximity, they’ll pair using Bluetooth Low Energy, or BTLE.
The pairing is done out-of-band, which means separate from any other communications, and end-to-end encrypted using Apple’s Push Notification Service protocol – APNs, which is the system responsible for all the internet-based notifications you get on all your devices.
So… just imagine your MacBook and iPad start sending these secret little iMessages between them to set things up for you.
Once the pairing happens, each device generates a symmetric key that’s encrypted using 256-bit AES, — Just… really strong encryption — and each stores it in its own Keychain, which is the system Apple uses to securely store credentials like passwords.
Those keys are then used to encrypt and authenticate the BT LE broadcasts between the devices.
Apple also measures time of flight, or how long the transmissions take between the devices, to make sure your iPad really is close to your Mac, in other words you have physical possession and oversight of both devices, but also to make sure some theoretical evil-doer isn’t sitting in the middle, trying to record the broadcast on one end and relay or replay it to another device on the other end.
Once the pairing is established and secured, your devices will then use Bluetooth LE to advertise their current activity, protected by 256-bit encryption, in Galois/Counter or GCM Mode, which helps balance security and performance.
And not just to sync data, like you’d see with Google Docs open on two computers at the same time. But activity and state.
It’s how you can start an email on your iPhone, tap the Continuity Email icon on your Mac, and not have to go look for the app or to a website and navigate to the file you want to open, and then scroll to where you left off, but just one tap or click and you’re e taken right to that email, right to the exact spot, ready and able to continue typing immediately.
Or how you can take a screenshot on your iPhone, hit copy, and instantly paste it into a doc on your Mac. Or some text. Or vice versa.
And it’s how you can drag the cursor on your Mac to the edge of the screen, keep on dragging, and have it pop up on your iPad.
And that’s it. You’re in Universal Control mode. That’s all. Zero setup.
Now, yes, you do have to start the drag on you Mac… which… is a drag. You can’t initiate Universal Control on the iPad, at least not yet.
But once you start the drag on your Mac, the way Apple figures out where your iPad is relative to your Mac is very… take a pencil into space.
I’m sure they prototyped all sorts of time-of-flight and acoustic pattern models to actually figure out where exactly in time and space each device is relative to the other, and I’m just as sure that eventually every device will have a U1 or similar chip in it, which will just know where every other things is… always.
But for now, Apple is just counting on us to know. That the direction we drag the cursor is the direction of the iPad.
And sure, that means we’ll see some prank videos and articles of people deliberately dragging the wrong way and saying ha ha, silly Apple, it’s all broken! And just, ok fellow kids.
When you drag your cursor to the edge of your Mac screen, and keep dragging, the continuity system detects that through everything I just described, and your iPad responds by bringing up a special… cursor membrane indicator on the side that’s close to your Mac.
And, yeah, if you just happen to be captain iPad or Ozimandias or something, and have multiple iPads setup on the same side of your Mac, it’ll just assume you want to use whichever of those iPads you last used. Whichever last registered activity on the Continuity system.
Apple then switches from Bluetooth LE to their own peer-to-peer don’t-call-it-Wi-Fi-direct ad hoc wireless connection, similar to how it handles AirDrop or Handoff or Sidecar. That connection is encrypted using TLS, which exchanges and verifies iCloud identity certificates, and, from then on, sends any large data payloads over Wi-Fi because so much faster. What I’m not sure about just yet is whether or not that connection persists, like an encrypted, encoded Sidecar stream, or is created opportunistically and temporarily only when large amounts of data are being transferred. So… TBD.
Either way, any way, tt that point, you can swipe straight through and just start controlling your iPad, or, you can use that initial cursor indicator — the Mac… or iPad icon on it — to adjust the level for the cursor, so if you iPad is slightly higher or lower than your Mac, you can set what you want to be considered level, so when you begin swiping back and forth, the cursor stays exactly where you expect it to.
Either way, from then on, your Mac mouse or trackpad can control your iPad as if it were the iPad’s mouse or trackpad. It doesn’t take over the display like AirPlay or Sidecar and make it another display for your Mac, it’s still your iPad in every way, you’re just controlling it with your Mac.
One trackpad and keyboard to rule them all.
Universal Control also acts a visual interface for Universal Clipboard, so instead of having to copy something on your iPad and paste it on your Mac, you can just drag it from your iPad and drop it right onto your Mac. And pretty much anything you can drag, you can drop.
You can also slide in another iPad on the other side if you want, or, say, another Mac, a fancy new M1 iMac, whatever. Then you can control everything with either one of the Macs trackpads, mouses, or keyboards. Even drag and drop across any and all desktops.
Now, if that’s not what you want. If you want to just take over the iPad screen, you have Sidecar for that. Works the same as always. You just click on the display preferences on the Mac, select your iPad as the Sidecar target, and then your iPad becomes a suped-up second display for your Mac. Send a second, virtual display to your iPad using an encrypted encoded stream. Using pretty much the same technology I just described, Bluetooth LE for initial handshake, and then point-to-point Wi-Fi for serious data transfer.
But now, also new with macOS Monterey, your Mac can become a second display for another Mac or even an iPad or iPhone… with AirPlay for Mac. It basically just turns your Mac display into an AirPlay target, like an Apple TV attached to a TV. That uses AES encryption for either a video stream or mirroring. As long as you’re on the same network, and you authenticate a verify the same as any other AirPlay connection, that tiny MacBook Air or enormous iMac or ProDisplay XDR screen becomes yours.
Now, it’s not a perfect replacement for the long lost, much-lamented Target Display Mode because AirPlay has some latency to preserve sync, but for a lot of applications, that really won’t matter. And until Apple gets its Target Display Mode act back together, which who knows how long that could be, does kinda make using an old or extra Mac display as a second display.
Which, hurray!
Now, there’s also AirPlay for Mac to talk about, but that’s a real tangent for this video, so I’ll save it for the Nebula cut, where I don’t have to worry about YouTube view durations or retention or views per viewer… or any of that stuff.
It’s where I post all my videos ad free, sponsor free, and many of them with extended, bonus content. Sometimes twice or three times as long, like event reactions, interviews, explainers, and more.