Luna Display is a hardware solution that turns any iPad into a true, wireless second display for your Mac. Luna was designed and developed ex-Apple engineers and the makers of Astropad, award-winning drawing software that turns the iPad into a professional graphics tablet for Mac. Luna Display Introduces Mac-to-Mac Mode Luna Display: We're always looking for ways to give our users the freedom and flexibility that their workflow deserves. Luna Display's launch in the fall of 2018 blasted us off into an arena that no company had successfully played in before - we'd created a device that could turn your iPad into a second display for Mac.
Apple recently “Sherlocked” a company called AstroHQ, by that firm’s own acknowledgment, with a macOS 10.15 Catalina feature called Sidecar for converting an iPad into a secondary Mac monitor.
Sidecar essentially replicates the functionality of a physical Luna Display dongle that AstroHQ sells for $79.99—a seemingly steep price considering that Sidecar is free (see “Catalina’s Sidecar Turns an iPad into a Second Mac Monitor,” 21 October 2019, and “Luna Display Turns an iPad into a Responsive Mac Screen,” 7 December 2018).
So, what was AstroHQ to do? Company co-founder Matt Ronge took to Twitter earlier this month to announce Mac-to-Mac Mode for Luna Display.
If such a Mac-as-secondary-display set-up sounds vaguely familiar, you might be thinking of Apple’s own Target Display Mode, which does pretty much the same thing, but only under limited circumstances. You can use it to turn certain older iMacs into second displays for other Macs. But these setups tend to be temperamental.
TidBITS publisher Adam Engst used an older 21.5-inch iMac as a secondary display with his MacBook Air for a while, but the experience wasn’t entirely satisfying. He found that he often had to reinvoke Target Display Mode after the MacBook Air woke up, and he sometimes had to restart either the MacBook Air or the iMac to get it to work. Plus, it required keeping a keyboard attached to the iMac—purely to press Command-F2 to enable Target Display Mode—and while the iMac was hooked up, it somehow prevented audio from playing on the MacBook Air.
AstroHQ thinks the limited hardware requirements of Target Display Mode and its general flakiness give the Luna alternative an opening (shall we call it “Watsoning”?). For one thing, AstroHQ’s solution supports a wider range of dual-Mac scenarios—side-by-side MacBooks, for instance, or even a Mac mini with a MacBook functioning as its sole display.
But Mac-to-Mac Mode isn’t without its own issues. Most notably, although Mac-to-Mac Mode works with side-by-side iMacs, it doesn’t support either 21.5-inch or 27-inch iMacs with Retina displays—either 4K or 5K. That’s a shame, since it means you can’t use an older 27-inch iMac with Retina display as a 5K external monitor.
That said, Mac-to-Mac Mode does support standard 4K displays.
Getting Started with Mac-to-Mac Mode
AstroHQ sells two versions of its Luna dongle—a USB-C model for use with newer Macs, and a Mini DisplayPort version for use with older machines.
In addition to one of the dongles, Mac-to-Mac Mode set-ups require the following:
- A “primary” or host Mac, from which screen content will be projected to a secondary Mac. You plug the Luna dongle into this Mac, which must be running OS X 10.11 El Capitan or later.
- The secondary Mac, which must be running 10.8 Mountain Lion or later.
- Two Luna apps. You run the Luna Display app on the primary Mac and the Luna Secondary app on the secondary Mac. Both apps are free when you buy the Luna Display dongle.
- A reliable network connection. Most people will typically use Mac-to-Mac Mode over Wi-Fi with both Macs on the same wireless network. It also works over Ethernet, if both Macs are connected to the same Ethernet network.
Enabling a Mac-to-Mac connection is straightforward, as it tends to be with a Luna-initiated Mac-to-iPad connection.
First, launch the Luna Display app on your primary Mac. If you’re running 10.14 Mojave or later, you might be asked to modify Accessibility settings in System Preferences, but you should need to do this only once.
Second, open the Luna Secondary app on your secondary Mac. At this point, the two Macs should be able to link up automatically. After a bit of display flashing, your Desktop should expand from the primary Mac to the secondary Mac.
Automatic connections worked fine for me on some attempts, but not others for reasons I couldn’t discern.
If an automatic connection does not work, you can employ a workaround called Wi-Fi Manual Connect. Click this button in the apps on both Macs. You should then see a code appear in the app on the primary Mac. The same code also will show up in the app on the secondary Mac, but with a few digits omitted—fill those in, and you should be good to go.
Wi-Fi Manual Connect worked well for me when automatic connections failed. Adobe pdf printer mac download.
Once connected, you can use the Luna Display app on the primary Mac to tweak how the two Macs function in relation to each other, with the secondary Mac on the left or right. Clicking Custom dumps you into the standard Display settings for additional adjustments.
Using the Mac-to-Mac Mode
To test Mac-to-Mac Mode, I persuaded my wife to part temporarily with her trusty 2015 MacBook Air, which I paired with my 2018 Mac mini (see “It Lives! Apple Announces Pro-Focused Mac mini,” 30 October 2018) and its LG UltraFine external display (see “Apple Debuts LG’s All-New 23.7-inch UltraFine Display,” 20 May 2019).
With the MacBook Air in hand, I tested Mac-to-Mac Mode in three scenarios. Two of these involved the USB-C Luna Display dongle, and the third tapped the Mini DisplayPort version.
1: MacBook Air As Secondary Display
My goal here was to use my LG UltraFine display as the main screen for my Mac mini, with the MacBook Air off to one side as a secondary monitor, much as I would when using an iPad with the Luna Display.
This dual-screen setup worked well, with my Mac mini’s extended Desktop displaying on the MacBook Air with its full 1400-by-900-pixel resolution, and with good responsiveness.
The Mac-to-Mac Mode connection was impressively hard to break. I repeatedly closed and reopened the MacBook Air’s lid, with the Luna Display hookup continuing as if nothing had occurred. Putting the Mac mini to sleep did break the Mac-to-Mac Mode link, as you’d expect, but the Luna apps were waiting upon reawakening and automatically reinitiated the connection.
I did notice one bizarre anomaly. While both the MacBook Air’s built-in keyboard and the Mac mini’s external keyboard behaved as expected for text input, only the Mac mini’s mouse and trackpad acted normally. When using the MacBook Air’s trackpad, I couldn’t move the cursor onto the Mac mini’s display—It was notebook-only, for some reason.
2: MacBook Air As Primary Display
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What if you have a Mac mini as a “headless” Mac—tucked away in a closet, perhaps? Luna Display’s Mac-to-Mac Mode lets you use a Mac laptop as a wirelessly connected monitor whenever you need it. AstroHQ has already proposed using an iPad with a Mac mini in this way.
In my case, Mac-to-Mac Mode on my wife’s MacBook Air enabled me to use my Mac mini while on the comfy sofa far from my office.
Kaspersky antivirus free download. To test this single-display solution, I had to physically disconnect my LG screen from the Mac mini so that the MacBook Air would become the Mac mini’s sole display.
But first, a few macOS tweaks were required for this to function properly:
- Automatic login must be turned on via System Preferences > Users and Groups > Login Options. A pull-down menu at the top lets you designate a Mac account for automatic login. If the pulldown menu is grayed out, check if FileVault is turned on (it must be off) or if an iCloud password is used for authentication (which also disables automatic login).
- In that same Mac account, the Luna Display app must be set up to launch automatically on login (in System Preferences > Users and Groups > Login Items).
Once I had twiddled those settings, I rebooted my Mac mini while launching the Luna Secondary app on the MacBook Air. A few seconds later, the Luna apps on the Macs found each other, and—presto!—I was looking at the Mac mini desktop on the MacBook Air’s screen.
Everything worked reasonably well. Responsiveness was a bit slow but not bad. All input devices—the Mac mini’s Magic Mouse, Magic Trackpad, and Magic Keyboard, along with the MacBook Air’s built-in laptop keyboard and trackpad—behaved as expected. Dependability was decent; closing and reopening the MacBook Air’s lid had no effect on the Mac-to-Mac Mode link.
Because the MacBook Air and Mac mini connected over Wi-Fi, I was able to work anywhere within the range of my Wi-Fi network. In fact, I wrote much of this article on the MacBook Air in my first-floor living room, wrapped in a warm blanket on the sofa (because winter is nigh here in Minnesota), with the Mac mini running on the second floor in my home office. Sweet.
3: MacBook Air As Primary Computer
Until now, my Mac mini has served as the primary computer in my Mac-to-Mac Mode experiments, with my wife’s MacBook Air as a secondary display. But what if I flipped things around and made the MacBook Air my primary computer, with my Mac mini’s LG monitor serving as a secondary display for the MacBook Air?
That’s where the Mini DisplayPort version of the Luna Display dongle comes in. I plugged it into the MacBook Air for use with the primary Luna Display app, and then I ran the Luna Secondary app on the Mac mini. The goal was to extend the MacBook Air’s Desktop onto the LG display, via the Mac mini. At least, that was the idea.
Unfortunately, I could not get this setup to work reliably. The Mac-to-Mac Mode connection crashed repeatedly. At times I could move the cursor between displays, but at other times, it refused to move.
It was a mess, as AstroHQ’s Matt Ronge acknowledged when I got in touch. He said his team was scrambling to fix bugs that interfered with the use of the Mini DisplayPort model of the Luna for Mac-to-Mac Mode connections. I plan to check back on this and leave any updates in a comment below.
For now, though, although I can recommend the USB-C version of the Luna Display dongle with Mac-to-Mac Mode, if your main Mac only has a Mini DisplayPort or Thunderbolt 2 port, hold off for a bit.
Revisiting Luna Mac-to-iPad Mode
Dusting off my Luna dongles, months after writing about how they enable iPads as secondary Mac monitors, allowed me to revisit that scenario — and compare it to Apple’s equivalent, the Catalina Sidecar feature I reviewed just last month.
Because of Sidecar’s oddities, the Luna approach came as a relief in some ways. Of particular note: Using macOS with touch on an iPad screen is better with AstroHQ’s implementation. You can reach out and do just about anything with a fingertip — which seems sort of obvious, right? Ah, but as I detailed in my Sidecar review, fingertip interaction will work for some things on the iPad screen, and not others. In many cases, an Apple Pencil is required. Ugh.
So, for those who can afford the purchase of the Luna hardware, this is the best way to turn an iPad into a Mac display. Because Sidecar is free, though, most people will end up using that — which is fine since it works reasonably well, the touch issues aside, and should get better over time.
Mac-to-Mac Mode: Bottom Line
Using one Mac as a secondary display for another Mac will not have occurred to most users because, until now, this has been possible only under narrow circumstances involving specific iMac models. And, as Adam Engst notes, Apple’s Target Display Mode doesn’t work very well.
AstroHQ, scrambling to remain relevant after being Sherlocked, has therefore done the Mac world a huge favor with its Mac-to-Mac Mode. Though not yet fully baked, especially on the DisplayPort end, Luna hardware and its related software are a godsend for those with extra Macs ready to be repurposed as second displays.
This, of course, comes at a cost—the Luna dongles don’t come cheap, so every prospective user will have to weigh whether this is money well spent.
Extend or mirror your Mac desktop with Sidecar
- Make sure that your Mac and iPad meet the Sidecar system requirements.
- You can use Sidecar wirelessly, but to keep your iPad charged during use, connect it directly to your Mac with the USB charge cable that came with your iPad.
- Click the AirPlay icon in the menu bar on your Mac, then choose the option to connect to your iPad. Or use Sidecar preferences to connect.
If you don't see the AirPlay icon, choose Apple menu > System Preferences, click Displays, then make sure that ”Show mirroring options in the menu bar when available” is selected. - Your iPad should now show an extension of your Mac desktop. You can move windows to it and use it like any other display.
- To mirror your Mac display so that both screens show the same content, return to the AirPlay menu, which is a blue rectangle while using Sidecar. Choose the option to mirror your display. This is a great way to share your Mac screen with others.
- To end your Sidecar session, return to the AirPlay menu and choose the option to disconnect. Or click the Disconnect button in the sidebar on your iPad.
Learn more about using external displays. For example, you can use Displays preferences to arrange displays so that your iPad extends the left, right, top, or bottom of your desktop.
Move a window to your iPad display
If you hover your pointer over the full-screen button of a window, you can choose to move that window to or from your iPad display. It's faster than dragging the window, and the window is perfectly resized for your display.
The sidebar puts commonly used controls on the side of your iPad screen. It includes Command, Shift, and other modifier keys, so you can choose essential commands with your finger or Apple Pencil instead of a keyboard.
Use Sidecar preferences to turn off the sidebar or change its position.
Tap to show or hide the menu bar when viewing a window in full screen on iPad.
Command. Touch and hold to set the Command key. Double-tap to lock the key.
Option. Touch and hold to set the Option key. Double-tap to lock the key.
Control. Touch and hold to set the Control key. Double-tap to lock the key.
Shift. Touch and hold to set the Shift key. Double-tap to lock the key.
Undo the last action. Some apps support multiple undos.
Use the Touch Bar
Many apps on Mac have Touch Bar controls that make common actions even easier. With Sidecar, you get a Touch Bar on your iPad screen even if your Mac doesn’t have a Touch Bar. It works just like the Touch Bar on Mac, and you can tap its controls with either your finger or Apple Pencil.
Use Sidecar preferences to turn off the Touch Bar or change its position.
If the Touch Bar doesn't appear when using an app that offers Touch Bar controls, choose Apple menu > System Preferences, click Mission Control, then make sure that “Displays have separate Spaces” is selected.
Use gestures for scrolling and other actions
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Multi-Touch gestures on iPad remain available when using Sidecar. These gestures are particularly useful with Sidecar:
- Scroll: Swipe with two fingers.
- Copy: Pinch in with three fingers.
- Cut: Pinch in with three fingers twice.
- Paste: Pinch out with three fingers.
- Undo: Swipe left with three fingers, or double-tap with three fingers.
- Redo: Swipe right with three fingers.
Use Apple Pencil
To point, click, select, and perform tasks such as drawing, editing photos, and manipulating objects on your iPad while it's extending or mirroring your Mac display, you can use your Apple Pencil instead of the mouse or trackpad connected to your Mac. You can also use it to write, sketch, and mark up documents while seeing the updates live on your Mac.
Sidecar also supports double-tap, which you can turn on in Sidecar preferences. Double-tap enables apps that support this feature to perform custom actions when you double-tap on the side of your Apple Pencil (2nd generation).
Use a keyboard, mouse, or trackpad
During your Sidecar session, you can type using a keyboard connected to either your Mac or iPad, including the Smart Keyboard or Magic Keyboard for iPad.
To point, click, or select with a mouse or trackpad, use the mouse or trackpad connected to your Mac, or use an Apple Pencil on your iPad.
Use iPad apps
While using Sidecar, you can switch to an iPad app, then interact with that app on your iPad as you normally would. This suspends your Sidecar session until you switch back to the Sidecar app or disconnect Sidecar. The Sidecar app appears on your home screen only while using Sidecar.
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Use Sidecar preferences
Choose Apple menu > System Preferences, then click Sidecar. These preferences are available only on computers that support Sidecar.
- Show Sidebar: Show the sidebar on the left or right side of your iPad screen, or turn it off.
- Show Touch Bar: Show the Touch Bar on the bottom or top of your iPad screen, or turn it off.
- Enable double tap on Apple Pencil: Allow apps that support this feature to perform custom actions when you double-tap on the side of your Apple Pencil (2nd generation).
- Connect to: Choose an iPad to connect to, or click Disconnect to stop using Sidecar.
Sidecar system requirements
Sidecar requires a compatible Mac using macOS Catalina and a compatible iPad using iPadOS 13:
Mac using macOS Catalina
- MacBook Pro introduced in 2016 or later
- MacBook introduced in 2016 or later
- MacBook Air introduced in 2018 or later
- iMac introduced in 2017 or later, plus iMac (Retina 5K, 27-inch, Late 2015)
- iMac Pro
- Mac mini introduced in 2018 or later
- Mac Pro introduced in 2019
iPad using iPadOS 13
- iPad Pro: all models
- iPad (6th generation) or later
- iPad mini (5th generation)
- iPad Air (3rd generation)
Additional requirements
- Both devices must be signed in to iCloud with the same Apple ID using two-factor authentication.
- To use Sidecar wirelessly, both devices must be within 10 meters (30 feet) of each other and have Bluetooth, Wi-Fi, and Handoff turned on. Also make sure that the iPad is not sharing its cellular connection and the Mac is not sharing its Internet connection.
- To use Sidecar over USB, make sure that your iPad is set to trust your Mac.
Learn more
- Resolve Wi-Fi and Bluetooth issues caused by wireless interference, which can affect Sidecar performance when using Sidecar wirelessly.