Use Your iPad As A Secondary Display In MacOS Catalina

One of the neater features you’ll find in macOS Catalina — one that definitely got my attention, at least — is Apple’s new “Sidecar” mode. Like a tiny seat attached to a larger motorcycle, Sidecar allows you to link your iPad to your Mac and use it as a secondary display. If you have an Apple Pencil, you can even interact with objects on the screen.

Since the feature is being tested as part of macOS Catalina, its exact nature might change once the final version of the OS ships out (this fall). Even now, Apple hasn’t listed which combination of devices support Sidecar, but here’s what people have pieced together as possibilities:

• Late 2015 27” iMac or newer

• 2017 iMac Pro

• Mid 2016 MacBook Pro or newer

• Late 2018 Mac mini or newer

• Late 2018 MacBook Air or newer

• Early 2016 MacBook or newer

• 2019 Mac Pro

As for iPads, any device that runs iPadOS should also be able to work with Sidecar, which means any iPad Pro, the fifth- and sixth-generation iPad, the iPad Mini (fifth-generation) and iPad Mini 4, and the iPad Air (third-generation) and iPad Air 2.

If your Mac isn’t on that list

You probably won’t be able to run Sidecar once the final version of macOS Catalina ships if your Mac is too old. Right now, you can get away with using a little loophole to try the feature out. Pull up Terminal in macOS Catalina and enter the following:

defaults write com.apple.sidecar.display AllowAllDevices -bool true; defaults write com.apple.sidecar.display hasShownPref -bool true; open /System/Library/PreferencePanes/Sidecar.prefPane

Once you hit Enter, your System Preferences should appear and the new “Sidecar” option should be visible. You might not like the quality of the Sidecar treatment, but you’ll at least be able to see what it looks like (conceptually). As one Redditor writes:

“I managed to make Sidecar work with my Mid 2014 MacBook Pro work and iPad Pro. It’s great in terms of minimal lag, but the image quality is bad. I guess the limitation is about hardware HEVC encoding which requires Intel Core 6th gen processor.”

Getting started with Sidecar

To get started with Sidecar, pull up System Preferences and look for the Sidecar option. Open it up, and you’ll see a pretty screen with a few basic options. You can connect to your device wired or wirelessly—your choice.

In this case, I’ve already selected my iPad from the drop-down menu that would otherwise appear under the giant image of an iPad. And in doing so, it automatically transforms my iPad’s display into an extended version of my desktop:

The upper-left icon on the left should, in theory, hide and show your toolbar. (I never got it to do anything.) The icon below it hides and shows your Dock—pulling it from your Mac to display it on your iPad, and vice versa.

The other icons should be fairly self-explanatory. Take special notice of the virtual Touch Bar at the bottom of your iPad’s display, though. Even if your Mac doesn’t have a Touch Bar, one will appear here for you to play with. Perhaps this will encourage you to upgrade or, conversely, remind you that Touch Bars are a little silly.

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Don’t use your fingers

As mentioned, you’ll need an Apple Pencil to interact with your display, and I don’t believe its pressure sensitivity applies in this mode (at least, it didn’t when I was testing it out with Affinity Photo). The taps you make are like left-clicks on your mouse; there’s no way to right-click or pull up a context menu, which can makes things feel a bit precarious if you’re trying to resize a window and close it accidentally.

You can, however, draw directly on your iPad in an app like Affinity Photo or Adobe Photoshop. While it’s not as elegant as simply completing your entire drawing on your iPad and sending it over to your Mac for additional editing, it’s at least a great way to do some quick touch-ups.

Switching apps between devices

I haven’t found a way to move your active windows between your two desktops using a keyboard command, but clicking and dragging the window is the easy option. You can also click on Window and then select “Move to…” to send an app between your Mac and your iPad (and back again).

Apple’s initial documentation for macOS Catalina lists a handful of apps that are compatible with Sidecar:

Don’t be fooled. Plenty of other apps can work on your secondary display, even if you might have to use them in a window instead of full-screen mode. That’s not so true for gaming, however. I got basic Steam games to work—the Jackbox Party Pack, for example—but more complicated titles wouldn’t load on my Mac at all. I didn’t have an issue playing games I downloaded from the App Store on either my Mac or my connected iPad, but I only really tested one title: Flappy Golf 2. I’ll be curious to see if any heavier hitters work well with Sidecar. I suspect they will not, given how much of your system is tied up with the dual-display setup.

Mixing Mac and iPadOS apps

One of the most interesting applications of Sidecar is that you can use it to interact with both Mac and iPadOS apps on the same screen. Since Sidecar is technically an app, itself, you can pin other apps on top of it (to the left or right of your iPad’s display) via Slide Over. You can’t Split View both Sidecar and another app, unfortunately, but you can at least manage the size of any open windows on your Mac so they aren’t hidden beneath the iPadOS app you’re sliding over.

Mirroring or extending your display

I also like how easy it is to extend or mirror your desktop display on your iPad, an option found in the traditional display icon in your toolbar. Note that switching to mirror mode will (temporarily) mess with your Mac’s resolution, but then you’ll be able to control a single screen with either your Mac or iPad—useful if you don’t want to deal with swapping apps back and forth all the time.

Sidecar is speedy

One of the best parts of Sidecar is how seamless the entire interaction can be. While this is undoubtedly affected by your wifi connection and/or the distance between your two devices (if you’re going wireless, like I did), I was impressed at how quickly you’re able to jump into Sidecar mode and the responsiveness of the Apple Pencil when you’re interacting with your iPad. Even though it has its quirks, Sidecar mode feels great to use.