The new sidecar function in macOS Catalina extends the display of your Mac to your iPad. It lets you use your iPad as a secondary monitor or as a mirrored display that works with Apple Pencil and accessories such as a mouse and keyboard.
How Sidecar Works
Once you have macOS Catalina installed on your Mac, you can connect your iPad to your computer and use it as an external display. It works in both wired and wireless modes.
Connecting your iPad with a USB-C or Lightning cable makes the connection faster and more stable. For most users, however, the wireless connection works just as well. There are no major delays since Apple uses its own Wi-Fi-based AirDrop-like peer-to-peer connection.
Sidecar only has a range of 10 feet. If you move to another room, you will notice a delay and a warning on the screen asking you to get closer to the Mac.
If you want to use the iPad as a portable display for a Mac in your home, do so. Take a look at Luna Display, which works on a Wi-Fi network and has a longer range.
Once Sidecar is activated, the iPad no longer works just as a monitor. You'll see a sidebar with controls and shortcuts and a virtual touch bar at the bottom of the screen. You can control the Mac display on your iPad with Touch, Apple Pencil and a mouse.
The touch interface works, but is not intuitive. If you were hoping that Sidecar turned your Mac into an iPad that you can use to tap and move your fingers on the screen, this is not the case. The UI elements in Mac were quite small for this to work reliably.
So, if you tap the screen with one finger or try to scroll with one finger, nothing happens. You have to use two fingers to scroll. The only way to click or tap items is to use the Apple stylus or a mouse connected to the iPad (which displays a cursor on the screen). Of course, the Mac's keyboard and trackpad work reliably.
Apple Pencil can not be used to navigate the interface. It can only be used to click and select on the Mac. Apple Pencil lights when drawing in supported apps on the screen. This works natively for the markup feature in preview with third-party applications like Affinity Photo, Adobe Illustrator and more on a new interaction model. Swipe with two fingers to navigate, click and choose with Apple Pencil or a mouse. The new text selection and editing gestures of iOS 13 and iPadOS 13 also work here.
RELATED: New features in macOS 10.15 Catalina, now available
Sidecar feature is supported on following Macs with macOS Catalina:
- MacBook Pro from 2016  MacBook Air from 2018
- iMac from 2016 plus iMac (Retina 5K, 27 inches, late 2015)
- iMac Pro
- Mac mini from 2018
- Mac Pro from 2019
and on the following iPads with Apple Pencil support on iPadOS 13:  iPad Pro: All Models
How to set up Sidecar
The Sidecar connection procedure is the same for wired and wireless connections. If you want to use the cable connection, first connect the Mac to your iPad using a compatible cable.
You can start the sidecar connection in several ways. It's best to use the AirPlay option in the menu bar.
If you can not see the AirPlay icon in the menu bar, you can enable it by going to System Preferences> Show and checking the Show Mirroring Options In option Menu Bar, if available.
Now click on the "AirPlay" button in the menu bar. Select your iPad here.
And that was it's. The Sidecar feature is now enabled and your iPad can now be used as an external display. You can now drag and drop windows from the screen of your Mac to the iPad.
Alternatively, you can go to System Preferences> Sidecar, and then click the Select Device drop-down menu and select your iPad from the list. Sidecar should now be running on your iPad.
Using and Customizing Sidecar
Although the iPad can be easily used as a secondary monitor, there are some special controls in macOS to use Improve usability.
First, you can switch to mirroring mode to control the Mac from the iPad. This can be useful if you are staying in the room but not sitting at the computer.
Click on the "Sidecar" button in the menu bar after the iPad has been connected. Then click on "Mirror built-in retina display".
The user interface of the sidecar on the iPad is quite simple. You can see a sidebar on the right and a virtual touch bar on the bottom (even if your Mac does not support the touch bar).
Top on sidebar You can see options for showing or hiding the menu bar and dock so you can enable full-screen mode on Mac.
In the middle you will find the modifier buttons: Command, Option, Control and Shift. You can tap a key twice to lock it.
Below are the Undo, Keyboard, and Disconnect options.
The Keyboard button invokes the iPadOS 'compact floating keyboard, which supports gesture input. The Disconnect button lets you exit the sidecar connection.
You can also customize the Sidecar UI that resides on the iPad. Go to System Preferences> Sidecar on your Mac.
From here, use the drop-down menu next to "Show Sidebar" to move the sidebar from left to right. You can also move the touch bar up or down from the Show Touchbar option.
You can also disable Show Sidebar and Show Touchbar options to disable both items.
If you're an avid Apple Pencil user, you can also check the "Double-tapping on Apple Pencil Enable" option to make the double-tapping gesture a right-click. Option to use on the Mac.
To disconnect from the sidecar, select the "Disconnect" button in the right or bottom left corner (depending on your settings) on the iPad screen.
Alternatively, you can go to the AirPlay menu on your Mac's menu bar and click the "Disconnect" button.