What Is Sidecar?
Sidecar enables you to use your iPad as a second monitor for your mac, either via a wired connection or wirelessly. you can set it to the left or right of your main display and use it as you'd any other monitor, however that’s not all it can do.
Notably, Sidecar takes advantage of the iPad’s touchscreen. It even supports the Apple Pencil, which makes it a good addition if you’re a creative person wanting to expand your inventive choices. If you’re jealous of the touchscreen on Windows computers, this doesn’t get you all the method there, however, it’s a step closer.

What you need to Use Sidecar
To get started using Sidecar, you’ll need to have the right software system on each your mac and iPad. On the mac side, you need macOS 10.15 Catalina or later. However, not all Macs that can|that may} run Catalina will work with Sidecar.
For mac laptops, MacBook and MacBook Pro models from 2016 forward are supported. If you have got a MacBook Air, only the newer models from 2018 and onward work with Sidecar.
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https://stacktechhow.com/how-to-use-ipad-as-a-second-mac-monitor-with-sidecar/