Apple's new Sidecar app lets you connect an iPad to your Mac for extra screen space. It works both wired and wirelessly, and supports the Apple Pencil as an input device for the Mac.
And for Mac apps with Touch Bar support, the controls appear at the bottom of your iPad screen — even if your Mac doesn't have a Touch Bar.
In other words, the iPad Touch Bar mirrors the MacBook Pro's Touch Bar on a model with a Touch Bar, and when used with a MacBook Pro that doesn't have a Touch Bar, it lets you tap into functionality that would otherwise be unavailable.
The implementation will be familiar to users of Duet Display, which was first to offer Touch Bar support on a connected tablet's screen.
Since its introduction, the Touch Bar has divided users – some find the functionality useful, while others prefer their MacBook Pro to have a full set of physical function keys instead.
The Sidecar app is compatible with 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, and 2019 Mac Pro.