Apple debuts the iPhone Duo, its first foldable, priced at $1,999

Apple ( AAPL ) debuted its first foldable iPhone on Wednesday, marking the largest overhaul of its smartphone design ever and creating a new revenue opportunity for the tech giant.

Called the iPhone Duo and starting at $1,999, the device features a passport-like design that opens and closes like a book.

Up front, the Duo sports a 5.4-inch display. Open the phone to reveal a massive 7.6-inch display that's ideal for watching movies, playing games, doing work, and multitasking.

When unfolded, Apple said the Duo is its thinnest iPhone yet.

Changing the phone's orientation automatically adjusts how apps appear, so if you fold it in half while watching a video, the top half will show the content, and the lower half will show the controls.

In Zoom, the top portion of the screen will show a shared view of your call, while the bottom will show the call's participants.

To limit the crease seen on other foldables, Apple said it created a custom nano-texture finish and used multilayer lamination to help with durability.

Inside, the iPhone Duo gets Apple's A20 Pro chip that, when combined with a new cooling system, gives the foldable 35% higher sustained performance than the iPhone 17 Pro.

As for battery life, Apple said the Duo will offer 31 hours of video playback on a charge and 44 hours when you're using the front screen. When using both screens equally, you should get 24 hours of usage.

The iPhone Duo also gets two high-powered 48-megapixel cameras on the back — one for wide-angle shots and another for ultrawide. There's also a cutout for the Center Stage camera on the front screen and an under-display FaceTime camera for the main panel.

A new Duo Preview mode lets you open the camera and use the inner screen as a viewfinder, while the front screen shows your subject a preview of the shot, allowing them to give you "welcome" notes.

The iPhone Duo is available for preorder on Oct. 16 and goes on sale Oct. 23.

Email Daniel Howley at dhowley@yahoofinance.com. Follow him on Twitter at @DanielHowley .