The hinge of the foldable smartphone has gained a new use. A free app called “DuoBook: Pocket Mac” has begun distribution on the App Store, allowing users to fold Apple’s first foldable device, the iPhone Duo, in half and stand it up to operate it like a macOS-powered laptop.
When the app is launched and the device is propped half-open like a book, the Mac screen from home or the office appears on the top half, while a keyboard and trackpad appear on the bottom half. The layout changes according to the hinge angle, and when opened flat, the display area and trackpad expand.
The key layout is the same as Mac laptops, with the top row featuring screen brightness adjustment, Mission Control, Spotlight, voice input, and more. Modifier keys can be toggled so that a single tap applies them to only the next key, while a double tap locks them. Pressing the Touch ID key locks the Mac, and key-press sounds and haptics are also reproduced. Version 1.1 added Touch Bar display support.
The top-row display links to the app currently in use on the Mac. Safari shows back and forward buttons, Music shows play and skip controls, and Keynote shows slide advance controls.
To connect from outside the home, users install the free “DuoBook Host” on their Mac, enable “Access from anywhere,” and complete a one-time pairing on their home Wi-Fi. With a compatible router, most settings are completed automatically, and the Mac’s address is stored in the user’s own iCloud. Connection verification only requires matching a six-digit code displayed on both screens.
After connecting, users can listen to the Mac’s audio on the iPhone, paste text copied on the Mac onto the iPhone, and send photos and files to the Mac’s Downloads folder. With an iPhone Duo and a mobile battery, there will likely be more situations where users no longer need to carry a laptop or tablet.
However, macOS is not actually running on the iPhone. The mechanism is purely remote connection, transmitting the screen of a Mac running at home or the office and sending back key inputs and pointer movements. To use it while out, the Mac must be left powered on, but version 1.1 added a feature to remotely wake a sleeping Mac.
Requirements are: installing DuoBook Host on a Mac running macOS 14 Sonoma or later, and granting screen recording and accessibility permissions. In Japan, the iPhone Duo starts at ¥364,800 (approximately $2,300).
Interest in foldable devices also appears high in the South Korean market. According to South Korean media reports, the iPhone Duo went on sale in South Korea on the 23rd of last month, and initial inventory sold out on the first day of preorders. The outer screen when folded measures 5.4 inches, while the inner screen when opened measures 7.6 inches, and the center crease is said to be almost invisible from the front. This is thanks to a hinge composed of more than 100 parts and a nano-texture matte finish that suppresses light reflection.
The thickness when open is 5.2mm, which Apple describes as the thinnest of any iPhone to date. The frame is made of titanium, and the chip is the same “A20 Pro” as the iPhone18 Pro. Batteries are distributed on both sides of the body, with video playback lasting up to 44 hours on the outer screen and up to 31 hours on the inner screen. The rear features 48-megapixel wide-angle and ultra-wide-angle cameras, while the inner screen’s selfie camera is hidden beneath the display. Unlocking is handled by fingerprint authentication (Touch ID) on the side button.
The device also supports split-screen mode, dividing the display at the crease to show separate apps on the left and right. In the always-on display feature showing the clock, calendar, and weather, the screen switches to a dim red color when the surroundings darken, designed not to interfere with sleep. It also includes features such as displaying video calls on the outer screen and automatically triggering the shutter when propped half-open.
Integration between Apple products is another hallmark. It supports unlocking via Apple Watch and the use of MagSafe chargers, and the Apple Pencil (USB-C) for iPad can be used to write on both the inner and outer screens. This marks the first time an iPhone supports Apple Pencil.
There are challenges as well. In South Korea, the 256GB model is priced at ₩3.29 million (approximately $2,500) and the 2TB model at ₩5.09 million (approximately $3,800), making it as expensive as in Japan. Critics also point out that the on-screen control menu is concentrated on the right side, making left-handed operation difficult, and that some apps that have not been optimized display in small windows in the center of the opened screen, failing to take full advantage of the large display.
The emergence of peripheral apps like DuoBook can be seen as a move to present new uses for high-priced foldable devices. In a foldable market where competition over device sales continues, the ability to leverage existing Mac assets while on the go is likely to appeal to users who own multiple Apple products. That said, by its nature as a remote connection, it still depends on the communications environment and the operating status of the Mac at home.