Apple has unveiled its first foldable smartphone, the iPhone Duo, and is moving to support developers ahead of its official October launch.

Apple unveiled the iPhone Duo alongside the iPhone 18 Pro and Pro Max, Apple Watch Series 12 and Ultra 4, and AirPods 5 with improved noise cancellation at its Surprise and Shine event on Sept. 9 local time, IT outlet 9to5mac reported. The outlet said Apple opened a new developer page immediately after the announcement and began providing materials to help developers prepare apps for the iPhone Duo.

Apple published iPhone Duo assets on its Design Resources portal and will hold an iPhone Duo Group Lab over two days on Sept. 16 and 17. It will also run two Q&A sessions each on Sept. 23 in the photo and camera, SwiftUI and UIKit categories, split across time slots. iPhone Duo workshops will also begin around the world this month. The hands-on sessions let developers work directly on their apps and test "resizability" tailored to all screen sizes. The developer page also listed tools and documents to be released, including Xcode 27.1 beta, "Designing for iPhone Duo" and "Preparing your iPhone Duo app."

■ App compatibility divided into three stages

Apple also gave a detailed explanation of how third-party apps are displayed on the iPhone Duo's large screen. Zac Hall (잭 홀), a reporter at 9to5mac, cited a developer Tech Talk video on Sept. 9 local time as saying compatibility modes are split based on three versions: iOS26, iOS27.0 and iOS27.1.

Apps built for versions earlier than iOS27.0 run in a basic compatibility mode, showing only a single screen within a narrow safe area against a black background. Apps updated for iOS27 use much of the Duo's wider display, but empty space remains. In October, when the iPhone Duo is released, Apple will also roll out iOS27.1, and only apps built for that version can use the entire screen in full compatibility mode. Many Apple apps and third-party apps seeking the best experience are expected to choose this approach.

Apple appears to be accelerating efforts to prepare its developer ecosystem as it enters the foldable market. It is unusual for the company to roll out group labs, workshops and detailed compatibility guides all at once, and this is seen as an attempt to boost app optimisation by the October launch.