Apple’s iPhone Duo uses Touch ID in the side button instead of Face ID, giving the foldable phone one authentication method that works whether the device is open or closed. MacRumors reported the detail on September 10 after Apple published the phone’s product information.
Apple’s official announcement says the sensor is integrated into the side button. That placement lets a user authenticate without reaching for a separate Home button, which has not been part of recent iPhone designs. It also suits a phone that changes physical shape during normal use.
MacRumors said the side-button sensor can unlock the Duo in either position. The report also noted that an Apple Watch can be used to unlock the phone, giving owners a second hands-free option when the watch and iPhone are configured to work together.
The decision separates the Duo from the iPhone 18 Pro models, which retain Face ID. Apple’s product pages describe the Duo as a foldable device with a 7.6-inch inner display and a 5.4-inch outer display. A single side control therefore has to remain reachable in both configurations.
Touch ID is not a new technology for Apple. The company already uses side-button fingerprint sensors on several iPad models. The iPhone Duo brings that approach to an iPhone for the first time since the third-generation iPhone SE, released in 2022.
Apple says the Duo has a titanium frame, Ceramic Shield protection and an IP68 rating. Those specifications explain the phone’s hardware design, but they do not change the biometric requirement: owners will use a fingerprint, passcode or Apple Watch rather than Face ID.
Preorders for iPhone Duo begin October 16, and Apple says availability starts October 23. Until the device reaches customers, independent testing will show how quickly the side sensor works with the phone folded, open and used with a case.
