Apple’s first foldable iPhone Duo authenticates through a Touch ID sensor built directly into the side button, and it works whether the phone is open or closed.
The sensor supports multiple fingerprints, so you can register one finger for closed use and another for when the phone is unfolded. Apple Watch unlock is also available, giving Duo owners a hands-free option that skips the button press entirely.
Why iPhone Duo Has Touch ID and Not Face ID
A normal iPhone has one front and one obvious spot for a TrueDepth camera. iPhone Duo has two: a 5.4-inch outer display and a 7.6-inch inner display, and each one becomes the “front” depending on whether the phone is folded or open.
A single Face ID system tied to one screen would leave the phone with no facial unlock at all in the other state. Building TrueDepth into both displays would fix that, but it also means duplicate hardware, added cost, and less room inside a body that’s only 5.2mm thick when unfolded.
iPhone Duo already has to fit two displays, a folding hinge, two separate batteries, the A20 Pro chip, and a custom vapor chamber into that space. Apple hasn’t published an official explanation for the decision, so this reasoning comes down to the physical constraints of the hardware itself.
Neither Camera on iPhone Duo Does Face Recognition
The inner display hides a FaceTime camera beneath the screen, shooting 1080p video at f/1.8. Apple lists it as a standard camera, not a depth-sensing system.
The outer display carries its own 12MP Center Stage camera at f/2.2 with Retina Flash, built for video calls and photos when the phone is closed. Center Stage keeps a subject framed as they move, but it doesn’t recognize faces for authentication. Touch ID is the only biometric system on the entire device.
iPhone 18 Pro Max Keeps Face ID the Same Day Duo Loses It
Apple announced iPhone 18 Pro and iPhone 18 Pro Max alongside iPhone Duo, and both Pro models keep Face ID in the Dynamic Island exactly as before. The split means Apple is running two different authentication systems across its current flagship lineup at the same time.
| Feature | iPhone Duo | iPhone 18 Pro Max |
|---|---|---|
| Biometric system | Touch ID (side button) | Face ID |
| Works closed and open | Yes | N/A |
| Apple Watch unlock | Yes | Yes |
| Starting price | $1,999 (256GB) | Varies by config |
iPhone Duo Pre-Orders Open October 16 at $1,999
Pre-orders begin Friday, October 16 at 5:00 a.m. Pacific Time, with the phone reaching customers on Friday, October 23. Pricing starts at $1,999 for the 256GB model, or $83.29 a month over 24 months.
