The iPhone Duo unlocks with Touch ID built into the side button, not Face ID. According to Apple’s tech specs, the sensor works whether the phone is open or closed, supports multiple fingers and can be paired with unlock with Apple Watch. The iPhone 18 Pro and 18 Pro Max, announced the same day, keep Face ID.
A Touch ID side button was one of the longest-running predictions in our pre-keynote iPhone Duo preview, and it is now confirmed. Apple has not said whether the under-display camera on the inner display can perform face authentication; per the tech specs it does not, and Touch ID is the only biometric on the phone.
How Touch ID works on the iPhone Duo open and closed
The side button sits on the titanium frame, so it is in the same place whether you are using the 5.4-inch outer display or the 7.6-inch inner one. Closed, the Duo unlocks like a slab phone with a side-button sensor: rest a registered finger and the outer display unlocks. Open, the same button is still on the frame, and the same fingers work.
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The multiple-fingers support matters more here than on a slab phone, because the Duo is held two different ways. Registering a thumb for closed use and an index finger for open use covers both grips without changing hands.
- Works with the phone open or closed
- Multiple fingers can be enrolled
- Unlock with Apple Watch is supported
- Handles Apple Pay, app sign-ins and password autofill as on other Touch ID devices
- No Face ID: the inner under-display camera and the 12MP outer camera are for FaceTime and photos, not authentication
Why the iPhone Duo does not have Face ID
Apple has not explained the choice, so this is our reading of the hardware. Face ID on the iPhone 18 Pro lives in the Dynamic Island on a single display. The Duo has two displays, and its inner camera sits under the display at f/1.8 for 1080p FaceTime, which Apple lists as a camera rather than a depth system.
A biometric that has to work in both states without duplicating hardware on both screens points to a button on the frame, and Apple has built the Duo around buttons: alongside the Touch ID side button, the press release lists a Camera Control button with a Siri Camera mode.
Touch ID vs Face ID: iPhone Duo and iPhone 18 Pro compared
| iPhone Duo | iPhone 18 Pro | |
|---|---|---|
| Biometric | Touch ID in the side button | Face ID |
| Works with the phone closed | Yes | Not applicable |
| Multiple fingers | Yes | Not applicable |
| Unlock with Apple Watch | Yes | Apple has not said |
| Front camera | 12MP Center Stage (outer), under-display FaceTime (inner) | No announced changes from the 17 Pro |
| Starting price | $1,999 | $1,199 |
Apple’s tech specs list no Face ID features for the Duo. Apple has not published anything about a future Face ID option for the foldable, and the iPhone 18 Pro remains the choice for anyone who wants face unlock.
The iPhone Duo goes on sale Friday, October 23, with pre-orders from Friday, October 16 at 5 a.m. PT. Our iPhone 18 Pro vs iPhone Duo comparison covers the other differences between the two phones.
