iPhone Duo unlocks with Touch ID built into the side button, not Face ID, and Apple says it works with the phone open or closed, accepts multiple fingers, and can be paired with Unlock with Apple Watch. Setting it up means enrolling each finger you will use in both positions, then turning on the Apple Watch option as a backup.
Apple has not published a Duo-specific setup guide, so the steps below follow Apple’s published description of the feature and may differ slightly once iPhone Duo ships with iOS 27.1 on October 23. Hardware details are from Apple’s product page, tech specs and press release.
Key facts about Touch ID on iPhone Duo
| Item | Detail (Apple’s product page and tech specs) |
|---|---|
| Biometric | Touch ID in the side button; no Face ID |
| Works when | Phone open or closed |
| Fingers | Multiple fingers can be enrolled |
| Apple Watch | Unlock with Apple Watch supported |
| Inner camera | Under-display FaceTime camera; does not support Face ID |
| Closed size | 84.1 mm wide, 117.8 mm tall, 11.3 mm thick, 254 g |
| Open size | 164.6 mm wide, 117.8 mm tall, 5.2 mm thick |
| Launch | Pre-orders October 16, available October 23 from $1,999 |
Why iPhone Duo uses Touch ID instead of Face ID
Apple’s tech specs list Touch ID in the side button as the Duo’s biometric and no Face ID. The inner display’s FaceTime camera sits under the screen and does not support Face ID, and the outer display’s 12MP Center Stage camera is not listed as a Face ID camera either.
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The practical result is one sensor that works in both of the phone’s states. Apple says Touch ID works open or closed, so the same press of the side button unlocks the 5.4-inch outer display when the Duo is shut and the 7.6-inch inner display when it is open. That is a different daily routine from the iPhone 18 Pro, which keeps Face ID, as our iPhone 18 Pro official guide explains.
How to set up Touch ID with multiple fingers on iPhone Duo
Apple has not published where the Duo’s Touch ID settings live. On Apple’s other Touch ID iPhones the option sits in Settings under Touch ID and Passcode, and Apple’s Duo description gives no reason to expect a different location, but treat that as a guide until iOS 27.1 ships.
- Open Settings and find the Touch ID and Passcode section. Set a passcode if you have not already; Touch ID requires one.
- Choose to add a fingerprint and rest the finger you use most on the side button, lifting and repositioning as the phone asks, until the print is captured.
- Add a second finger. Apple says the Duo supports multiple fingers, so enroll the thumb or finger you use when the phone is closed as well as the one you use when it is open.
- Choose what Touch ID can do. Apple has not detailed which options, such as purchases or password autofill, the Duo offers.
- Test in both states. Lock the phone, press the side button while it is closed, then open it and press again. Apple says both should unlock.
How to turn on Unlock with Apple Watch on iPhone Duo
Apple lists Unlock with Apple Watch for the Duo. Apple has not said which Apple Watch models or watchOS versions it requires on the Duo, so check the option once you have the phone. Our Apple Watch Series 12 guide covers the current watches.
- Pair your Apple Watch with the Duo and make sure the watch has a passcode set and is on your wrist and unlocked.
- In the Duo’s Touch ID and Passcode settings, find the Unlock with Apple Watch option and turn it on for your watch.
- Confirm on the watch if prompted.
- With the option on, the Duo can unlock when Touch ID does not succeed and your unlocked watch is nearby. Apple has not described the exact conditions on the Duo.
If Touch ID does not work on iPhone Duo
- Dry your finger and the side button. Apple rates the Duo IP68 to 6 meters for 30 minutes, but a wet or dirty sensor still reads poorly.
- Enroll the finger again in the position you actually use. A thumb on the closed phone lands differently from a finger on the open phone.
- Check that Unlock with Apple Watch is on if you rely on it, and that the watch is unlocked and on your wrist.
- Enter your passcode. Touch ID falls back to the passcode, and Apple has not said how many failed attempts the Duo allows before it requires one.
| Feature | iPhone Duo | iPhone 18 Pro |
|---|---|---|
| Biometric | Touch ID in the side button | Face ID |
| Works with the phone closed | Yes, per Apple | Not applicable |
| Front camera | 12MP outer Center Stage; under-display inner camera | 18MP Center Stage |
| Unlock with Apple Watch | Yes, per Apple | Apple has not said |
| Price | From $1,999 | From $1,199 |
What Apple has not said
- How many fingerprints the Duo can store.
- Which Apple Watch models and watchOS versions Unlock with Apple Watch requires on the Duo.
- Whether Touch ID handles Apple Pay, App Store purchases and password autofill on the Duo.
- Whether Touch ID behaves differently in the posed positions Apple describes.
- Whether a future software update could add Face ID via the outer camera.
iPhone Duo pre-orders open Friday, October 16 at 5 a.m. PT, with availability on Friday, October 23 from $1,999 for 256GB, or $83.29 a month over 24 months, per Apple’s press release. Our iPhone Duo official guide has the full spec sheet, and our iPhone Duo vs iPhone 18 Pro Max comparison weighs Touch ID against Face ID alongside every other difference.
