iPhone Duo has no Face ID, so unlocking by fingerprint happens at the side button, where Touch ID works the same way whether the phone is folded shut or open. Apple dropped Face ID for the foldable, and the trade-off is a short pause between touching the sensor and landing on the Home Screen.
Three settings cut that wait down, and each one suits a different habit.
Turning Off Rest Finger to Open Removes the Pause
With Rest Finger to Open on, resting a registered finger on the side button unlocks the phone and takes you straight to the Home Screen. The short wait before that happens gives you time to glance at your notifications first, and turning the setting off makes the phone unlock immediately.
Go to Settings > Touch ID & Passcode and switch off Rest Finger to Open. The same toggle also lives under Settings > Accessibility > Side Button. After that, Touch ID unlocks the phone and you swipe up from the Lock Screen when you are ready to open it.
The right choice depends on how you pick up your phone. If you tap the screen, read your notifications and then decide whether to open anything, turn it off. If you swipe straight to the Home Screen every time, leave it on, since the pause costs you nothing.
Registering Extra Fingers Lets the Phone Open as You Grip It
A fingerprint trick can open the phone as you pick it up. Register the finger that already rests on the side button when you grip the Duo, so the sensor reads it without a deliberate touch. It needs Rest Finger to Open switched on, because the grip has to open the phone and not only unlock it.
Open Settings > Touch ID & Passcode > Add a Fingerprint and hold the phone the way you normally do while you scan. Add the fingers that land on the sensor when the Duo is folded and the ones that land there when it is open. Turning Rest Finger to Open off removes the pause but ends this trick, because the phone then waits for a swipe.
Unlock with Apple Watch Skips the Sensor Entirely
iPhone Duo also supports Apple Watch unlock, a feature Apple carried over from the Mac. With the option on, the wait for a fingerprint disappears for anyone who wears a watch all day.
- Open Settings on iPhone Duo and tap Touch ID & Passcode.
- Turn on Unlock with Apple Watch for your watch.
- Keep the Apple Watch on your wrist and unlocked when you pick up the phone.
Touch ID stays available either way, so switching the watch option on takes nothing away. Unlock with Apple Watch only works while the watch is on your wrist and unlocked.
