Since the launch of the iPhone 5s and Touch ID, there’s always been some precautionary measures in place with Apple’s fingerprint sensor. For example, when the phone is rebooted or hasn’t been unlocked in 48 hours, the phone will ask to enter the passcode to re-enable Touch ID. Earlier this month, Apple added more precautionary measures to their list.
According to the document, you’ll be asked to enter the passcode when one of five circumstances are met. For most people, none of these are actually met. However, Apple has added a sixth bullet point that may solve this mystery.
The new bullet point is bolded below (via MacWorld)…
The passcode can always be used instead of Touch ID, and it’s still required under the following circumstances:
- The device has just been turned on or restarted.
- The device has not been unlocked for more than 48 hours.
- The passcode has not been used to unlock the device in the last six days and TouchID has not unlocked the device in the last eight hours.
- The device has received a remote lock command.
- After five unsuccessful attempts to match a fingerprint.
- When setting up or enrolling new fingers with Touch ID.
According to the bullet point, your device must not’ve been unlocked within the last six days and has not been unlocked with Touch ID within the last 8 hours. The keyword is “and”. If you use Touch ID to unlock your device everyday, the passcode is never used.
Therefore, if you lock your phone for the night and sleep more than 8 hours, your device will ask you for the passcode because it’s been over 8 hours, and it’s been six days since you’ve unlocked your device with the passcode.
It’s worth noting that the 8-hour window will reset itself every time you’ve unlocked your device with Touch ID. And the six day window will reset itself every time you’ve entered your passcode.