Hidden iOS 18.1 feature makes iPhones restart automatically

At the end of last week, a report from 404 Media was published, based on a memo from law enforcement officials in the US.

According to the report, the police are having problems with iPhones with iOS 18: they switch off uncontrollably and require the corresponding passcode after restarting, which makes it significantly more difficult for authorities to access the data on the device.

Based on these reports, the developer scene spent the past weekend looking for confirmation or an explanation for this phenomenon and finally found something.

Jiska Classen, an engineer at the Hasso Plattner Institute in Potsdam, Germany, explained the differences between iOS 18 and iOS 18.1 in an post on X/Twitter. It appears that iOS 18.1 includes new lines of code with the “Inactivity Reboot” feature.

Essentially, this means that a system timer will be enabled every time the iPhone is locked. If the iPhone is not unlocked for a certain period of time – the researchers assume four days, or 96 hours – the iPhone will restart and prompt you to enter the current passcode. The restart after inactivity is apparently only linked to the time of the last unlock, and not to other conditions such as connection to nearby devices.

It is not yet clear whether the previous report from 404 Media and the code found in iOS 18.1 are related; it could just be a coincidence.

Apple has not yet provided an explanation

Apart from that, we would have liked Apple not to hide such features from its users and hoped that no one would know about the change. After all, this is a basic function of the iPhone and users can assume a defect if they notice that their iPhone seems to turn off sporadically.

As for the question of whether someone leaves their iPhone unused for more than four days: there are plenty of business iPhones around that are only used for business communications during the week, a four-day break is not unusual even on the many long weekends, let alone only holidays.