Apple's head of software also clarified about sunglasses and one very awkward moment during the launch event
If you squeeze the iPhone X it will stop people from stealing it, Apple has said.
The phone has security settings that stop the built-in facial recognition from being used if the two buttons on the side are press, according to head of software Craig Federighi. The revelation was part of an email the Apple executive sent to a developer, who asked a series of questions about the Face ID technology.
The emails reveal more about the technology, which won't be released to the public until 3 November and so has only really been discussed by Apple. Mr Federighi added to those concerns during the introduction event, when he went to use the facial recognition tools and the phone wouldn't actually let him in, leading to worries that they aren't as good as Apple had made them out to be.
But he said that problem was something that would never happened in real life, since it was shut down after a number of different people interacted with the phone to get it ready for the demo. "For those of us who have been living on the iPhone X over the last months this has never been a real problem," he wrote in the message to developer Keith Krimbel.
Perhaps most important of all, Mr Federighi attempted to calm people worried that the phone would be easy to steal. A number of people have voiced concern that someone stealing the phone could simply point it in the face of the person it was being stolen from, and then have access to everything on the iPhone.
"There are two mitigations" against such a thing happening, Mr Federighi said. "If you don't stare at the phone, it won't unlock.
"Also, if you grip the buttons on both sides of the phone when you hand it over, it will temporarily disable FaceID."
Mr Federighi also clarified whether the Face ID would continue to work when someone is wearing sunglasses. He said that it would do so "with most, but not all", because most sunglasses let enough infrared light through that the FaceID can still see the face of the person holding the phone.
"It's really amazing!" he wrote.
Apple said during the event that it would continue to work even if you grew a beard, changed your hair, or put on a scarf or a hat.