Google announced its Pixel 4 series of handsets earlier this week, and one thing that's different this time around is that there's no fingerprint sensor on the back. Instead, they use a new face unlock feature. Unfortunately, it turns out that with face unlock, you don't actually have to be looking at the phone.
On Google's face unlock support page, the company confirmed that your Pixel 4 can be "unlocked by someone else if it’s held up to your face, even if your eyes are closed". The firm also noted that looking at the phone can unlock it when you don't mean to, and it can be unlocked by someone that "looks a lot like you".
The only other mainstream flagship smartphones that have facial recognition and no fingerprint sensor are Apple's lineup of iPhones. And even when Apple's Face ID was first introduced with an iPhone X two years ago, it required not only that your eyes be open, but that you're actually looking at the device.
Sadly, there's no option to require your eyes to be open on the Pixel, although it wouldn't be surprising if Google adds that at some point. If you're worried about someone using your face to unlock your phone while you're sleeping, your only option is to turn off the feature completely.