I'm a big fan of Face ID on the iPhone X. It is a big improvement over the Touch ID fingerprint identification system on other iPhone models because, when it works, it provides security without any inconvenience at all. You are looking at your iPhone anyway when you pick it up to use it, and then Face ID unlocks the phone, almost as if you didn't even have a passcode at all. In an excellent recent article on the iPhone X, John Gruber of Daring Fireball described it this way:
Consider the aforementioned process of opening a notification from the lock screen. Touch ID adds an extra step, every time, even when it works perfectly. Face ID is not perfect — it’s true that I wind up either authenticating a second time or resorting to entering my PIN more often than with Touch ID — but it only adds these extra steps when it fails for some reason. When it works perfectly, which for me is the vast majority of the time, the effect is sublime. It really does feel like my iPhone has no passcode protecting it. That was never true for Touch ID. Touch ID feels like a better way to unlock your device. Face ID feels like your device isn’t even locked.
Unfortunately, as Gruber noted, the current generation of Face ID fails more often than Touch ID fails. Here is a tip I recently figured out (just by dumb luck) for dealing with Face ID when it does fail.
If Face ID fails on the Lock screen, you are presented with a keypad to type in a number of password. If you want to try Face ID again, I previously thought that the only way to to do was to press the cancel button and start all over again.
Here is a better way. If you turn your iPhone away from your face for just a second — so that the Face ID camera is looking at something else — and then you turn it back towards your face, I find that Face ID works the second time almost 100% of the time. This saves you the trouble of pressing that cancel button and starting over again. Just slightly rotate your wrist, turn it back, and you are done.
This also works with apps that use Face ID as an alternative to typing a username and password. If Face ID fails, you will see a message like this one with the option to tap an on-screen button to Try Face ID Again:
But you can ignore that button. Just turn the iPhone away from your face, then bring it back, and Face ID will see you without you having to touch the screen at all. You'll see the green happy face, and then the app will unlock.
Since I started using this method, the relatively rare instances in which Face ID fails have become far less annoying for me.