Overview: Our iOS app supports Face ID for logging in and out of the app. Unfortunately, Apple only allows up to 2 faces to be stored on an iPhone, so for a large workforce sharing a device our other Facial Recognition solution is required. However, if your employees use their own devices, they are free to use Face ID.
You can use Face ID on the following devices:
iPhone Models
iPhone XS Max
iPhone XS
iPhone XR
iPhone X
iPad Models
iPad Pro 12.9-inch (3rd generation)
iPad Pro 11-inch
*source: https://support.apple.com/en-us/HT209183
To use 2 faces on the device you will need iOS 12 or later. Prior iOS versions only supported 1 face.
How-To Add Multiple Users to Face ID
If you want to add a new user to Face ID on your iPhone, the steps are pretty straightforward.
Here is what you will need to do:
Open Settings
Scroll and select Face ID & Passcode
Enter Passcode
Tap Set up an Alternative Appearance
After you have selected Set up an Alternative Appearance, you or that one other person need to follow the same process as you did the first time. Apple instructs you what to do, but it involves moving your head around in circles.
But once complete, you have two appearances ready for Face ID to use.
FAQ
Q: Can I Delete or Change An Alternate Appearance for Face ID?
A: Once you enter an alternate appearance, there’s no option to delete it. Instead, you need to Reset Face ID to change your alternate appearance. Unfortunately, that also means you must re-enter all Face IDs. When you tap Reset Face ID, your device removes and deletes all your Face ID data–including your original Face ID and your alternate appearance.