system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How does face scanning work with twins?
gpt
There are different methods of "face scanning," but they all rely on nuances in physical appearance. (More advanced methods use the topography of the face and not just a comparison between images.) They can't distinguish between two different people that look essentially the same, anymore than a lock distinguishes between two people that have subtly different copies of a key.

The accuracy of particular methods, and products that implement them, varies. Identical twins also vary in how alike they are--the environment does have an influence on how you look, not just your genes. But it's safe to say there's a significant potential for a scanner to fail to distinguish between identical twins.

Ideally, biometric markers should never be relied upon for authentication, because you can't change them if they are compromised. They should be more like a user name than a password. But they can strengthen security if implemented alongside a secure authentication method, such as passwords, a key card, etc.