> You're supposed to keep offline backup keys. Any sort of synchronization feature adds a ton of attack surface. I find that a terrible design decision, becaus

> You're supposed to keep offline backup keys. Any sort of synchronization feature adds a ton of attack surface. I find that a terrible design decision, because now every website has to implement their own backup code flow. PayPal, for example, is one of the most critical applications when talking about authentication, and while they support 2FA they don't give you any backup codes at all: https://www.paypal-community.com/t5/My-Account/Backup-codes/td-p/1812619 https://www.paypal-community.com/t5/My-Account/Backup-codes/... Now I cannot synchronize devices, I'm hosed if I ever lose my phone, and I'm still relying on PayPal customer support to do a proper out-of-band authentication. The worst of both worlds.