In March, Twitter said it would soon let you use a security key as your only two-factor authentication method, and on Wednesday, it announced that the feature was live on both mobile and web. Being able to use a security key as one of your two-factor authentication methods isn’t new, but now you can make it the only one if you want to. Physical security keys have advantages over other two-factor methods like an authenticator app or SMS because they don’t rely on a code that a bad actor could intercept.