Web users are increasingly presented with multiple login options, including password-based login and common web single sign-on (SSO) login options such as "Login with Google" and "Login with Facebook". There has been little focus in previous studies on how users choose from a list of login options and how to better inform users about privacy issues in web SSO systems. In this paper, we conducted a 200-participant study to understand factors that influence participants' login decisions, and how they are affected by displaying permission differences across login options; permissions in SSO result in release of user personal information to third-party web sites through SSO identity providers. We compare and report on login decisions made by participants before and after viewing permission-related information, examine self-reported responses for reasons related to their login decisions, and report on the factors that motivated their choices. We find that usability preferences and inertia (habituation) were among the dominant factors influencing login decisions. After participants viewed permission-related information, many prioritised privacy over other factors, changing their login decisions to more privacy-friendly alternatives. Displaying permission-related information also influenced some participants to make tradeoffs between privacy and usability preferences.
