ANONYMOUS SINGLE SIGN-ON TO THIRD-PARTY SYSTEMS

An online system receives from a third-party application on a client device, an anonymous login request to anonymously log a user of the online system into a third-party system associated with the third-party application. Responsive to receiving the anonymous login request, the online system generates a permissions user interface (UI) that provides an interface component including an option for the user to anonymously log into the third-party system using the user's login information for the online system. The online system provides the permissions UI to the client device, and receives permissions information from the client device. The online system generates an anonymous identifier that allows the user to login to the third-party system. The online system provides the anonymous identifier to the third-party application to allow anonymous login of the user into the third-party system in accordance with the permissions information.