Take the 2-minute tour ×  We are implementing a voting-system
inside an facebook app. The users are able to upload content and
vote the content of other users. We are aiming for a low entry-
barrier for users who only want to vote other users content. As
we want unique votes, we have to identify the users somehow. Is
it possible to identify users that did not grant permissions for
the app? The signed request does only contain statistic data for
the current user (country, locale, age-range) and no session. We
do not need any specific data of the user, just something unique
per user.  We are using an iframe-app.  share|improve this
question add comment  2 Answers  Basic authentication will give
you user ids -- probably the best way to uniquely identify a
Facebook user, although it adds friction.  Alternatively for a
very low barrier to entry you could use a Like Button and query
the Graph for number of votes. If you decide to use the like
button, and there is a prize based on the number of votes,
please make sur