Correlating users who "like" a page with users of an app

Question

I have a page that links to my app. and this page has an increasing number of "likes".

We want to know how many of the FB users who have "liked" our page have authorized our app.

Per Querying Users who 'like' my Facebook Page, it doesn't appear that I can get the list of "likers" of my page in order to correlate the FB ids against my user base for the app.

Two questions:

1) Is there an existing Insights metric that I should be using to get this information? This does seem like a special kind of "conversion" (from page - liker to app - user).

2) The only other option I see is scraping the output of

https://www.facebook.com/browse?type=page_fans&page_id=PAGE_ID

which some have suggested violates the FB TOS (why is that, btw?). Does anyone have any other suggestions?

3) Upon further reflection, it occurs to me that I can come at this problem from the app instead. I should be able to get likes for my app users and see if my page is among them. Can anyone verify if this will work?

Many thanks, Wes

Answer 1

No, you'd need to manually calculate this by using the user's access token when they're using your app to see if they like the page - Facebook's API will not give you a list of users of your app or a list of likers of a page