Implementation of Facebook SDK Connect from 2014.
https://developers.facebook.com/
JavaScript Libraries and Functions · JavaScript Library
Get access to data on 93,369 websites that are Facebook SDK 2014 Customers. We know of 59,549 live websites using Facebook SDK 2014 and an additional 33,820 sites that used Facebook SDK 2014 historically and 28,302 websites in the United States.
Get a list of 93,369 websites using Facebook SDK 2014 which includes location information, hosting data, contact details, 59,549 currently live websites and an additional 14,117 domains that redirect to sites in this list. 33,820 sites that used this technology previously and 28,302 websites in the United States currently using Facebook SDK 2014.