It was subsequently restricted to identify only people recognized as Facebook friends of the app user , and they used the app on their friends only after that change was made, they said.
A Facebook spokesperson denied that the app could ever identify strangers who didn't work at Facebook, saying that it was able to recognize only the faces of Facebook employees and of Facebook friends of the user who had enabled the social network's facial-recognition system on their accounts.
When pointed at someone, it would take about three to five seconds to recognize them, and then displayed their Facebook name and profile picture.
In September, Facebook said it would change to make facial recognition an opt-in feature, rather than assuming by default that users consent to having their faces scanned.
The existence of the experimental app, which has not been previously reported, highlights Facebook's willingness to experiment with technologies with major societal implications.
A Facebook spokesperson said the company routinely builds experimental apps internally, and that the facial-recognition app has since been discontinued.
The experimental app was developed at a time when Facebook was under pressure from then rapidly growing rival Snapchat and its comparatively advanced face-tracking technology and filters.
Original article