The "Who Unfollowed Me on Instagram | Facebook" app is a free social and communication application developed by Nicer App. The app allows users to track their followers on Instagram and friends on Facebook. Users can determine who unfollowed them, who unfriended them, and who visited their profile recently. The Pro package offers additional features such as analyzing the personalities of Instagram/Facebook users, and customizing notifications that notify you when someone unfollows/unfriends you.

It is important to note that friend lists exist only on the user's mobile device, and data on Instagram/Facebook will never be shared. The app initializes data the first time you visit and then compares it with later dates to see who unfollowed/unfriended you on that social network. However, it cannot show who unfollowed/unfriended you before it was installed, and you need to wait for the next time to check to know who unfollowed you on Instagram or Facebook (if there are any).