If you’re at all versed in today’s dating apps, there’s a good chance you’ve heard about Tinder. Tinder is a free, location-based dating app that allows people to see other users looking for a date or hook-up in their geographic vicinity. One of the most popular features of Tinder is that it allows users to swipe another user’s photo to the right if they’re interested in that user, or to the left if they’re not interested. Users can only contact one another if they both swipe right, indicating they both want to proceed. Tinder’s formula has worked, and the app has soared in popularity; by the end of 2015, it had more than 9.6 million active daily users and 25 million registered users.