COSMOPOLITAN - Jan 2 - Getting dating apps to reveal their matchmaking algorithms is like asking KFC to share its secret recipe. "Most apps use 'collaborative filtering,' which was first developed by Amazon," says tech expert Rhys Maddocks. He's the founder of JobSwipe, an app that allows job seekers to swipe their way through different potential roles in the hope of a mutual match. Collaborative filtering assumes if users buy the same product as someone else, they will also be interested in the other items they purchased. Some apps also use face-mapping, pinpointing physical features users have a preference for and then sifting those with similar features to the top. Others use language matching so when chatting about travel, food or fitness, users will be shown matches who have put similar things in their profiles. The dating apps know what times users are active and can tell which accounts are being used to make real-life connections. The goal is to put people who are very active on the app high in the stack.