The dating app startup founded by Sean Rad and Justin Mateen was Tinder.
Tinder began in 2012 inside Hatch Labs, a startup incubator in West Hollywood. Rad initially presented the idea under the working name Matchbox during a hackathon, and the early team developed it as a mobile dating service built around photo profiles and mutual interest. Justin Mateen joined as a co-founder and later became Tinder’s chief marketing officer.
The app was soft-launched in September 2012, first gaining traction on college campuses. Its signature swipe interaction evolved from an earlier click-based design and helped make mobile dating feel fast and game-like. Tinder is often described as having only two founders, but its early founding group also included figures such as Whitney Wolfe Herd and Jonathan Badeen. That broader history does not change the canonical quiz answer: the app is Tinder.