Checkmate

Checkmate lets you see your compatibility with anyone in seconds. Scan your friend, and see the long-term odds for the two of you, drawn from nearly a decade of relationship science research. People add all of their friends: “it’s on sight” one student put it, of the social norms that developed around the app. “If I recognize the face or the name, I add them.”

It went viral across colleges in spring of 2023. PayPal was famous for growing 7% per day. Checkmate grew 15% day over day.

A new and improved version, rolling out across schools in autumn 2026, adds relationship reports, your top 10 at your school, and more.