Duolingo

Duolingo is a language-learning company that styles itself as a "global school" built technology-first from day one . It went public on Nasdaq in July 2021, a moment co-founder and CTO Severin Hacker described as the highlight of his career . The company runs on what it calls the "Green Machine" — a system of relentless A/B testing and iterative experiments rather than any single feature, though its streak mechanic has been optimized over 300 times since its debut .

The product's stickiness comes from treating gamification as core architecture, not an add-on: streaks, XP points, and habit formation are the main event, with Duolingo's own research showing users would otherwise simply scroll social media rather than switch to competing language apps . As of late 2025, monthly active users stood at roughly 130 million, with a stated goal of reaching one billion learners . Revenue comes from tiered subscriptions — Free, Super, and Max — with premium AI features like "Video Call with Lily" reserved for the top tier due to per-use API costs .

Duolingo's 2025 pivot to "AI-First," announced by CEO Luis von Ahn in an April internal memo, accelerated course production dramatically: 148 new courses in one year versus 100 across the prior twelve . The move also triggered a subscriber backlash, with users posting cancellation screenshots and deleting apps holding thousand-day streaks — a tension the company navigated to "come back as winners" rather than be seen as AI losers, in Hacker's framing .