Duolingo: On a "Streak"

In December 2024, Severin Hacker, Co-Founder and Chief Technology Officer of Duolingo, reflected on the remarkable evolution of the language-learning app he helped launch in 2011. As the #1 most downloaded education app in the world, Duolingo had over 100 million monthly active users, 8 million paid subscribers, and a market cap approaching $15 billion in late 2024. The company’s success stemmed from its gamified approach to learning, its use of adaptive AI technology, and its alignment of incentives: maintaining a streak on the app not only helped users master a language but also drove subscription growth and reduced costs for Duolingo. To date, Duolingo had focused almost exclusively on language learning with an estimated market size of $17 billion in 2020. As a technology-first company, Duolingo recognized the enormous potential of Gen AI to power innovative products, such as conversational language practice. However, Hacker envisioned an even broader future in which AI could transform the app into a comprehensive AI-powered educational ecosystem that covered many subjects beyond language, allowing the company to tap into the $56 billion ed-tech market. The company had recently started to explore this direction by adding new subjects, such as math and music. This product line diversification raised several strategic questions: Did Duolingo have the brand license to extend into adjacent subjects? Which areas were the best fit for the app’s growth, and how quickly should they roll out? And what were the long-term benefits and risks to new subjects within the flagship app?