Duolingo makes a phone app for learning languages through short, game-like lessons. It offers over 250 language courses, plus courses in math, music and chess. Anyone can use the app for free; free users see ads after lessons, while paying subscribers get no ads and extra features, some of them powered by AI. It also runs the Duolingo English Test, an online English exam that over 6,100 education programs accept for international student admissions.
At the end of 2025 it had more than 130 million monthly active users, and about 12.2 million of them paid for a subscription. Subscriptions are its main source of money, bringing in $873.4 million in 2025; ads, the English test and other sales brought in $164.1 million. Most payments come through Apple's and Google's app stores, and US customers made up 38% of revenue. It competes with other online and app-based language programs, classes and other offline ways of learning, and, in its newer subjects, with other math, music and chess learning products.
Duolingo was founded by Luis von Ahn and Severin Hacker, who met at Carnegie Mellon University. It had more than 900 employees at the end of 2025, more than 430 of them engineers.