Duolingo, Inc.

Duolingo uses gamification mechanics (streaks, leaderboards, achievement badges) combined with AI-driven adaptive learning to keep users engaged in daily language practice, scaling to hundreds of millions of users globally through a freemium mobile-first model. Its AI systems personalize exercise difficulty and review timing based on individual forgetting curves.

The Duolingo English Test offers an AI-graded, at-home alternative to traditional English proficiency exams, accepted by thousands of universities worldwide, providing a faster and cheaper option relevant to Vietnamese students applying abroad.

1. Gamified daily language practice
2. AI-driven adaptive exercise difficulty
3. Duolingo English Test (AI-graded, university-accepted)
4. Freemium mobile-first model
5. Multi-language course library
6. Social/competitive leaderboard features