Duolingo
Free tierLearn a language for free — powered by AI and gamification
Free tier available·All audiences·Powered by OpenAI (GPT-4)
Key strengths
Gamified learning with streaks, XP, and leaderboardsAI-powered personalized lesson paths40+ languages supportedBite-sized lessons optimized for habit formationGPT-4-powered Roleplay and Explain My Answer features (Max tier)
Free tier + paid plans · from $6.99 USD/mo
Pittsburgh, USA
Founded 2011
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Technical Integration & Developer Notes
Duolingo does not offer a public REST API for third-party developers at this time. All learning features are delivered through its own iOS, Android, and web clients.
AI Features (Duolingo Max — GPT-4 Powered)
- Roleplay: Users engage in open-ended conversations with AI characters in real-world scenarios (e.g., ordering food, checking into a hotel). Responses are generated dynamically via GPT-4.
- Explain My Answer: After completing an exercise, users can tap to receive a natural-language explanation of why their answer was correct or incorrect, powered by GPT-4.
Adaptive Learning Engine
- Uses spaced repetition and item response theory (IRT) models to calibrate exercise difficulty per user.
- Duolingo's internal ML team publishes research on its learning models; key papers are available via the Duolingo Research blog.
Platforms Supported
- iOS (iPhone & iPad), Android, Web (Chrome, Firefox, Safari, Edge)
- Offline lesson downloads available on mobile
Data & Privacy
- Complies with COPPA (for users under 13 via Duolingo for Schools), GDPR, and CCPA.
- Duolingo for Schools provides a teacher dashboard with student progress tracking — accessible at schools.duolingo.com.