Duolingo

Free tier

Learn a language for free — AI-powered lessons that adapt to you

Free tier available·All audiences·Powered by OpenAI (GPT-4 for Duolingo Max features)

Key strengths

Adaptive AI-powered lesson personalizationGamified learning with streaks, XP, and leaderboards40+ languages supportedAI conversation practice (Duolingo Max)Bite-sized lessons optimized for habit formation

Free tier + paid plans · from $6.99 USD/mo

Pittsburgh, USA

Founded 2011

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EdTech research reference — Duolingo publishes academic papers on its ML-based knowledge modeling and spaced repetition systems, serving as a benchmark for adaptive learning research.
A/B testing at scale — Duolingo's infrastructure handles continuous multivariate experiments across hundreds of millions of users, a model studied by growth and product engineering teams.
LLM integration case study — the Duolingo Max rollout (GPT-4 for Roleplay and Explain My Answer) is a widely cited production example of integrating large language models into a consumer education product.
Mobile-first ML deployment — Duolingo's on-device and server-side ML pipelines for personalization serve as a reference architecture for mobile AI product teams.
Gamification and engagement mechanics — product engineers and designers study Duolingo's streak, XP, and leaderboard systems as canonical examples of behavioral loop design in apps.

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