Duolingo uses generative AI to write lesson exercises, dialogues, and entire language courses. Human experts set the rules — the target language, skill level, and grammar topic — and the AI produces the content for human review. In April 2025, Duolingo launched 148 new courses built primarily this way, roughly doubling its total course offerings in about one year.

Disclosed in a June 2023 blog post, Duolingo's system has Learning Designers write a structured prompt — specifying language, Common European Framework of Reference (CEFR) proficiency level, grammar focus, and lesson theme — and a generative AI model then produces batches of exercises that humans review and edit before publication. CEO Luis von Ahn stated in 2025 that content creation is now "close to 100%" AI-generated. The April 2025 course launch was significant: the first 100 Duolingo courses took 12 years to build manually, while 148 new courses were created in approximately one year using AI. In February 2026, Duolingo also replaced its flagship Spanish and French courses with new AI-generated versions.