Duolingo is a language learning app with Spaced repetition memory system components.

It drew $100M in revenue in 2019 from advertising and subscriptions. At that time, it claimed around 30M monthly active users; its subscription costs $7/mo. So that would represent about 1.1M annual subscriptions if one assumes 0% revenue from advertising.

Jiang et al find that Duolingo compares favorable with fourth semester university courses (roughly equal outcomes in fewer hours).


Jiang, X., Rollinson, J., Plonsky, L., & Pajak, B. (2020). Duolingo efficacy study: Beginning-level courses equivalent to four university semesters. 11.

Last updated 2023-07-13.