Data AnalysisConsumer FacingVerified
Reviewed and published by trentmaziarz, March 21, 2026. Discovered and drafted by our automated research pipeline.
The Duolingo English Test is the first major standardized language proficiency exam where AI handles every stage of the process — writing the test questions, calibrating their difficulty, choosing which questions each test-taker sees, grading answers, and producing final scores. The test costs $65, takes about an hour, and is accepted by more than 5,000 universities worldwide.
Details
Described in a peer-reviewed 2020 paper published in MIT Press's Transactions of the Association for Computational Linguistics, the Duolingo English Test uses machine learning and natural language processing (NLP) models to automatically generate thousands of test items and align them to CEFR proficiency levels. A computer-adaptive testing approach means each test-taker sees a customized set of questions selected in real time based on their performance, so no two tests are identical. Scores on the 10–160 scale correlate with TOEFL and IELTS at .73 — comparable to the correlation those two tests have with each other. A test-taker would encounter a repeated item only after approximately 1,000 sessions, demonstrating the system's breadth.
Products affected
Duolingo English Test
Sources & Evidence
Other practices by Duolingo
Customer SvcDuolingo uses an AI chatbot (powered by a company called Decagon) to handle the majority of customer support requests for the Duolingo English Test. The AI fully resolves about 80% of chat inquiries without any human involvement, answering questions about test registration, scores, and institutional acceptance.Data AnalysisDuolingo uses a machine learning model to decide, in real time, whether to show each individual user an advertisement, a subscription offer, or neither — predicting which choice is most likely to generate revenue from that specific person at that moment. The system was credited with generating tens of millions of dollars in additional annual revenue.Data AnalysisDuolingo uses a machine learning algorithm to decide which push notification to send each user, at what time, and how often — optimizing for the messages most likely to get a lapsed learner back into the app. The system was published as research in 2020 and was shown to increase the number of daily active users by 0.5% and improve retention of new users by 2%.
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