Duolingo, Inc.[b] is an American educational technology company that produces learning apps and provides language certification.

[8] The learning method incorporates gamification to motivate users with points, rewards and interactive lessons featuring spaced repetition.

[16][17] The idea of Duolingo was formulated in 2009 by Carnegie Mellon University professor Luis von Ahn and his Swiss-born post-graduate student Severin Hacker.

[18][19] Von Ahn had sold his second company, reCAPTCHA, to Google and, with Hacker, wanted to work on an education-related project.

[21][22] Hacker (co-founder and current CTO of Duolingo) believed that "free education will really change the world"[23] and wanted to provide an accessible means for doing so.

[25] The project was originally financed by von Ahn's MacArthur fellowship and a National Science Foundation grant.

[23] Its early revenue stream, a crowdsourced translation service, was replaced by a Duolingo English Test certification program, advertising, and subscription.

[34][35] In September 2012, Duolingo announced that it had raised a further $15 million from a Series B funding round led by New Enterprise Associates, with participation from Union Square Ventures.

[39] In February 2014, Duolingo announced that it had raised $20 million from a Series C funding round led by Kleiner Caufield & Byers, with prior investors also participating.

[47] In December 2019, it was announced that Duolingo raised $30 million in a Series F funding round from Alphabet's investment company, CapitalG.

[54][55] In August 2022, Duolingo overhauled its interface, changing its course structure from a tree-like design, where users could choose from a range of lessons after completing previous ones, to a linear progression.

[58][59] In 2024, Duolingo made several changes: it replaced some contractor tasks with AI in January,[60] launched the widget feature on Android in March,[61] acquired Detroit-based design studio Hobbes, introduced Friend Streak in August, allowing students to share a streak together with their friends,[62] and released math and music courses for Android in September.

[66] In the fall of 2024, Duolingo started releasing or beta testing new CERF based language courses for learners of English (B2), Spanish (A2), French (A2), Italian (A1), Chinese (A1), Japanese (A1), Korean (A1), and German (A1) for all of its users.

[77] Most of Duolingo's language learning features are free, with advertising in its mobile and web browser applications, which users can remove by paying a subscription fee or promoting referral links.

[79][80] Duolingo Max is a subscription above Super Duolingo that adds additional functions using generative AI: Roleplay, an AI conversation partner; Explain My Answer, which breaks down the rules with a modified GPT-4 when the user makes a mistake; and Video Call, where users can have video chat with one of the characters, which currently only includes Lily.

[83] Duolingo ABC is a free app designed for young children to learn letters, their sounds, phonics, and other early reading concepts.

Duolingo provides a competitive space,[93] such as in leagues, where people can compete with randomly selected worldwide player groupings of up to 30 users.

On the Duolingo Blog, they wrote that they "decided to come up with a series of illustrations that would show Duo’s mood at different parts of the day".

The app also generates income from in-app purchases of virtual currency (Gems) and power-ups that enhance the learning experience.

[108] Duolingo's occasional use of 'erratic' phrases—such as "The bride is a woman and the groom is a hedgehog" or "The man eats ice cream with mustard"[109]—is reportedly derived from research published in 2018 by psychologists at Ghent University in Belgium,[110] which concluded that such "semantically unpredictable sentences" were more effective for language learning than conventional and predictable phrases, based on the concept of "reward prediction errors", in which unexpected or surprising outcomes are more rewarding and thus encourage further learning.

[112] Another 2022 study of Malaysian students learning French, published by the National University of Malaysia Press, found that the app facilitated the acquisition of vocabulary and concluded that it was "well suited" for beginners in this regard.

[116] Duolingo English learners in Colombia and Spain were found to gain significantly more proficiency than students in a classroom, except for listening.

[118] Players have also reported that "gamification" has led to cheating, hacking, and incentivized game strategies that conflict with actual learning.

In January 2023, Duolingo's data on over 2.6 million users' usernames, names, and phone numbers was sold in a hacker forum.

[122] They concluded that the data was obtained by scraping publicly available information based on an exposed application programming interface (API).

[165] This was further referenced by the company in its 2024 April Fools' Day skit "Duo on Ice", in which the owl, in a mix of Spanish and English, admitted to having an appetite for human flesh, and if the user failed to continue their streak, they would "eat their head like a praying mantis.

[167] Duolingo has effectively engaged with Generation Alpha through its YouTube shorts, featuring global meme trends and content like songs, workplace insights, and humor, including elements of dark comedy, and "kidnapping children" as a joke.

The conference serves as a platform to share the latest updates, features, and future plans of the app, while also exploring broader topics related to language learning and technology.

[171] The restaurant encourages patrons to order in Spanish, aligning with Duolingo's mission of making language learning fun and accessible.

[175] In 2024, Duolingo opened a new office in New York City, featuring an art gallery in which the company's characters are depicted in the style of famous historical paintings.