Duolingo

Early history 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. Von Ahn had sold his second company, reCAPTCHA, to Google and, with Hacker, wanted to work on an education-related project. Von Ahn stated that he saw how expensive it was for people in his community in Guatemala to learn English. The Duo mascot is a green owl because co-founder Severin Hacker hates the color green. The project was originally financed by von Ahn's MacArthur fellowship and a National Science Foundation grant. The founders considered creating Duolingo as a nonprofit organization, but von Ahn judged this model unsustainable. Duolingo launched a private beta on November 30, 2011, and accumulated a waiting list of more than 100,000 people by December 13. It launched to the general public on June 19, 2012, at which point the waiting list had grown to around 500,000. 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. In November 2012, Duolingo released an iPhone app, followed by an Android app in May 2013, at which time Duolingo had around 3 million users. By July 2013, it had grown to 5 million users and was rated the No. 1 free education app in the Google Play Store. 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. At this time, it had 34 employees, and reported about 25 million registered users and 12.5 million active users; In April 2016, it was reported that Duolingo had more than 18 million monthly users. In July 2017, Duolingo announced that it had raised $25 million in a Series E funding round led by Drive Capital, bringing its total funding to $108.3 million. The round valued Duolingo at $700 million, and the company reported passing 200 million registered users, with 25 million active users. It was reported that Duolingo had 95 employees. Funds from the Series E round would be directed toward creating initiatives such as a related educational flashcard app, TinyCards, and testbeds for initiatives related to reading and listening comprehension. On August 1, 2018, Duolingo surpassed 300 million registered users. In December 2019, it was announced that Duolingo raised $30 million in a Series F funding round from Alphabet's investment company, CapitalG. The round valued Duolingo at $1.5 billion. Duolingo reported 30 million active users at this time. The headcount at the company had increased to around two hundred, and new offices had been opened in Seattle, New York, and Beijing. Duolingo planned to use the funds to develop new products and further expand its team in sectors like engineering, business development, design, curriculum and content creators, community outreach, and marketing. Features and media In October 2013, Duolingo launched a crowdsourced language incubator. Initially relying on volunteers developing its courses, in March 2021 Duolingo announced that it would be ending its volunteer contributor program. The company said that language courses would instead be maintained and developed by professional linguists aligning with CEFR standards. On June 28, 2021, Duolingo filed for an initial public offering on NASDAQ under the ticker DUOL. From August 2021 to June 2022, the Duolingo language learning app was removed from some app stores in China. In March 2022, Duolingo discontinued its community forums. 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. This update has been criticized by users across social media outlets, such as Reddit and X (formerly Twitter). CEO Luis von Ahn stated that there were no plans to reverse the changes. In October 2022, Duolingo acquired Detroit-based animation studio Gunner, a long-time design and animation partner that had produced graphics and animations for Duolingo, Duolingo ABC, and the company’s marketing campaigns. In March 2023, Duolingo officially announced the planned Duolingo Max, a subscription tier above Super Duolingo, in their blog. In October 2023, Duolingo released math and music courses in English and Spanish for iOS users. In January 2024, Duolingo fired around ten percent of its contract workforce and announced plans to replace them with AI. The company acquired Detroit-based design studio Hobbes in March. Duolingo announced plans to expand its music education offerings after acquiring London-based NextBeat, a music and gaming start-up company. == Products and services ==

Courses Language courses CEFR based language courses for learners of English, Spanish, French, Italian, Chinese (Mandarin), Japanese, Korean, Portuguese, and German are available for all users. Additional courses are also available for speakers of English (Arabic, Czech, Danish, Dutch, Esperanto, Finnish, Greek, Haitian Creole, Hawaiian, Hebrew, High Valyrian, Hindi, Hungarian, Indonesian, Irish, Klingon, Latin, Navajo, Norwegian, Polish, Romanian, Russian, Scottish Gaelic, Swahili, Swedish, Turkish, Ukrainian, Vietnamese, Welsh, Yiddish, Zulu), Chinese (Chinese (Cantonese)), Arabic (Swedish), and Spanish (Catalan, Guarani, Russian, Swedish). Subscriptions Super Duolingo As of 2014, most of Duolingo's language learning features are free with advertising. Users can remove advertising by paying a subscription fee or promoting referral links. The paid user program, Super Duolingo (formerly known as Duolingo Plus), offers unlimited retries and access to some additional types of lessons. It is otherwise identical to Duolingo for Schools. Duolingo Max Duolingo Max is a subscription above Super Duolingo that adds additional functions using generative AI: Roleplay, an AI conversation partner; and Video Call, where users can video chat with one of the characters, which currently includes only Lily. It is intended to provide immersion through conversation. Explain My Answer - a AI generated feature to help users understand their mistakes - used to be Max exclusive, but is now free for all users as of 2026. Duolingo for Schools Duolingo for Schools is designed to help teachers use Duolingo in their classrooms. It allows teachers to create classrooms, assign lessons, track student progress, and personalize learning. Duolingo English Test The Duolingo English Test (DET) is an online English proficiency test that measures proficiency in reading, writing, speaking, and listening in English. It is a computer-based test scored on a scale of 10–160, with scores above 120 considered English proficiency. The test's questions algorithmically adjust to the test-takers' ability level. Other programs Duolingo Math was an app course for learning elementary mathematics. It was announced on YouTube on August 27, 2022. It was merged into Duolingo in 2024, now available as a course. On October 11, 2023, the company released Duolingo Music, Duolingo introduced chess lessons in beta on April 22, 2025, with an initial rollout planned for iOS in English by May. The lessons are structured around the Elo rating system, gradually increasing in difficulty to match the user's skill level. Learners can play mini-matches or full games against Duolingo's virtual chess coach, Oscar, whose difficulty also scales with progress. At launch, users are not able to play against each other. is a free app designed for young children to learn letters, their sounds, phonics, and other early reading concepts. Released in 2020, it does not contain ads or in-app purchases. As of April 2024, iOS and Android versions are available, but only in English. == Learning model ==

Exercises and pacing On Duolingo, learners learn by doing, engaging with the course material. Lessons are designed to be brief, allowing users to learn in manageable chunks. Duolingo uses a gamified approach to learning, with lessons that incorporate translating, interactive exercises, quizzes, and stories. It also uses an algorithm that adapts to each learner and can provide personalized feedback and recommendations. Gamification Duolingo provides a competitive space, such as in leagues, where people can compete with randomly selected groupings of up to 30 users. Leagues: Bronze, Silver, Gold, Sapphire, Ruby, Emerald, Amethyst, Pearl, Obsidian, Diamond. Rankings in leagues are determined by the number of experience points earned in a week. Badges in Duolingo represent achievements earned from completing specific objectives. Users can also create their own avatars. Any lesson completed in Duolingo will count towards the user's daily streak. Streaks encourage consistent daily practice and help build a habit of regular learning. The app has a personalized bandit algorithm system (later the A/B tested variant recovering difference softmax algorithm) that determines the daily notification that will be sent out to the user. Duolingo Score The Duolingo Score is an estimate of users' proficiency in the language they're learning in CEFR-aligned courses. Duolingo Score provides a granular assessment of what a student has learned and what they can do with the language. DET is using a similar scoring system. The most developed CEFR-aligned courses (French, English and Spanish) cover Duolingo Score from 0 to 130. == Business model ==

Duolingo operates on a freemium business model, offering free access to its learning platforms with ads. Revenue is primarily generated through subscriptions, which remove ads, and provide other perks like unlimited energy (formerly hearts) and generative AI. The app also generates income from in-app purchases of virtual currency (Gems) and power-ups that enhance the learning experience. Another key revenue stream is the Duolingo English Test (DET), a low-cost English proficiency test. In April 2020, it passed one million paid subscribers; it reached 2.9 million in March 2022, and 4.8 million at the end of March 2023. As of June 2025, Duolingo has 10.9 million paying subscribers. Duolingo had revenue of $531 million in 2023, compared to $250.77 million in 2021, $36 million in 2018, $13 million in 2017, Generative AI usage Starting from 2024, Duolingo began to cut some of their staff following steps to incorporate AI into its platform. By 2025, Duolingo planned to introduce 150 courses created using generative AI. Most of the courses created using AI were aimed at non-English speakers, such as the introduction of courses in several East Asian languages such as Japanese and Korean for Spanish speakers. This move caused controversy with language researchers stating that the use of AI-generated content could take work away from future translators, as the courses would lose nuance in social-cultural aspects of certain languages that AI models cannot understand. In addition, company executives were questioned about statements indicating that the use of AI is much more effective than human teaching. These comments were removed from much of Duolingo's social media following backlash from users as well as professional translators. In 2025, CEO Luis von Ahn announced Duolingo would become an "AI-first" company and would be replacing contracted workers with artificial intelligence through automation. This decision was met with public outcry, leading many users to unsubscribe and end their learning streaks in protest. Many criticized the Duolingo app for losing its quality due to this change. In May 2025, due to backlash against the perceived threat of workers being replaced by inferior-quality AI, Duolingo's Instagram and TikTok videos were flooded with comments expressing anger at the company. Duolingo took down all videos from both channels. Duolingo's social media accounts had previously been described as models of success in marketing. The company later uploaded a video which sarcastically attempted to downplay the controversy, followed by a video from the CEO attempting to clarify the company's use of generative AI technology. When asked about the backlash during Duolingo's August 2025 earnings call, CEO Luis von Ahn said: "We just don't believe that the effect of this is very material in terms of when you're looking at actual financial metrics." == Reception ==

Effectiveness A 2017 study found no significant difference between elementary students learning Spanish through the "gamification" of the Duolingo app and those learning in classroom environments, with both groups demonstrating a similar increase in achievements and self-efficacy. 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"—is reportedly derived from research published in 2018 by psychologists at Ghent University in Belgium, 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. 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. According to Duolingo's own 2021 study, five sections of the app are roughly equivalent to five semesters of university instruction, and Duolingo is an "effective tool [...] at an intermediate level". A 2023 study funded by Duolingo concluded that Duolingo English learners did not significantly learn much grammar. Duolingo English learners in Colombia and Spain were found to gain significantly more proficiency than students in a classroom, except for listening. Criticism Some language professionals have criticized the app for its limitations and gamified design. Users 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. Duolingo later stated that they would investigate the "dark web post". They concluded that the data was obtained by scraping publicly available information based on an exposed application programming interface (API). Duolingo's spokesperson states that the API is intentionally publicly visible. Since the end of October 2023, Duolingo has stopped updating its Welsh course to "focus on languages in higher demand". Some users criticized this decision because it came at the expense of learners of a language with limited resources on the market and the potential halting of the Welsh Government "Cymraeg 2050" strategy to promote Welsh language learning. Bruno Estigarribia stated that, as of 2019, the Guarani course was "seemingly in a development phase" and that it "had many inconsistencies". He added this course could serve as a complement to one's studies, but it would not "magically teach" the language. In January 2024, Duolingo fired about 10% of contractors, stating that "Generative AI is accelerating our work by helping us create new content dramatically faster." In April 2025, Duolingo announced they would gradually stop using contractors where "AI" can do the work, urging employees to "take occasional small hits on quality [rather] than move slowly and miss the moment" in order to become an "AI-first" company. This statement was received poorly, and a follow-up post, where the CEO claims he was misunderstood, led to further critique. Awards In 2013, Apple named Duolingo as its "iPhone App of the Year". Duolingo won "Best Education Startup" at the 2014 Crunchies, and was the most downloaded education app in Google Play in 2013 and 2014. In 2015, the Duolingo company won the Index Award in the Play & Learning category. == Image and brand ==

Duolingo's characters Duolingo has brand characters that are used for engagement and creating storylines. The main characters include Duo Keyshauna Renee Lingo, commonly known as Duo or Duo the Owl, the company's green owl mascot. On February 11, 2025, Duolingo announced, as part of a publicity stunt, that Duo had died, after being hit by a Tesla Cybertruck. Later, Duolingo put up a website where the users of the app would have to work together to obtain 50 Billion in-app experience to resurrect Duo. After the goal was reached, Duolingo then posted a video on their social medias of Duo's resurrection. The company also stated the character's birth date as 1000BC, and his full name as Duo Keyshauna Renee Lingo. Duo served as the motivational face of the app, encouraging users to complete their lessons and maintain their learning streaks. Duo has become a well-known internet character, often depicted humorously as aggressively reminding users to not miss their streaks. Over time, Duo has gained a significant reputation in memes for being persistent—even threatening—about keeping users on track with their lessons. According to Duolingo Brand Guidelines, "Duo is a boy" and communicates through text only. In popular culture Due to the app's frequent reminder notifications, Duolingo's mascot, a green cartoon owl named Duo, has been the subject of Internet memes antagonizing him, with the character often depicted stalking or threatening users if they do not continue using the app. Duolingo has leaned into its online reputation and has adjusted its social media and marketing strategies accordingly. Acknowledging the meme, Duolingo released a video on April Fools' Day 2019, depicting a facetious new feature called "Duolingo Push". In the video, users of "Duolingo Push" are reminded to use the app by Duo himself (depicted by a person wearing a Duolingo mascot costume), who stares at and follows them until they comply. It was also acknowledged during Duolingo's 2022 April Fools' Day video, "Lawyer Fights Duolingo Owl for $2,700,000", where a fictitious law firm fights for those that have been harmed by Duolingo's owl mascot. 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." In November 2019, Saturday Night Live parodied Duolingo in a sketch where adults learned to communicate with children by using a fictitious course called "Duolingo for Talking to Children". ==Offices and workforce==

Duolingo is headquartered in Pittsburgh, Pennsylvania. Duo's Taqueria is an adjacent taco stand operated by Duolingo. The restaurant encourages patrons to order in Spanish. Duolingo's taco shop brought in $700,000 in 2023. In 2024, Duolingo opened a new office in New York City. Duolingo also has offices in Seattle, Detroit, As of October 2024, Duolingo employs around 850 people. == See also ==