Duolingo (/ˌdjˈlɪŋɡ/ DEW-oh-LING-goh) is an American edtech company which produces language-learning apps and provides language certification.

Duolingo, Inc.
Duolingo logo (2019).svg
Duolingo homepage.png
Duolingo homepage
Type of businessPublic company
Available inMultilingual
106 courses in 41 languages
Traded asNasdaqDUOL
HeadquartersPittsburgh, Pennsylvania, United States
Area servedWorldwide
Founder(s)Luis von Ahn, Severin Hacker
CEOLuis von Ahn
IndustryOnline education, Professional certification
ServicesLanguage courses, Duolingo English Test
RevenueIncrease US$251 million (2021)[1]
Operating incomeDecrease US$−60 million (2021)[1]
ProfitDecrease US$−60 million (2021)[1]
Total assetsIncrease US$661 million (2021)[1]
Total equityIncrease US$513 million (2021)[1]
Employees500+ (December 2021)[1]
Users49.2 million MAU[2]
Launched30 November 2011; 10 years ago (2011-11-30) (private beta)
19 June 2012; 10 years ago (2012-06-19) (public release)
Current statusOnline
Native client(s) onAndroid, iOS, Web Browser
Written inKotlin,[3] Swift,[4] React, Python, Scala,[5] HTML, CSS, JavaScript

On its main app users can practice vocabulary, grammar, and pronunciation using spaced repetition. Duolingo offers over 100 total courses across 41 distinct languages, from Spanish, French, German and Japanese to Navajo and Yiddish.[6] It also includes a small variety of constructed languages.[7] The company uses a freemium model with over 500 million registered users.[8] Duolingo offers a premium service which eliminates advertising and offers more features.

Duolingo also offers Duolingo English Test certification program and a literacy app for children: Duolingo ABC.


The idea for Duolingo was initiated at the end of 2009 in Pittsburgh by Carnegie Mellon University professor Luis von Ahn and his post-graduate student Severin Hacker.[9][10] Von Ahn had sold his second company, reCAPTCHA, to Google and, with Hacker, wanted to work on something related to education.[11] A driving motivation was Von Ahn's upbringing in Guatemala, where he saw how expensive it was for people in his community to learn English.[12] Swiss-born Hacker (co-founder and current CTO of Duolingo) believed that "free education will really change the world"[13] and wanted to supply people an outlet to do so.

The project was originally sponsored by Luis von Ahn's MacArthur fellowship and a National Science Foundation grant.[14][15] The founders considered creating Duolingo as a nonprofit organization but Von Ahn judged this model as unsustainable.[13] An early revenue stream was as a crowdsourced translation service. This was replaced as a source of revenue by a Duolingo English Test certification program, advertising and subscription.[16][17]

In October 2011, Duolingo announced that it had raised $3.3 million from a Series A round of funding, led by Union Square Ventures, with participation from author Tim Ferriss and actor Ashton Kutcher's investing firm A-Grade Investments.[18] Duolingo launched a private beta on 30 November 2011, and accumulated a waiting list of more than 300,000 people.[10][19] The platform launched to the general public on 19 June 2012, at which point the waiting list had grown to around 500,000.[20][21]

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.[22] In November 2012, Duolingo released a iPhone app,[23] followed an Android app in May 2013, at which time Duolingo had a user base of around 3 million.[24] By July 2013, the service had grown to 5 million users and was rated the #1 free education app in the Google Play store.[25]

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.[26] At this time, Duolingo had 34 employees and reported having about 25 million registered users and 12.5 million active users,[27] though it later reported a figure closer to 60 million users.[28]

In June 2015, Duolingo announced that it had raised $45 million from a Series D funding round led by Google Capital, bringing its total funding to $83.3 million. The round valued the company at around $470 million, with 100 million registered users globally.[16][28] In April 2016, it was reported that Duolingo had more than 18 million monthly users.[29][30]

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.[31] It was reported that Duolingo had 95 employees.[32] 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.[33] On 1 August 2018, Duolingo surpassed 300 million registered users.[34]

In December 2019, it was announced that Duolingo raised $30 million in a Series F funding round from Alphabet's investment company CapitalG.[35] The round valued Duolingo at $1.5 billion. Duolingo reported 30 million active users at this time. Headcount at the company had increased to 200, and new offices had been opened in Seattle, New York and Beijing.[36] 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.[37]

In March 2021, Duolingo announced that it will be ending its volunteer contributor program and donating money to its volunteer contributors who helped to make Duolingo. Language courses have been historically created by volunteers. The company said that from now on, language courses will be maintained and developed by professional linguists aligning with CEFR standards.[38] On 28 June 2021, Duolingo filed for an initial public offering on NASDAQ under the ticker DUOL.[39] In August 2021, the Duolingo language learning app was removed from some app stores in China.[40]


Duolingo appEdit

Duolingo language courses are built upon the concept of a "tree". Trees are composed of skills, which focus on a specific aspect of the target language. Trees are usually split into sections, or units, containing a chunk of related skills. Skills can be vocabulary and grammatically based, but other skills relating to color, idioms, relationships, and countries are also featured in courses. Skills are composed of six levels: levels 1, 2, 3, 4, 5, and Legendary. Users progress through levels on skills by practicing the lessons a certain number of times, usually 2 to 6, depending on the skill. Users also have the option to "test out" into the next level on a skill. Users also have the option to test out of entire units within a course. When users complete a lesson or test out, they are rewarded XP (experience points). Users are also tested on prior knowledge in future lessons as lessons will call back to previously learned words and expect the user to be able to apply them in new sentences.[41] Lessons can include matching, translating, speaking, and multiple choice.[42][43]Duolingo also provides a competitive space. In Leagues, people can compete against their friends or see how they stack up against the rest of the world in randomly selected groupings of up to 30 users. Rankings in leagues are determined by the amount of XP earned in a week. Badges in Duolingo represent achievements that are earned from completing specific objectives or challenges.[44]

In 2019, the company launched Duolingo Stories.[45] This feature consists of a small story for a particular situation to help improve learners reading and listening skills. Stories are available on the French, Spanish, German, Italian, Portuguese, and Japanese courses for English speakers, and some courses for users learning English (as these vary based upon the user's native language).[46]

For some languages Duolingo offers podcasts for people in intermediate level consisting on stories told usually by native speakers from different parts of the world where the target language is spoken, but with simplified grammar, vocabulary, and with a slower intonation, as well with occasional assistance with providing context or explanations of unusual words in the source language by a narrator.[47][48]

Duolingo provides "Duolingo for Schools", with features designed to allow teachers to track students' progress in language acquisition.

Languages offeredEdit

In October 2013, Duolingo launched a crowdsourced language incubator.[49] This produced courses in many languages, including constructed languages such as High Valyrian (A Song of Ice and Fire)[50] and Klingon (Star Trek).[51][52]

Language course Available in
Arabic English
Catalan Spanish
Haitian Creole English
Czech English
Danish English
Dutch English
English Arabic, Czech, Dutch, French, German, Greek, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Polish, Portuguese, Romanian, Russian, Spanish, Tagalog, Thai, Turkish, Ukrainian, Vietnamese
Esperanto English, French, Portuguese, Spanish
Finnish English
French Dutch, English, German, Italian, Japanese, Portuguese, Russian, Spanish
Scottish Gaelic English
German Arabic, Dutch, English, French, Hungarian, Italian, Portuguese, Russian, Spanish, Turkish
Greek English
Guarani Spanish
Hawaiian English
Hebrew English
Hindi English
Hungarian English
Indonesian English
Irish English
Italian English, French, German, Portuguese, Spanish
Japanese Chinese, English
Klingon English
Korean English, Japanese
Latin[53] English
Chinese English, Japanese, Vietnamese
Navajo English
Norwegian English
Polish English
Portuguese English, French, Spanish
Romanian English
Russian English, Spanish, Turkish
Spanish English, French, German, Italian, Portuguese, Russian
Swahili English
Swedish Arabic, English, Spanish
Turkish English
Ukrainian English
High Valyrian English
Vietnamese English
Welsh English
Yiddish English

Duolingo ABCEdit

Duolingo ABC is a mobile app for young children for learning letters, their sounds, phonics, and other foundational early reading concepts that was released in 2020.[54] [55]

Duolingo English TestEdit

Duolingo English Test (DET) is a standardized test of English language proficiency for non-native English language speakers.

Business modelEdit

Most language-learning features in Duolingo are free of charge, but it has periodic advertising in both its mobile and web browser applications, which users can remove by paying a subscription fee or invite links.[56][57] This feature is known as "Super Duolingo" (formerly Duolingo Plus)[58] and includes benefits such as unlimited hearts (retries), level skipping, no ads, and progress quizzes.

Duolingo had a revenue of $1 million in 2016, $13 million in 2017,[34] $36 million in 2018,[59] and $250.77 million in 2021.[60] In May 2022, it was reported that 6.8% of Duolingo's monthly active users pay for the ad-free version of the app. Duolingo derived most of its revenue from subscription, advertising, and its Duolingo English Test.[61] In April 2020, Duolingo passed one million paid subscribers.[62] In March 2022, it had 2.9 million paid subscribers.[63]

In 2021, Duolingo became a publicly-traded company using the Nasdaq symbol DUOL.[64][65]


Duolingo utilizes the Amazon Web Services (AWS) product suite, including Amazon DynamoDB, Amazon Virtual Private Cloud, nearly 200 virtual instances in Amazon Elastic Compute Cloud (EC2), Amazon Simple Storage Service (S3) and Amazon Relational Database Service (RDS).[66] The website's backend is written in the programming language Python.[better source needed] A component called the Session Generator was rewritten in Scala by 2017.[5] The front end was written in Backbone.js and Mustache but is now primarily in React and Redux.[66] Duolingo uses Amazon Polly for voice synthesis.[67]

Duolingo provides a single-page web application for desktop computer users and also smartphone applications on Android (both Google Play Store and Amazon Appstore) and iOS App Store platforms. 20% of traffic comes from desktop users and 80% from mobile app users.[66]



Duolingo has received criticism for its lack of effectiveness in helping students to develop fluency or real proficiency in a language. The company's CEO promises only to get users to a level between advanced beginner and early intermediate, saying "A significant portion of our users use it because it's fun and it's not a complete waste of time."[68]

After six months of studying French with Duolingo, von Ahn demonstrated a lack of basic verb tenses when asked to describe his weekend in French, "mangling his tenses." Bob Meese, Duolingo's chief revenue officer, did not immediately understand the spoken question "¿Hablas español?" ("Do you speak Spanish?" in Spanish) after six months of Duolingo Spanish language study.[69]

Linguist Steven Sacco at San Diego State University attempted to test Duolingo's claim that "34 hours of Duolingo are equivalent to a full university semester of language education"[70] by completing a course in Swedish, and taking a standardized elementary exam, ultimately receiving a failing grade.[71] Sacco suggested that Duolingo is helpful for learning vocabulary only in addition to immersion environments like a classroom.[71]

In 2012, an effectiveness study concluded that Duolingo usage for Spanish study was more effective than classroom language-learning alone, but that Duolingo was less effective for advanced language-learners.[72] One proposed reason for this is that the grammar-translation method that Duolingo primarily uses is more applicable to simple words and phrases than to complex ones; simpler ones can translate in a more exact manner from one language to another and thus are more conducive to Duolingo's method.[73]


In 2013, Apple chose Duolingo as its iPhone App of the Year, the first time this honor had been awarded to an educational application.[74] In 2013, Duolingo ranked #7 on Fast Company's "The World's Most Innovative Companies: Education Honorees" list "for crowdsourcing web translation by turning it into a free language-learning program".[75][76][77] Duolingo won Best Education Startup at the 2014 Crunchies,[78][better source needed] and was the most downloaded app in the Education category in Google Play in 2013 and 2014.[79]

In 2015, Duolingo was announced the 2015 award winner in Play & Learning category by Design to Improve Life.[80][better source needed] Duolingo won Inc. magazine's Best Workplaces 2018,[81] Entrepreneur magazine's Top Company Culture List 2018,[82] and appeared in CNBC's 2018 and 2019 "Disruptor 50" lists[83][84][85] and TIME magazine's 50 Genius Companies.[86] In 2019, Duolingo was named one of Forbes's "Next Billion-Dollar Startups 2019".[87] In July 2020, Duolingo was named by PCMag as "The Best Free Language Learning App."[88]

In popular cultureEdit

Duolingo's mascot, a green cartoon owl named Duo, has been a subject of an Internet meme in which the mascot is "evil" and will stalk and threaten users if they do not keep using the app such as breaking a streak.[89] Acknowledging the meme, Duolingo released a video on 1 April 2019; the video depicts a new feature called "Duolingo Push". In the video, users of "Duolingo Push" will receive reminders to use the app in person by Duo himself, who stares at users and follows them around until they use the app (in the video, Duo is depicted by a person in a large mascot costume).[90][91] On 1 April 2022, Duolingo released another video in the form of a spoof legal advertisement where the lawyers sue the company for damages due to family members going missing, once again alluding to the meme.[92]

In November 2019, Saturday Night Live parodied Duolingo in a sketch in which adults learn to communicate with children using a fictitious course on the app entitled "Duolingo for Talking to Children".[93]

See alsoEdit


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External linksEdit