Duolingo (/ˌdˈlɪŋɡ, dj-, dʒ-/ D(Y)OO-oh-LING-goh) is an American language-learning website and mobile app, as well as a digital language proficiency assessment exam. The company uses the freemium model; the app and the website are accessible without charge, although Duolingo also offers a premium service for a fee.

Duolingo, Inc.
Duolingo logo (2019).svg
Duolingo homepage.png
Duolingo homepage
Type of businessPrivately held company
Available in
HeadquartersPittsburgh, Pennsylvania, United States
Area servedWorld
Founder(s)Luis von Ahn, Severin Hacker
CEOLuis von Ahn
IndustryOnline education, Professional certification, Translation, Crowdsourcing
ServicesLanguage courses, Duolingo English Test, Duolingo for Schools, Tinycards flashcard app
RevenueIncrease$ 36 million USD in 2018[1]
Users>300 million users[3]
Launched30 November 2011; 9 years ago (2011-11-30) (private beta)
19 June 2012; 8 years ago (2012-06-19) (public release)
Current statusOnline
Native client(s) onAndroid, iOS, Windows Phone, Windows 10 Mobile, Web Browser
Written inKotlin,[4] Swift,[5] React, Python, Scala[6]HTML, CSS, JavaScript

As of 10 February 2021, the language-learning website and app offered 106 different language courses in 38 languages.[7] The app has over 300 million registered users across the world.[8][9][10][11]


The project[clarification needed] was initiated at the end of 2009 in Pittsburgh by Carnegie Mellon University professor Luis von Ahn (creator of reCAPTCHA) and his graduate student Severin Hacker.[12][13][14]

The inspiration for Duolingo came from two places. Luis von Ahn wanted to create a program that served two purposes in one program.[15] Duolingo originally achieved this by teaching its users a foreign language while having them translate simple phrases in documents, though the translation feature has since been removed.[16]

Von Ahn was born in Guatemala. He saw how expensive it was for people in his community to learn English. Severin Hacker (born in Zug, Switzerland), co-founder of Duolingo and current CTO, and von Ahn believed that "free education will really change the world"[17] 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.[18][19]

On October 19, 2011, Duolingo raised $3.3 million from a Series A first-round of funding, led by Union Square Ventures, with participation from author Tim Ferriss and actor Ashton Kutcher's firm, A-Grade Investments [20][21][22]

Duolingo launched into private beta a month later on November 30, 2011, and accumulated a waiting list of more than 300,000 users.[23][24][14]

On June 19, 2012, Duolingo later launched for the general public.[25]

On September 17, 2012, Duolingo raised $15 million from a Series B second-round of funding led by New Enterprise Associates, with participation from Union Square Ventures bringing Duolingo's total funding to $18.3 million.[26]

On 13 November 2012, Duolingo released their iOS app through the iTunes App Store.[27] The application is a free download and is compatible with most iPhone, iPod and iPad devices.[28]

On 29 May 2013, Duolingo released their Android app, which was downloaded about a million times in the first three weeks and quickly became the #1 education app in the Google Play store.[29]

On June 19, 2013, one year after launching for the general public, Duolingo passed 4 million users, all through word of mouth,[30] and on November 21, 2013, Duolingo reached 15 million users.[30]

On February 18, 2014, Duolingo raised $20 million from a Series C round of funding led by Kleiner Caufield & Byers.[31] It was reported Duolingo had had about 25 million registered users, 12.5 million active users, and 34 employees.[32] On June 2, 2014, Duolingo passed 30 million users.[30]

On June 10, 2015, Duolingo raised $45 million from a Series D fourth-round of funding led by Google Capital, bringing its total funding to $83.3 million, a valuation of $470 million, as well as passing 100 million users.[33][34][35]

In April 2016, it was reported that Duolingo had 17 million monthly users.[36][37]

On July 25, 2017, that Duolingo raised $25 million from a Series E fifth-round of investment from Drive Capital, bringing its total funding to $108.3 million, a valuation of $700 million, as well as passing 200 million users and having 25 million monthly users.[38][39] It was reported that Duolingo had 95 employees,[40] and the funds would be directed toward creating initiatives such as TinyCards and Duolingo Labs.[41]

On August 1, 2018, it was reported Duolingo had passed 300 million users.[42]

On December 4, 2019, it was announced that Duolingo raised $30 million in a series F sixth-round of investment from Alphabet’s investment company CapitalG, bringing a total funding of $138.3 million, a valuation of $1.5 billion, reporting 30 million monthly active learners.[43] Duolingo will use the funds on developing new products and expanding its team. Expanding the team will span a variety of positions, including in engineering, business development, design, curriculum and content creators, community outreach and marketing.[44]

During 2019, Duolingo grew from 170 staff members[45] to 200 employees,[40] with headquarters in the Pittsburgh neighborhood of East Liberty[46][47][48] and offices in New York; Bellevue, Washington (near Seattle); and Beijing.[40][49] Of Duolingo’s 199 employees, 165 work in its East Liberty headquarters, 17 work in New York, 8 in Bellevue, and 8 in China.[44]

Duolingo had a revenue of $1 million in 2016, $13 million in 2017,[42] $36 million in 2018,[45] and was projected to hit $86 million in 2019.[50] In April 2020, Duolingo passed one million paid subscribers.[51]


Duolingo mimics the structure of video games in several ways to engage its users. It features a reward system in which users acquire "lingots" or gems, an in-game currency that they can spend on features such as character customizations or bonus levels (both available on the mobile app only).

On public leaderboards, 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. The level system that Duolingo uses is XP (experience points), a numerical system that represents a user's skill level. Badges in Duolingo represent achievements that are earned from completing specific objectives or challenges.[52]

The study process in Duolingo combines various methods such as: listening to the pronunciation, reading sentences, voice recording, forming phrases by ordering words, and matching images to words.[53]

Use in schoolsEdit

Duolingo provides "Duolingo for Schools" with features designed to allow teachers to track students' progress. 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.[54] 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 grammar-translation method.[55]


Duolingo Incubator[56] is a platform where volunteers can participate and contribute to creating new language courses for Duolingo. A volunteer willing to participate must be a registered Duolingo user and has to go through the application process before contributing to a particular course they are interested in. This initiative allowed Duolingo to create more courses hence increasing their community to reach the maximum potential of the language learners.

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,[57][58] which users can remove by paying a subscription fee. This feature, ‘Duolingo Plus’, includes benefits such as unlimited hearts, level skipping, and progress quizzes. It originally employed a crowd sourced business model, where the content came from organizations (such as CNN and BuzzFeed) that paid Duolingo to translate it.[59]


Duolingo utilizes many services in the Amazon Web Services suite of products, 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).[60] The server backend is written in the programming language Python.[better source needed] A component called the Session Generator was rewritten in Scala by 2017.[6] The frontend was written in Backbone.js and Mustache but is now primarily in React and Redux. Duolingo provides a single-page web application for desktop computer users and also smart phone 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.[60]

Recognition and awardsEdit

In 2013, Apple chose Duolingo as its iPhone App of the Year, the first time this honor had been awarded to an educational application.[61] Duolingo won Best Education Startup at the 2014 Crunchies,[46] and was the most downloaded app in the Education category in Google Play in 2013 and 2014.[62] In 2015, Duolingo was announced the 2015 award winner in Play & Learning category by Design to Improve Life.[63]

Duolingo was named No. 44 on Fast Company's "The World's 50 Most Innovative Companies" list in 2018 "for making new languages irresistible".[64] No. 2 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2018 "for making a new language irresistible",[65] and No. 2 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2017 "for letting friends compare notes as they learn a new language".[66] No. 6 on Fast Company's "The World's Most Innovative Companies: Social Media Honorees" in 2017 "for letting friends compare notes".[67] No. 7 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2013 "for crowdsourcing web translation by turning it into a free language-learning program".[68]

Duolingo won Inc. magazine's Best Workplaces 2018,[69] Entrepreneur magazine's Top Company Culture List 2018,[70] and appeared in CNBC's 2018 and 2019 "Disruptor 50" lists.[71][72][73] TIME Magazine's 50 Genius Companies.[74] In 2019, Duolingo was named one of Forbes's "Next Billion-Dollar Startups 2019".[75]


Duolingo has received criticism for its lack of effectiveness in helping students to fully learn a language. Duolingo's CEO, Luis von Ahn, promises only to get users to a level between advanced beginner and early intermediate: "A significant portion of our users use it because it's fun and it's not a complete waste of time". 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?" after six months of Duolingo Spanish study.[1]

Language coach and podcaster Kerstin Cable have criticized the app for "its impractical vocabulary, its insistence upon one acceptable translation per sentence prompt, and its lack of explanation for incorrect answers",[76] describing Duolingo's method as "you learn by parroting phrases without even beginning to cover the background stories that grammar and pragmatics tell."[77] Linguist Steven Sacco at San Diego State University attempted to test Duolingo's claim of "34 hours of Duolingo are equivalent to a full university semester of language education"[78] by completing a course in Swedish and taking a standardized elementary exam ultimately receiving a failing grade.[76] Sacco suggested some use for Duolingo as helpful for learning vocabulary only in addition to immersion environments like a classroom.[76] Both Sacco and Cable added that Duolingo's translation method of teaching is ultimately inferior to learning a language in an immersion environment.

Duolingo also received criticism for its treatment of its courses' contributors, which work entirely on a volunteer-basis. With the company transitioning to what could be considered a more revenue-focused business approach,[79] the public backlash[80] caused many to fall out of favour with the app, and even prompted one of the contributors to the Norwegian course to leave[81] after having contributed to the course for 6 years, as well as managing the user forum and providing resources for the language, this left an in-development addition to the Norwegian course unreleased for the site's users. While the exact reason for her departure was left unspecified, a lack of respect for the volunteer work from which the site profits was mentioned. While some contributors to Duolingo's larger courses (e.g. Spanish and French for English speakers) receive a salary,[82] users speculate that the contributors' volunteer work allows for a greater degree of autonomy than that of an employee, which was subsequently threatened by Duolingo's changing business model.

In popular cultureEdit

Duolingo's mascot, a green cartoon owl named Duo, has been a subject of an Internet meme in which the mascot will stalk and threaten users if they do not keep using the app.[83] Acknowledging the meme, Duolingo released a video on April 1, 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).[84][85]

In November 2019, Saturday Night Live parodied Duolingo in a skit where adults learned to communicate with children using a fictitious course on the app titled "Duolingo for Talking to Children".[86]

See alsoEdit


  1. ^ a b Adams, Susan. "Game of Tongues: How Duolingo Built A $700 Million Business With Its Addictive Language-Learning App". Forbes. Retrieved 27 December 2019.
  2. ^ "We're thankful for our 200+ employees who have come from all around the world to help make education more accessible". Retrieved 27 December 2019.
  3. ^ Frederic Lardinois. "Duolingo hires its first chief marketing officer as active user numbers stagnate but revenue grows". Retrieved 21 November 2018.
  4. ^ "Migrating Duolingo's Android app to 100% Kotlin". blog.duolingo.com.
  5. ^ "Real World Swift – Making Duolingo Blog". making.duolingo.com.
  6. ^ a b "Rewriting Duolingo's engine in Scala – Making Duolingo Blog". making.duolingo.com.
  7. ^ https://www.duolingo.com/courses/all
  8. ^ "Duolingo moving to East Liberty, plans to add employees". The Business Journals. Retrieved 24 March 2016.
  9. ^ "100M users strong, Duolingo raises $45M led by Google at a $470M valuation to grow language-learning platform". Venture beat. 10 June 2015. Retrieved 21 June 2015.
  10. ^ "Duolingo – Learn Languages for Free". Windows phone. Microsoft. Retrieved 21 November 2014.
  11. ^ Guliani, Parul. "Duolingo Looks To Dominate The Mobile Education Market With New Flashcard App TinyCards". Forbes. Retrieved 17 February 2017.
  12. ^ Siegler, MG (12 April 2011). "Meet Duolingo, Google's Next Acquisition Target; Learn A Language, Help The Web". TechCrunch. Retrieved 21 November 2014.
  13. ^ "The Duolingo Team". Twitpic.
  14. ^ a b "When Duolingo was young: the early years". VatorNews. 22 June 2018. Retrieved 21 December 2019.
  15. ^ Mayer-Schönberger, Viktor; Cukier, Kenneth (2014). Learning with Big Data: The Future of Education. Houghton Mifflin Harcourt. pp. 9–10. ISBN 978-0-54435550-7.
  16. ^ "Immersion". duolingo. Archived from the original on 30 March 2019.
  17. ^ Olson, Parmy. "Crowdsourcing Capitalists: How Duolingo's Founders Offered Free Education To Millions". Forbes.
  18. ^ "Online Education as a Vehicle for Human Computation". National Science Foundation.
  19. ^ "Learn a language, translate the web". New Scientist.
  20. ^ Todd, Deborah M. (3 July 2012). "Ashton Kutcher backs CMU duo's startup Duolingo". Pittsburgh Post Gazette. Retrieved 13 July 2012.
  21. ^ "The Daily Start-Up: Kutcher-Backed Language Site Duolingo Finds Its Voice". The Wall Street Journal. 19 June 2012. Retrieved 13 July 2012.
  22. ^ "Series A - Duolingo - 2011-10-19". Crunchbase. Retrieved 13 December 2019.
  23. ^ Adi Robertson (16 December 2011). "Duolingo will translate the internet while teaching languages". The Verge. Retrieved 3 February 2016.
  24. ^ "We have a blog!". Official Duolingo Blog. Retrieved 14 December 2019.
  25. ^ "When Duolingo was young: the early years". VatorNews. 22 June 2018. Retrieved 14 December 2019.
  26. ^ "Duolingo Raises $15M Series B Round Led By NEA, Will Expand To More Languages And To Mobile Soon". TechCrunch. Retrieved 13 December 2019.
  27. ^ Frederic Lardinois (13 November 2012). "Language Learning Service Duolingo Launches Its First iPhone App". TechCrunch. AOL. Retrieved 18 April 2016.
  28. ^ "Duolingo – Learn Spanish, French, German, Portuguese, and Italian for free". iTunes App Store. Apple. Retrieved 29 April 2013.
  29. ^ Farber, Dan (11 July 2013). "Duolingo brings free language courses to the iPad". C net. Retrieved 21 February 2014.
  30. ^ a b c "Forum - Duolingo". forum.duolingo.com. Retrieved 14 December 2019.
  31. ^ "Series C - Duolingo - 2014-02-18". Crunchbase. Retrieved 14 December 2019.
  32. ^ "Duolingo Raises $20M Series C Led By Kleiner Perkins To Dominate Online Language Learning". TechCrunch. Retrieved 14 December 2019.
  33. ^ "Series D - Duolingo - 2015-06-10". Crunchbase. Retrieved 14 December 2019.
  34. ^ "Duolingo Raises $45 Million Series D Round Led By Google Capital, Now Valued At $470M". TechCrunch. Retrieved 14 December 2019.
  35. ^ "100M users strong, Duolingo raises $45M led by Google at a $470M valuation to grow language-learning platform". VentureBeat. 10 June 2015. Retrieved 14 December 2019.
  36. ^ "Duolingo Case Study-DynamoDB". Amazon Web Services, Inc. Retrieved 23 December 2019.
  37. ^ Duolingo Stores 31 Billion Items on Amazon DynamoDB and Uses AWS to Deliver Language Lessons, retrieved 23 December 2019
  38. ^ "Series E - Duolingo - 2017-07-25". Crunchbase. Retrieved 14 December 2019.
  39. ^ "Duolingo raises $25M at a $700M valuation". TechCrunch. Retrieved 14 December 2019.
  40. ^ a b c Duolingo. "Duolingo Now Valued at $1.5 Billion". www.prnewswire.com. Retrieved 14 December 2019.
  41. ^ Elaine, Ramirez. "Duolingo Is Launching A Korean Course To Cash In On Asia's Booming Language Market". Forbes. Retrieved 11 October 2017.
  42. ^ a b "Duolingo hires its first chief marketing officer as active user numbers stagnate but revenue grows". TechCrunch. Retrieved 14 December 2019.
  43. ^ "Duolingo raises $30 million from Alphabet's CapitalG at $1.5 billion valuation". VentureBeat. 4 December 2019. Retrieved 13 December 2019.
  44. ^ a b "Duolingo touts $1.5B valuation; language company to hire 100 more people, mostly in Pittsburgh | TribLIVE.com". triblive.com. Retrieved 15 December 2019.
  45. ^ a b Adams, Susan. "Game of Tongues: How Duolingo Built A $700 Million Business With Its Addictive Language-Learning App". Forbes. Retrieved 14 December 2019.
  46. ^ a b Luis. "Duolingo turns two today!". Retrieved 21 November 2014.
  47. ^ "Duolingo launching on Android; plans move to bigger office". Biz journals. 29 May 2013. Retrieved 21 February 2014.
  48. ^ Hartmans, Avery (23 March 2016). "Duolingo moving to East Liberty, plans to add employees". Pittsburgh Business Times. Retrieved 17 February 2017.
  49. ^ Schlosser, Kurt (14 March 2019). "Language-learning startup Duolingo looks to grow Seattle-area office in 2019". GeekWire. Retrieved 3 February 2020.
  50. ^ 张洁. "Language-learning app Duolingo bullish on Chinese market - Chinadaily.com.cn". www.chinadaily.com.cn. Retrieved 14 December 2019.
  51. ^ Doughty, Nate (8 April 2020). "Duolingo passes one million paid users, expands with new hires". Pittsburgh Business Times. Retrieved 12 December 2020.
  52. ^ Huynh, Duy; Zuo, Long; Iida, Hiroyuki (5 December 2016). Analyzing Gamification of "Duolingo" with Focus on Its Course Structure. Games and Learning Alliance. Lecture Notes in Computer Science. Springer, Cham. pp. 268–277. doi:10.1007/978-3-319-50182-6_24. ISBN 9783319501819.
  53. ^ Agomuoh, Fionna. "I've been learning French on the Duolingo app for over a year now — here's what it's like to use the app". Business Insider. Retrieved 21 January 2020.
  54. ^ VESSELINOV, ROUMEN (December 2012). "Duolingo Effectiveness Study" (PDF). Duolingo.com. Retrieved 30 May 2018.
  55. ^ Ahmed, Heba (15 June 2016). "Duolingo as a Bilingual Learning App: a Case Study". Arab World English Journal. 7 (2): 255–267. doi:10.24093/awej/vol7no2.17. ISSN 2229-9327.
  56. ^ Duolingo Incubator
  57. ^ "Duolingo: Learn Spanish, French and other languages for free". duolingo.com. Retrieved 12 April 2018.
  58. ^ "Crowdsourcing Capitalists: How Duolingo's Founders Offered Free Education To Millions". Forbes. Retrieved 22 December 2015.
  59. ^ Simonite, Tom (29 November 2012). "The Cleverest Business Model in Online Education". Technology review. Retrieved 21 February 2014.
  60. ^ a b "AWS Case Study: Duolingo". Web Services. Amazon. Retrieved 28 March 2015.
  61. ^ "Duolingo snags iPhone App of the Year". Gigaom. 17 December 2013. Retrieved 21 February 2014.
  62. ^ "Google Play reveals the most downloaded apps, games and entertainment content from 2014". The Next Web. 11 December 2014. Retrieved 29 December 2014.
  63. ^ "Duolingo-Index: Award 2015 Winner (Play & Learning Category)". Design to Improve Life. Design to Improve Life. 27 August 2015. Archived from the original on 5 May 2016. Retrieved 28 April 2016.
  64. ^ "The World's 50 Most Innovative Companies of 2018". Fast Company. Retrieved 14 December 2019.
  65. ^ "The World's Most Innovative Companies 2018: Education Honorees". Fast Company. Retrieved 14 December 2019.
  66. ^ "The World's Most Innovative Companies 2017: Education Honorees". Fast Company. Retrieved 14 December 2019.
  67. ^ "The World's Most Innovative Companies 2017: Social Media Honorees". Fast Company. Retrieved 14 December 2019.
  68. ^ "The World's Most Innovative Companies 2013: Education Honorees". Fast Company. Retrieved 14 December 2019.
  69. ^ "Duolingo". Inc.com. Retrieved 1 August 2019.
  70. ^ "Top Company Cultures of 2018". Entrepreneur. Retrieved 1 August 2019.
  71. ^ staff, CNBC.com (22 May 2018). "2018 Disruptor 50: No. 35 Duolingo". CNBC. Retrieved 5 November 2018.
  72. ^ "Duolingo: 2019 Disruptor 50 List". CNBC. Retrieved 4 September 2019.
  73. ^ Duolingo. "Duolingo Names Gillian Munson to Board of Directors". www.prnewswire.com. Retrieved 14 December 2019.
  74. ^ "Duolingo: The 50 Most Genius Companies of 2018". Time. Retrieved 5 November 2018.
  75. ^ Feldman, Amy. "Next Billion-Dollar Startups 2019". Forbes. Retrieved 20 July 2019.
  76. ^ a b c Heaney, Katie (9 July 2019). "Does Duolingo Even Work". Retrieved 28 October 2020.
  77. ^ Cable, Kersten. "It's a free app loved by millions. Is Duolingo wasting your time?". Fluentlanguage. Retrieved 27 April 2020.
  78. ^ "Are there official studies about Duolingo?". Duolingo Help Center. Duolingo. Retrieved 27 April 2020.
  79. ^ Lee, Dami (13 December 2018). "Duolingo redesigned its owl to guilt-trip you even harder". The Verge. Retrieved 15 February 2021.
  80. ^ u/Insaniaksin (2020). "I am quitting Duolingo because of the hearts system". Reddit.
  81. ^ "Forum - Duolingo". forum.duolingo.com. Retrieved 15 February 2021.
  82. ^ [citation needed]
  83. ^ Anderson, Sage. "The Duolingo owl is out for vengeance in these threatening memes". Mashable. Retrieved 7 June 2019.
  84. ^ Introducing Duolingo Push. Duolingo. 31 March 2019. Retrieved 7 June 2019.
  85. ^ "How Duolingo Took over the Meme World and What Marketers Can Learn from It". rypl.io. Retrieved 7 June 2019.
  86. ^ Lee, Madasyn (5 November 2019). "Pittsburgh-based Duolingo a fan of talk-to-kids 'SNL' sketch". Pittsburgh Tribune-Review.

External linksEdit