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Duolingo logo
Web address .comduolingo
Slogan Free language education for the world
Type of site Online education, Translation, Crowdsourcing
Registration Free
Available in
Launched 30 November 2011 (2011-11-30)
Current status Public

Duolingo is a free language-learning and crowdsourced text translation platform. The service is designed so that, as users progress through the lessons, they simultaneously help to translate websites and other documents.[1][2] As of 14 September 2014, Duolingo offers Latin American Spanish, French, German, Brazilian Portuguese, Italian, Dutch, Danish, Irish and Swedish courses for English speakers, as well as American English for Spanish, French, German, Portuguese, Italian, Dutch, Russian, Polish, Turkish, Hungarian, Romanian, Japanese, Hindi, Indonesian, Korean and Czech speakers. It also offers many other combinations of languages.[3] It is available on the Web, iOS, Android and Windows Phone 8.1 platforms.[4]

Duolingo started its private beta on 30 November 2011 and accumulated a waiting list of more than 300,000 users.[5] Duolingo launched for the general public on 19 June 2012 and as of January 2014 has 25 million users, out of which about 12.5 million are active.[6][7] In 2013, Apple chose Duolingo as its iPhone App of the Year, the first time this honor was awarded to an educational application.[7] Duolingo won Best Education Startup at the 2014 Crunchies.[8]

Education model

Duolingo offers extensive written lessons and dictation, but it features less speaking practice. It has a gamified skill tree that users can progress through and a vocabulary section where learned words can be practiced.
A screen-shot from the English to French Duolingo

Users gain "experience points" (XP) as they learn a language, such as when they complete a lesson. Skills are considered "learned" when users complete all the lessons associated with the skill. Users win one point for each correct answer, and lose one for each error, and validate the lesson when they reach 10 points. (Users used to start with four "lives" on early lessons and three on later lessons, a "life" being lost with each mistake, in an earlier version). Duolingo also includes a timed practice feature, where users are given 30 seconds and twenty questions and awarded a skill point and seven or ten additional seconds (time depends on the length of the question) for each correct answer.[9] Courses can teach upwards of 2,000 words.[10]

Duolingo uses a heavily data-driven approach to education.[11] At each step along the way, the system measures which questions the users struggle with and what sorts of mistakes they make. It then aggregates those data and learns from the patterns it recognizes.

The efficacy of Duolingo's data-driven approach has been reviewed by an external study commissioned by the company. Conducted by professors at City University of New York and the University of South Carolina, the study estimated that 34 hours on Duolingo may yield reading and writing ability of a US first-year beginners' course college semester, which takes in the order of 130+ hours. The research did not measure speaking ability. It found that a majority of students dropped out after less than 2 hours of study.[12] The same study found that Rosetta Stone users took between 55 and 60 hours to learn a similar amount.[13] The study did not compare Duolingo to other free or inexpensive courses, such as BBC,[14] Book2,[15] or Before You Know It.

Business model

Duolingo does not charge students to learn a language. Instead, it employs a [16] On 14 October 2013, Duolingo announced it had entered into agreements with CNN and BuzzFeed to translate articles for the companies' international sites.[17][18]

The Language Incubator

Instead of slowly adding additional languages, CEO Luis von Ahn announced on 29 May 2013 that they would create the tools necessary for the community to build new language courses, with the hope to introduce more languages and "empower other experts and people passionate about a specific language to lead the way".[19] The result was The Language Incubator, which was released on 9 October 2013.[20][21] In addition to helping the community create courses for widely spoken languages, the Duolingo Incubator also aims to help preserve some of the less popular languages such as Latin, Mayan and Basque.[22] The first course entirely created by the Duolingo community through the Incubator was learning English from Russian, which launched in beta on 19 December 2013.[23] Other courses created by the Duolingo community include English from Turkish, Dutch and Hungarian, as well as French and Portuguese from Spanish.

The Incubator has three Phases. First, a language begins in "Phase 1: Not Yet Released," once sufficient interest to contribute to the program has been received from volunteers fluent in both languages (a requirement for application). The second phase, "Phase 2: Released in Beta," begins when the course has been fully prepared and is ready for open beta testing. Finally, "Phase 3: Graduated from Beta" is where all courses available offerings go once they are considered relatively stable. The reason complete courses remain in the incubator is that Moderators/Contributors can continue to tweak things to improve the course. For example, if a student gets a question wrong but notices there was an error on the program's behalf, which either misled the student or counted a correct answer wrong, s/he may submit a report detailing what happened. As of November 8, 2014, eight courses are currently available to the public from/in English: (in Incubator Phase 3) Spanish, French, German, Italian, Portuguese, Dutch (in beta), Irish (in beta), Danish (in beta) and Swedish (in beta). Coming soon to the English speaking world (in order of progression percentage towards completion): Turkish (94%), Hungarian (89%), Esperanto (47%), Russian (43%), Ukrainian (23%), Polish (10%), and Romanian (8%).[24][25][26]

Usually, a course teaching English from another language will be made before the reverse (a course teaching that language for English speakers). Once that course reaches Phase 3, the course for English speakers is started, supposedly with much of the work already done. Exceptions to this rule are when a language has few speakers and/or most speakers already know English, e.g. Irish. Courses teaching English for speakers of Chinese, Arabic, Vietnamese, Greek, Indonesian, Japanese, Hindi and Korean are in Phase 2, at about 90% each. The English for Czech speakers course is also in Phase 2, but at about 10-12%, and the English for Thai speakers course is in Phase 1 at 76.8%. Therefore, it is relatively safe to assume that all of these languages will have courses teaching them for English speakers at some point in time.[24]


The project was started in Pittsburgh by Carnegie Mellon University professor Luis von Ahn (creator of reCAPTCHA) and his graduate student Severin Hacker, and then developed also with Antonio Navas, Vicki Cheung, Marcel Uekermann, Brendan Meeder, Hector Villafuerte, and Jose Fuentes.[1][27] The project was originally sponsored by Luis von Ahn's MacArthur fellowship and a National Science Foundation grant[28][29] and is mainly written in the programming language Python.[30] Additional funding was later received in the form of an investment from Union Square Ventures and actor Ashton Kutcher's firm A-Grade Investments.[31][32]

As of 19 June 2014, Duolingo had 32 staff members and operates from an office in the Pittsburgh neighborhood of Shadyside near Carnegie Mellon's campus.[8][33]

As of 2 June 2014, Duolingo has reached 30 million users.[8]

On 13 November 2012 Duolingo released their iOS app through the iTunes App Store.[34] The app can be downloaded for free and is compatible with most iPhone, iPod and iPad devices.[35] On 29 May 2013, Duolingo released their Android app, which was downloaded over a million times in the first three weeks and quickly became the #1 education app in the Google Play store.[36] Duolingo released both a Google Glass App (glassware) and support for Android Wear.[37] A visual history can be found here.

Levels and user experience

Users are placed at a certain level in the program, corresponding to how much they have studied that language. A user's level is indicated by a number displayed on a medallion which contains a depiction of the flag of the country where that language is spoken. The levels of all languages any user is studying are displayed publicly to other users next to their username. In order to level-up, a student/user must either earn sufficient points by progressing through the Duolingo lessons, or by translating actual documents and earning a set rate of points-per-word (which increases with each Translation Tier they belong to in that language). Lessons typically comprise 14-20 questions/sentences and last between 4–7 minutes. Each completed lesson earns 10 experience points (XP) plus a bonus for any remaining hearts at the end of the lesson. In order to reach the next level, acquiring a set threshold of points is required and the points-per-level increases with each level. At least 25 levels in each language exist.

As the goal of Duolingo is to get people to learn the language, each unit (containing between 1 to 10 lessons in each) has a "strength bar" which corresponds to the computer's estimate of how strongly certain words or constructions still exist in the user's memory. After a certain duration of time, strength bars fade, indicating a need for a user to refresh/re-study that lesson, or to "strengthen weak skills." Doing "Real-World Translation," however, also strengthens words, as the program keeps track of all words a user encounters when using the "Immersion" option to translate actual documents from the internet.

See also


  1. ^ a b MG Siegler (April 12, 2011). "Meet Duolingo, Google's Next Acquisition Target; Learn A Language, Help The Web". TechCrunch. Retrieved 2014-11-21. 
  2. ^ Christopher Mims (May 2, 2011). "Translating the Web While You Learn". Technology Review. Retrieved 2014-11-21. 
  3. ^ "Duolingo: Language Courses". Retrieved 26 August 2014. 
  4. ^ "Duolingo - Learn Languages for Free". Retrieved 2014-11-21. 
  5. ^ "We have a blog!". Duolingo Blog. 
  6. ^ "LUIS VON AHN ON DUOLINGO'S PLANS FOR 2014". Crowdsourcing. 
  7. ^ a b "Duolingo snags iPhone App of the Year". 2013-12-17. Retrieved 2014-02-21. 
  8. ^ a b c Luis. "Duolingo turns two today!". Retrieved 2014-11-21. 
  9. ^ "Ready, Set, Practice!". Duolingo Blog. Retrieved 8 November 2012. 
  10. ^ My Three Months of Duolingo: "There are 2014 words listed in my Duolingo vocabulary". ( 2012-09-19)
  11. ^ "Duolingo's Data-Driven Approach to Education". 2013-01-31. Retrieved 2014-02-21. 
  12. ^ "Duolingo Effectiveness Study". unpublished. Retrieved 2013-08-23. 
  13. ^ Kelleher, Kevin (2013-05-30). "Say what? Duolingo points to data's important role in online education". Retrieved 2014-02-21. 
  14. ^ "BBC Languages". BBC. Retrieved 2013-08-23. 
  15. ^ "book2 - Learn languages online for free with 100 audio (mp3) files". Goethe-Verlag. Retrieved 2013-08-23. 
  16. ^ Simonite, Tom (2012-11-29). "The Cleverest Business Model in Online Education". Retrieved 2014-02-21. 
  17. ^ "Duolingo now translating BuzzFeed and CNN". Duolingo. 14 October 2013. Retrieved 7 November 2013. 
  18. ^ "BuzzFeed Expands Internationally In Partnership With Duolingo". BuzzFeed. 14 October 2013. Retrieved 7 November 2013. 
  19. ^ von Ahn, Luis. "Reddit IAmA". Retrieved 3 June 2013. 
  20. ^ Olson, Parmy. "Duolingo Takes Online Teaching To The Next Level, By Crowd Sourcing New Languages". Forbes. 
  21. ^ "Discussion". Duolingo. Retrieved 9 October 2013. 
  22. ^ "Duolingo 'incubator' aims to crowdsource language teaching". 2013-10-15. Retrieved 2014-02-21. 
  23. ^ "English from Russian is now available in beta!". Retrieved 2014-02-21. 
  24. ^ a b
  25. ^
  26. ^
  27. ^ "The Duolingo Team". Twitpic. 
  28. ^ "Online Education as a Vehicle for Human Computation". National Science Foundation. 
  29. ^ "Learn a language, translate the web". NewScientist. 
  30. ^ "What language is Duolingo written in?". Quora. Retrieved 2014-02-21. 
  31. ^ Todd, Deborah M. (3 July 2012). "Ashton Kutcher backs CMU duo's startup Duolingo". Pittsburgh Post Gazette. Retrieved 13 July 2012. 
  32. ^ "The Daily Start-Up: Kutcher-Backed Language Site Duolingo Finds Its Voice". Wall Street Journal. 19 June 2012. Retrieved 13 July 2012. 
  33. ^ "Duolingo launching on Android; plans move to bigger office". 2013-05-29. Retrieved 2014-02-21. 
  34. ^ "Duolingo on the go. Our iPhone App is here!". Duolingo. 13 November 2012. Retrieved 27 November 2012. 
  35. ^ "Duolingo - Learn Spanish, French, German, Portuguese, and Italian for free". iTunes App Store. Apple. Retrieved 29 April 2013. 
  36. ^ Farber, Dan (2013-07-11). "Duolingo brings free language courses to the iPad". Retrieved 2014-02-21. 
  37. ^

External links

  • Official website
  • Official blog
  • Duolingo on Twitter
  • Duolingo on Facebook
  • Duolingo Intro on YouTube
  • Luis von Ahn: Massive-scale online collaboration on YouTube — by "TEDtalksDirector" channel, uploaded 2011-12-06.
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