# Duolingo

Duolingo, Inc. is an American educational technology company that produces learning apps and provides language certification. Duolingo offers courses on 43 languages, ranging from English, French, and Spanish to less commonly studied languages such as Welsh, Irish, and Navajo, and even constructed languages such as Klingon. It also offers courses on music and math. The learning method incorporates gamification to motivate users with points, rewards and interactive lessons featuring spaced repetition. The app promotes short, daily lessons for consistent-phased practice.
Duolingo also offers the Duolingo English Test, an online language assessment, and Duolingo ABC, a literacy app designed for children. The company follows a freemium model, with optional premium services like Super Duolingo and Duolingo Max, which are ad-free and provide additional features. Additionally, Duolingo runs Duo's Taqueria, a Mexican taco restaurant in Pittsburgh.
With over 110 million monthly active users, Duolingo is the most popular educational app in the world. Over 10 million people have a Duolingo streak longer than a year. In total, learners on Duolingo complete more than 13 billion exercises per week. A systematic review of research on Duolingo from 2012 to 2020 found comparatively few studies on the platform's efficiency for language learning but identified several studies that reported relatively high user satisfaction, enjoyment, and positive perceptions of the app's effectiveness. The company has also been recognized for its successful marketing tactics and strong brand engagement.

## History
### 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. Hacker (co-founder and current CTO of Duolingo) believed that "free education will really change the world" and wanted to provide an accessible means for doing so. He was recognized by the National Inventors Hall of Fame for his contributions to language learning and technological development. 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. Its early revenue stream, a crowdsourced translation service, was replaced by a Duolingo English Test certification program, advertising, and subscription.

### Funds

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. 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; it later reported a figure closer to 60 million users.
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. 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. In March 2021, it announced that it would be ending its volunteer contributor program and donating money to its volunteer contributors who helped develop it. The company said that from now on, language courses would 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 the early 2020s, Duolingo was noted for its viral videos on the social media platform TikTok.
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 Twitter. CEO Luis von Ahn stated that there were no plans to reverse the changes—intended to simplify Duolingo for its new users—maintaining both the old and new versions would be difficult. In October 2022, Duolingo acquired Detroit-based animation studio Gunner; it is the studio that produces art assets and animation for Duolingo and Duolingo ABC and its marketing campaigns.
In March 2023, Duolingo officially announced the planned Duolingo Max, a subscription tier above Super Duolingo, in their blog. In July 2023, Duolingo launched a feature using the iOS widget feature. In October 2023, Duolingo released math and music courses in English and Spanish for iOS users.
In 2024, Duolingo made several changes: it replaced some contractor tasks with AI in January, launched the widget feature on Android in March, acquired Detroit-based design studio Hobbes, introduced Friend Streak in August, allowing students to share a streak together with their friends, and released math and music courses for Android in September. During Duocon 2024, Duolingo introduced various new features, including Video Call and mini games called Adventures. In October Duolingo introduced Duolingo Score.
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.

## Products and services
### Courses
#### Language courses

Duolingo has 184 language courses teaching 42 languages.
Duolingo languages :
| For speakers of | Language course |
| Arabic | English, French, German, Italian, Spanish, Swedish |
| Bengali | English, French, German, Italian, Spanish |
| Chinese (Mandarin) | Chinese (Cantonese), English, French, German, Italian, Japanese, Korean, Spanish |
| Czech | English, French, German, Italian, Spanish |
| Dutch | English, French, German, Italian, Spanish |
| English | Arabic, Chinese (Mandarin), Czech, Danish, Dutch, English (Intermediate), Esperanto, Finnish, French, German, Greek, Haitian Creole, Hawaiian, Hebrew, High Valyrian, Hindi, Hungarian, Indonesian, Irish, Italian, Japanese, Klingon, Korean, Latin, Navajo, Norwegian, Polish, Portuguese, Romanian, Russian, Scottish Gaelic, Spanish, Swahili, Swedish, Turkish, Ukrainian, Vietnamese, Welsh, Yiddish, Zulu |
| French | English, German, Italian, Portuguese, Spanish |
| German | English, French, Italian, Spanish |
| Greek | English, French, German, Italian, Spanish |
| Hindi | English, French, German, Italian, Spanish |
| Hungarian | English, French, German, Italian, Spanish |
| Indonesian | English, French, German, Italian, Spanish |
| Italian | English, French, German, Spanish |
| Japanese | Chinese (Mandarin), English, French, German, Italian, Korean, Spanish |
| Korean | English, French, German, Italian, Spanish |
| Polish | English, French, German, Italian, Spanish |
| Portuguese | English, French, German, Italian, Spanish |
| Romanian | English, French, German, Italian, Spanish |
| Russian | English, French, German, Italian, Spanish |
| Spanish | Catalan, English, French, German, Italian, Portuguese, Russian, Swedish |
| Swedish | English, French, German, Italian, Spanish |
| Tagalog | English, French, German, Italian, Spanish |
| Tamil | English, French, German, Italian, Spanish |
| Telugu | English, French, German, Italian, Spanish |
| Thai | English, French, German, Italian, Spanish |
| Turkish | English, French, German, Italian, Russian, Spanish |
| Ukrainian | English, French, German, Italian, Spanish |
| Vietnamese | Chinese (Mandarin), English, French, German, Italian, Spanish |

#### Duolingo Math

Duolingo Math is an app course for learning elementary mathematics. It was announced on YouTube on August 27, 2022, at the Duocon 2022 event. Duolingo Math covers math topics through an interactive and gradual approach. It starts with basic arithmetic—addition, subtraction, multiplication, and division. The app also teaches fractions and decimals, focusing on comparing, converting, and calculating. Geometry lessons include understanding shapes, calculating area and volume. Measurement is another focus, with exercises on using and converting different units like length and time. Duolingo also allows its users to play math games.

#### Duolingo Music

In March 2023, Duolingo was reportedly developing a new music course that would allow users to learn how to read and play music through its gamified learning experience. On October 11, 2023, Duolingo formally unveiled Duolingo Music in a YouTube Short, a new platform within the existing app that provides basic music learning through piano and sheet music lessons. As of April 2024, it is currently available on iOS and Android devices. Since August 2024, users can practice music by playing pop songs in the course.

### Subscriptions
#### Super Duolingo

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. This program, known as Super Duolingo (formerly known as Duolingo Plus), includes benefits such as unlimited hearts (retries), personalized practice, no ads, focused listening and speaking exercises, free and unlimited entries to legendary challenges, side quests and play pop songs (you can play them for free), and 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; 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. Intended to provide further immersion through "free-flowing conversation", it is available in selected courses and markets.

### 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 ABC

Duolingo ABC 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.

### Duolingo x Loog Piano

The Duolingo x Loog Piano is a 37-key portable digital piano created through a partnership between Duolingo and Loog. It features velocity-sensitive keys, built-in speakers, and ports for USB-C, a sustain pedal, and headphones. The piano is designed to work with Duolingo's music lessons.

### 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. The test's certificate is reportedly accepted by over 5,500 programs internationally, albeit with exceptions.

## 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 worldwide player 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.
Duolingo has a widget feature on iOS and Android. The widget feature initially started as Duolingo's annual hackathon project. The iOS widget has 39 illustrations designed by Kyle Ruane that were intended to be another daily reminder to complete lessons. On the top part of the widgets is the user's daily streak. 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".
Any lesson completed in Duolingo will count towards the user's daily streak. The daily streak's visual symbol in the app is fire. Duolingo's "Friend Streak" lets users maintain streaks with up to five friends. 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 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.
| Duolingo Score | CEFR level | Student can... |
| 0–9 | very early A1 | use simple words and phrases in some common scenarios |
| 10–19 | early A1 | talk about themselves and where they live and ask and answer simple questions |
| 20–29 | high A1 | discuss their daily routine, order food at a restaurant, and chat a little |
| 30–59 | A2 | have basic conversations about familiar topics, including weather, shopping, hobbies, and holiday plans |
| 60–79 | early B1 | handle common situations while traveling, ask for directions, and make reservations |
| 80–99 | high B1 | share their opinion, tell stories, and navigate most daily situations |
| 100–114 | early B2 | have deep discussions about their interests and understand news, movies, and jokes |
| 115–129 | high B2 | express themselves in most situations and uses the language in professional and academic scenarios |
| 130–160 | C1 and C2 | easily understand all that they hear or read and expresses nuanced thoughts in sophisticated language |

## 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 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 2024 Duolingo has 8 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, and $1 million in 2016. In May 2022, it was reported that 6.8% of its monthly active users paid for the ad-free version of the app.

## 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.
A 2022 study on adults using Duolingo as their only language learning tool, published in the journal Foreign Language Annals, found that participants who completed a course had similar reading and listening proficiency to university students after four semesters of study, concluding that Duolingo could be an effective tool for language 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. Players have also reported that "gamification" has led to cheating, hacking, and incentivized game strategies that conflict with actual learning.
In March 2022, Duolingo forums were discontinued, and Sentence discussions became read-only. The change has been criticized on some social media sites.
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's "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. Duolingo courses vary greatly in quality. While most popular language courses like Spanish or French are well developed, other courses for less studied languages like Ukrainian or Guarani cover very little grammar and vocabulary.

### Awards

In 2013, Apple chose Duolingo as its iPhone App of the Year, a first for an educational application. That year, Duolingo ranked No. 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". Duolingo won Best Education Startup at the 2014 Crunchies, and was the most downloaded 'education app' in Google Play in 2013 and 2014. In July 2020, PCMag named it "The Best Free Language Learning App".
As a company, Duolingo has likewise won several awards and recognitions. In 2015, it was announced as that year's Index Award winner in the Play & Learning category by The Index Project. It won Inc. magazine's Best Workplaces 2018, made Entrepreneur magazine's Top Company Culture List 2018, was among CNBC's "Disruptor 50" lists for 2018 and 2019, and was ranked as one of TIME magazine's 50 Genius Companies. Duolingo was named one of Forbes's "Next Billion-Dollar Startups 2019". In 2023, Duolingo won a Design Award during the 2023 edition of the Apple Design Awards.

## Image and brand
### Duolingo's characters

Duolingo has brand characters that are used for engagement and creating storylines. The main characters include:
* Beatrice "Bea" Boateng: Born on January 1, 2000, Bea is a smart and energetic young girl.
* Duo Keyshauna Renee Lingo: Commonly known as Duo or Duo the Owl, he is 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 XP 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 bit of a 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.
* Eddy: An optimistic character with a passion for sports, father of Junior.
* Falstaff: An older, intellectual grizzly bear with a love for literature.
* Junior: A curious and eager young boy.
* Lily: A teenager girl known for her sarcastic, emo, and indifferent personality, often expressing a lack of enthusiasm but secretly caring about her friends. She is one of the main characters in Duolingo’s cast of mascots used in video call feature.
* Lin: A creative and adventurous artist and motorcyclist.
* Lucy: A venturesome elderly lady, grandmother of Lin.
* Oscar: A high school teacher and a prim connoisseur of art and culture.
* Vikram: A calm and responsible professional.
* Zari: A confident and enthusiastic Middle Eastern teenage girl. She dresses in pink and blue and wears a headscarf/hijab. She is Lily's best friend.
All characters mentioned above are human, with the exceptions of Duo, who is an owl, and Falstaff, who is a bear.

### 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 antagonising 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 February 2020, as part of the company's partnership with the developers of the video game Angry Birds 2, a skit depicting Duo and the red Angry Bird attacking a crowd was uploaded.
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.
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".
The 2023 film Barbie contains a running gag where the husband of disgruntled Mattel employee Gloria uses Duolingo to learn Spanish, Gloria's native language.

### Duocon

Duocon is Duolingo's annual conference, launched in 2019, aimed at gathering Duolingo users, language enthusiasts, and educational technology professionals. 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.
The inaugural Duocon in 2019 featured presentations from Duolingo's team, interactive sessions, and announcements about new developments. The 2020 event was adapted to a virtual format due to the COVID-19 pandemic. Subsequent events have also been held online.

## Duo's Taqueria

Duo's Taqueria is a taqueria (a Mexican taco restaurant) in Pittsburgh, Pennsylvania, operated by Duolingo. The taqueria offers a variety of authentic Mexican tacos and other traditional dishes. The restaurant encourages patrons to order in Spanish, aligning with Duolingo's mission of making language learning fun and accessible. Duolingo's taco shop brought in $700,000 in 2023.

## Offices and workforce

Duolingo is headquartered in Pittsburgh, Pennsylvania, and has offices in Seattle, New York, Detroit, Beijing, and Berlin.
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. The gallery showcases moving images of Duo and other characters in a range of artistic styles.
Duolingo employs around 830 people.