Duolingo

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. Von Ahn had sold his second company, reCAPTCHA, to Google and, with Hacker, wanted to work on something related to education. 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. Swiss-born Hacker believed that "free education will really change the world" 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. The founders considered creating Duolingo as a nonprofit organization but Von Ahn judged this model as unsustainable. 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.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 27, 2011, and accumulated a waiting list of more than 300,000 people. The platform 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 an Android app in May 2013, at which time Duolingo had a user base of around 3 million. By July 2013, the service had grown to 5 million users and was rated the #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, Duolingo had 34 employees and reported having about 25 million registered users and 12.5 million active users, though 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 1 August 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. Headcount at the company had increased to 200, 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.In October 2013, Duolingo launched a crowdsourced language incubator. 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. The company said that from now on, language courses will be maintained and developed by professional linguists aligning with CEFR standards. On 28 June 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 their viral videos on the social media platform TikTok.In August 2022, Duolingo overhauled its user interface and user experience, changing the structure of the courses from a tree-like design where users could choose from a range of lessons after completing previous ones, to a linear progression. This was widely criticized by users across a variety of social media outlets, including Reddit and Twitter. CEO Luis von Ahn said that they had no plans of undoing the changes, commenting that their decision was made in order to simplify Duolingo for new users, and that maintaining both the old and new versions would be difficult.In October 2022, Duolingo acquired Detroit-based animation studio Gunner.