Duolingo raises $15M for language learning and crowdsourced translation

Computer scientist and entrepreneur Luis von Ahn has already put the crowd to work identifying images online and digitizing books. Now, the founder of ESP Game (which became Google Image Labeler (s GOOG)) and Recaptcha is determined to get them to translate the entire web – while they learn a new language.

Founded last year, Duolingo is a free online service that helps people learn languages while also translating real-world content from the web.  The platform opened to the public this summer and, on Monday, is announcing that it has raised $15 million in Series B funding. The round was led by New Enterprise Associates and included current investor Union Square Ventures. Last year, the company raised $3.3 million from Union Square Ventures and others.

“The goal has been to translate the whole web into every major language,” said von Ahn, who is co-founder and CEO of Duolingo.

With the new funding, he said, they plan to hire more engineers and expand their language options.  Currently, Duolingo supports those who want to learn English, Spanish, French, German and Portuguese, but they plan to add Chinese and Italian later this year. Von Ahn said they also plan to localize the site for more users around the world.  For example, while those who speak English and Spanish can learn each of the other languages, those who are primary French speakers don’t have the same flexibility.  Giving international users more choice is a priority, Ahn said. Later this year, Duolingo also plans to release an iPhone app.

Since launching out of private beta in June, the site has attracted about 250,000 active users, who log into the platform for 30 minutes every day. As people learn a new language, the platform serves up new content that is most appropriate to their level of competence.  For now, Duolingo learners are translating Creative Commons documents, von Ahn said, but they are in pilot programs with three major news sites.

People also have the option to upload their content to the site to have the Duolingo community translate it for free. Down the road, von Ahn said, the company could charge for translation services that require speed and accuracy.

Von Ahn, who sold both ESP and Recaptcha to Google, estimates that 1.2 billion worldwide are learning a foreign language. Tapping into that market while harnessing their collective work for translation is an interesting and big opportunity, especially considering that 50 percent of the web is only in English.