The service was bought by Google and became the basis for Google Image Search

[Joywtome231]

To get into university, Luis had to fly to neighboring El Salvador to take a language test. It cost his family a huge amount of money - $1,200. It was then that he first began to think about how unwieldy the language test system was and how many talented young people were losing their chance to make it in life because they couldn't pass the test.

Luis was lucky: he passed his test, which allowed him to start studying in the United States. There, at Carnegie Mellon University, he created CAPTCHA technology together with Manuel Blum. It was immediately adopted by the then popular Yahoo! service. However, this invention did not bring in any money.

The idea of ​​CAPTCHA, however, led him to explore what he called “human kazakhstan phone number list computation,” the first to apply the term to problem-solving methods that combine the human brain and a computer. Using this technology, he created the ESP game, in which people helped a computer learn to recognize images.
The second product that Google also acquired from Louis was reCAPTCHA, an improved version of CAPTCHA that, instead of a meaningless string of letters, used text from books to digitize it.

In 2009, when Louis had money, contacts and experience in creating commercially successful IT products, he decided to return to the long-standing question that he so wanted to solve. Together with his graduate student Severin Hacker, he began creating a platform that would make language learning simple and accessible to everyone. The platform was called Duolingo.

How Duolingo the Owl Took Over the World
Louis and Severin had a good understanding of how to create IT products and understood their marketing. However, this was not enough to launch a language learning app. To prevent Duolingo from becoming another boring and unpopular service, the scientists had to analyze a lot of textbooks and practical manuals for those who learn and teach foreign languages.