You Have Worked for Him Without Knowing It — Luis von Ahn

Luis von Ahn speaking at Wikimania, 2015 (Wikimedia Commons, credit needed)

Have you ever typed wobbly letters to prove you are not a robot?

Those tests are called CAPTCHAs. Luis von Ahn helped invent them.

Later, he built Duolingo, the free language app with the famous green owl, used by hundreds of millions of people.

Growing up in Guatemala

Guatemala City, where Luis grew up (Wikimedia Commons, credit needed)

Luis von Ahn was born in 1978 in Guatemala City. His mother, a doctor, raised him and gave him his first computer when he was young.

He saw how expensive good education was in Guatemala. Rich families could pay to learn English. Poor families often could not. That stuck with him.

CAPTCHA and reCAPTCHA

Carnegie Mellon University, where Luis earned his PhD and teaches (Wikimedia Commons, credit needed)

Luis studied math at Duke University, then earned a PhD at Carnegie Mellon University.

There he helped create the CAPTCHA, a test to tell humans from computer bots.

Then he had a clever idea. Millions of people typed CAPTCHAs every day. What if that effort could do something useful? His next invention, reCAPTCHA, used those typed words to help digitise old books and newspapers.

In 2006, he won a MacArthur "genius grant." In 2009, Google bought reCAPTCHA.

Duolingo

The Duolingo homepage and logo (Wikimedia Commons, credit needed)

Luis wanted to use technology to give everyone free education. With his PhD student Severin Hacker, he founded Duolingo in Pittsburgh. It launched in 2012.

Duolingo made learning feel like a game, with streaks, points and cheerful reminders from Duo the owl. Its free version stayed free, while paid subscriptions supported the business.

On July 28, 2021, Duolingo went public on the Nasdaq.

Duolingo merchandise featuring Duo the owl (Wikimedia Commons, credit needed)

AI and new subjects

In 2025, Luis announced Duolingo would be "AI first," which caused backlash from some users worried about jobs. Duolingo also expanded beyond languages into math, music and chess.

In 2026, Luis was named the recipient of the IEEE Frances E. Allen Medal.

Where he is now

Today, Luis von Ahn is co-founder and CEO of Duolingo. He also serves on the board of Figma.

Why the story matters

Luis von Ahn's story shows that small actions from many people can do huge things, and that free can still be a strong business.

For young builders, the lesson is simple. Look for hidden value in everyday behaviour, and build products that are good for people and fun to use.

He turned squiggly letters into books, and practice into play.

The Record

Born: 1978

From: Guatemala City, Guatemala

Studied: B.S. Mathematics, Duke; PhD Computer Science, Carnegie Mellon

Built: CAPTCHA (co-inventor), reCAPTCHA, Duolingo (with Severin Hacker)

Timeline

1978 Born in Guatemala City.

2000s Co-invents the CAPTCHA at Carnegie Mellon.

2006 Wins a MacArthur Fellowship.

2009 Sells reCAPTCHA to Google.

2012 Launches Duolingo.

2021 Duolingo goes public on the Nasdaq.

2025 Announces AI first strategy.

2026 Named IEEE Frances E. Allen Medal recipient.