reCAPTCHA and Duolingo: Luis von Ahn

The 'How I Built This' episode with Luis von Ahn explores his journey from creating CAPTCHA and reCAPTCHA to founding the language-learning app Duolingo. Born in Guatemala, Luis spent his childhood playing with machines at his family's candy factory and excelling in mathematics. His proficiency in math led him to a PhD program at Carnegie Mellon, where he attended a lecture that inspired him to solve a significant problem for Yahoo: distinguishing human users from bots. Along with his advisor, Luis developed CAPTCHA, a system that uses distorted text to verify human users, which he provided to Yahoo for free. This innovation was quickly adopted across the internet. Luis's next venture was reCAPTCHA, a refined version of CAPTCHA that also helped digitize books by having users transcribe words that computers couldn't recognize. This project was profitable and eventually acquired by Google. However, Luis's passion for accessible education led him to leave Google and start Duolingo with his student, Severin Hacker. They aimed to provide free language education, using a business model that involved users translating content as they learned. Duolingo gained significant traction, especially after the launch of its mobile app, but faced challenges in monetizing without compromising its mission. The episode details the company's eventual shift towards a freemium model, incorporating ads and a subscription service to become financially sustainable.