Duolingo, Inc. is a language-learning website and mobile application, which engages in the development of a free language learning website and crowd sourced text translation platform. It offers Duolingo for Schools, a free, web-based tool that aims to make it easier for teachers to use the Duolingo platform in a structured learning environment, and English Test, an online, on-demand assessment of English proficiency. The company was founded by Luis von Ahn and Severin Hacker in 2011 and is headquartered in Pittsburgh, PA.