In March 1989 Tim Berners-Lee presented at CERN a proposal to manage scientific information via hypertext. In December 1990 he put the first web server online. The World Wide Web transformed the internet into a navigable global information infrastructure: by combining unique identifiers (URLs), a transfer protocol (HTTP), and a markup language (HTML), it allowed anyone to publish, link, and retrieve information at planetary scale without advanced technical knowledge. Berners-Lee did not patent any of these standards, which made universal, free adoption possible. Its impact is hard to overstate: the Web is the largest library, marketplace, communication space, and social-organization tool that has ever existed.