The web went live in 1991 but for two years remained largely an instrument of physicists and academic networks. The browsers of the day were text-based, awkward to install, and mostly tied to a single operating system. Mosaic, written at NCSA (the National Center for Supercomputing Applications) by Marc Andreessen and Eric Bina, changed three things: it placed images inline with text, reduced installation to a single file, and shipped Unix, Windows and Macintosh versions together. It was free, and its source was distributed under an academic licence.

The result was an explosion in use: the number of web servers went from roughly a hundred in early 1993 to thousands by the end of that year and tens of thousands by 1995. With Netscape Navigator, from the company Andreessen founded the following year, the browser became the interface of the commercial internet; its rivalry with Microsoft's Internet Explorer ended in an antitrust case at the close of the decade.

The lasting effect was cultural rather than technical. Once the page became a format anyone could publish in, the gatekeepers of publishing — the press, the distributor, the broadcast licence — were bypassed. Personal pages, forums, search engines and eventually social networks all grew on that footing. What we now call digital culture — text of uncertain provenance travelling fast, amateur production made visible, an archive that can be searched — largely took shape in the space this graphical interface opened. Tim Berners-Lee's contribution was to create the protocol; Mosaic's was to make it clickable.