In March 1989, Tim Berners-Lee, while working at CERN, released his proposal for a new information-management system. Within two years, the web was born. CERN's subsequent agreement in 1993 to place the underlying software in the public domain (reproduced in this issue) shapes the web's character to this day.
It is part of a culture of sharing and collaboration that was set out in the CERN Convention 40 years earlier, and which is deeply engrained in the software and particle-physics worlds. The features in this issue - from open-source software, to open-access publishing, open data and entirely open analysis procedures - show how far ahead our field is in the growing open-science movement. Our Viewpoint, meanwhile, argues that we have only begun to harness the full potential of the web to benefit humanity.