OSA: a lens to make digital visible

Digital technologies are adopted every day by people, firms and public bodies, yet their effects on sustainability remain largely invisible at the moment of decision. This method note presents OSA, a simple qualitative lens that reads any digital solution against what came before it. A solution may Optimise an existing activity, Substitute it, or Amplify it, or it may change nothing, a zero point that marks the boundary of the lens and exposes broken promises. Each reading is made for whom: the same technology can improve conditions for one actor and worsen them for another. Five roles structure this analysis: who decides, who uses it every day, who receives it, who comes after, and who supplies it. The note links OSA to the literature on substitution and generation effects, automation and augmentation, orders of ICT effects and rebound, and the social shaping of technology. It describes recurring patterns, application steps and limits, and offers OSA as a shared starting point for teaching, case collection and decision support.