Today marks the official launch of Unpaywall, a web browser extension that links users directly to free full-text versions of research articles. Heather Piwowar and Jason Priem of Impactstory, the team behind Unpaywall, report on the successful pre-release phase, and explain how two decades of investment, a slew of new tools, and a flurry of new government mandates have helped build a powerful momentum behind green open access
