In April 2020, the federal government and the state premiers backed a design for the German coronavirus warning app that would store contact data centrally. On 24 April 2020, the Chaos Computer Club, the German Informatics Society and other organizations published an open letter to the government: Das von Ihnen präferierte Konzept für die App ist nicht der richtige Weg. (The concept you prefer for the app is not the right way.) In the night to 26 April, the government gave in. That morning it said it now preferred a decentralized approach, with contacts stored only on the phones. Linus Neumann, one of the Chaos Computer Club’s spokespeople, called it a sehr gute Entscheidung, a very good decision. The source code was published openly in May. The app was released on 16 June 2020, and it had 6.5 million downloads by the next day.