This talk is about a prototype that enables collaborative mapping without the need of any internet connectivity, only a local network is required. It runs fully in the browser, hence is cross-platform, it basically runs on any smartphone. The users form a peer-to-peer network in order to exchange their data. It can be used in situations where there either is no internet infrastructure, it's spotty or it was destroyed. In the disaster response case, only a local network, without any server infrastructure, would be needed. In the talk you'll learn about content-addressing, WebRTC and peer-to-peer networks and of course experience a live demonstration of the prototype.