Cobalt is a free and open source metaverse browser and construction toolkit for accessing, creating, and publishing hyperlinked multi-user virtual worlds. Powered by Croquet technology, Cobalt uses peer-based messaging to eliminate the need for virtual world servers and makes it very simple to create and securely share deeply collaborative virtual worlds that run on all major software operating systems. Without any licensing fees, users and developers can freely build and share highly capable multi-user virtual workspaces, game-based learning and training environments, or even just a place to share and meet with friends.