Boot to Gecko
Boot to Gecko, or B2G, is an ambitious Mozilla project initiated to build a complete, standalone operating system for the open Web. Boot to Gecko's primary focus is for use on mobile and tablet devices as an open source mobile operating system that provides the infrastructure to build apps with Web APIs.
Boot to Gecko ultimately seeks to provide Web developers with the same capabilities as those building for operating system-specific stacks. As a result, B2G has a goal of providing mobile users all the power of HTML5 to go along with device capabilities such as SMS and Bluetooth support and a more extensive capability model for interaction with the OS filesystem, as well as a way to tie the "native HTML5 apps" together.
In June 2012 Mozilla rebranded the Boot 2 Gecko project as Firefox OS, capitalizing on the brand equity built up with the Firefox name while also following in the footsteps of Google with its Google Chrome OS.