MRAID, or “Mobile Rich Media Ad Interface Definitions” is the IAB Mobile Marketing Center of Excellence’s project to define a common API (Application Programming Interface) for mobile rich media ads that will run in mobile apps. This is a standardized set of commands, designed to work with HTML5 and JavaScript, that developers creating rich media ads use to communicate what those ads do (expand, resize, get access to device functionalities such as the accelerometer, etc) with the apps into which they are being served.