This document describes Moodbile, a Moodle web services extension for mobile applications. It was created to address the lack of mobile optimization in Moodle's user interface and to support increasing mobile access. Moodbile adds two layers to Moodle's architecture: an external API layer that implements services for mobile integration like courses, content, and users, and a web services connector layer that supports protocols like JSON, JSONP and REST. It also addresses authentication using OAuth to allow for mobile access without IP restrictions. Moodbile clients have been created for HTML5, Android and iOS platforms.