LTI Client Side postMessages

This document describes the functionality of sending and receiving window postMessages used within the LTI specifications. Any messages send or received by a tool or platform should follow these rules to maintain interoperability and security whilst communicating. LTI applications are often embedded within IFrame within the Learning Platform's main window. In order to offer a more integrated experience, it is desired to establish an in-browser communication between the IFrame and its host. This can range from purely UI experience like resizing of the frame to match the actual content, to storing state outside of the frame to offer an alternative to limitations imposed by browsers on 3rd party cookies. The messaging between cross domains documents is accomplished using windows postMessage API.