Echo is a free Chrome add-on developed by Jacky Gao. It falls under the category of Browsers and is specifically categorized as an Add-ons & Tools subcategory. Echo is designed to monitor the messages passed across document iframes.

With Echo, users can easily track and analyze the messages exchanged between different iframes within a web document. This add-on provides a simple and efficient way to monitor the communication happening across multiple iframes, making it a valuable tool for developers and webmasters.

Echo's user-friendly interface allows users to configure and customize the monitoring settings according to their specific needs. It provides real-time updates and detailed logs of the message exchanges, enabling users to gain insights into the communication flow and troubleshoot any potential issues.

Overall, Echo is a useful Chrome add-on for monitoring messages across document iframes. It offers a convenient solution for developers and webmasters who need to keep track of the communication happening within their web applications.