window.postMessage enables you to do cross-origin communication safely. This add-on has three server side components that enable your Vaadin application to do "Post Messaging" easily. Currently the only possible message type is String, but support for more types is planned. PostMessageReceiver - for receiving and responding to messages, ie. when your app is embedded in another application inside an iframe or is opened in a popup window. PostMessageIFrame - when you need to embed and communicate with another app. Extends BrowserFrame component from core Vaadin Framework. PostMessageWindowUtils - for opening a location in another browser window/tab and posting messages into them. NOTE: this is not supported by any IE version. Not possible currently to directly listen to messages from opened windows, but the PostMessageReceiver can be used for this.