BroadcastChannel allows scripts from the same origin but other browsing contexts to send each other messages. Channels are scoped to an origin and have a name, messages posted to a channel will be delivered to all listeners of that channel in all documents.
Docs: https://developers.google.com/web/updates/2016/09/broadcastchannel https://developer.mozilla.org/en-US/docs/Web/API/Broadcast_Channel_API https://hacks.mozilla.org/2015/02/broadcastchannel-api-in-firefox-38/