> I can't imagine a valid use case for that outside of developers working against a local machine it's very useful to talk to locally installed applications wi

> I can't imagine a valid use case for that outside of developers working against a local machine it's very useful to talk to locally installed applications without having to write specific browser plugins for all browsers. Dropbox and Github are using it to detect the presence of their respective desktop apps. And I'm personally using it (with restrictive CORS header, referrer signature checking and only listening on localhost) to read a barcode scanner and put the data into a web application. We only had to write one app per OS we support instead of one app per OS and one extension per browser (which also means that this works in all HTML5 compatible browsers, not just those we deem worthy of our support).