Specs: https://html.spec.whatwg.org/#dom-navigator-registerprotocolhandler
Examples: https://developer.mozilla.org/zh-CN/docs/Web-based_protocol_handlers
Some answers: http://stackoverflow.com/questions/364895/register-an-application-to-a-url-protocol-all-browsers-via-installer http://stackoverflow.com/questions/7684663/external-protocol-handlers-and-modern-browsers