Every spelling of one destination that a URL parser might accept. Takes an address, a hostname or a whole URL — 127.0.0.1 , localhost , 169.254.169.254 , http://127.0.0.1:8080/admin — and returns the numeric forms ( 2130706433 , 0x7f000001 , 0177.0000.0000.0001 , 127.1 ), the other names for the same host, the separator tricks an IDNA parser folds away, and the userinfo and slash payloads that split a URL differently in two libraries. Port and path are carried into every payload.