2.4.2. Parsing the Scheme

If the parse string contains a colon ":" after the first character and before any characters not allowed as part of a scheme name (i.e., any not an alphanumeric, plus "+", period ".", or hyphen "-"), the <scheme> of the URL is the substring of characters up to but not including the first colon. These characters and the colon are then removed from the parse string before continuing.