|A full BNF description of the URL syntax is given in Section 5. |
In general, URLs are written as follows:
A URL contains the name of the scheme being used (<scheme>) followed
by a colon and then a string (the <scheme-specific-part>) whose
interpretation depends on the scheme.
Scheme names consist of a sequence of characters. The lower case
letters "a"--"z", digits, and the characters plus ("+"), period
("."), and hyphen ("-") are allowed.For resiliency, programs
interpreting URLs should treat upper case letters as equivalent to
lower case in scheme names (e.g., allow "HTTP" as well as "http").