Percent-encoding Reserved Characters
When a character from the reserved set (a "reserved character") has special meaning (a "reserved purpose") in a certain context, and a URI scheme says that it is necessary to use that character for some other purpose, then the character must be percent-encoded. Percent-encoding a reserved character involves converting the character to its corresponding byte value in ASCII and then representing that value as a pair of hexadecimal digits. The digits, preceded by a percent sign ("%") which is used as an escape character, are then used in the URI in place of the reserved character. (For a non-ASCII character, it is typically converted to its byte sequence in UTF-8, and then each byte value is represented as above.)
The reserved character "/", for example, if used in the "path" component of a URI, has the special meaning of being a delimiter between path segments. If, according to a given URI scheme, "/" needs to be in a path segment, then the three characters "%2F" or "%2f" must be used in the segment instead of a raw "/".
! |
# |
$ |
& |
' |
( |
) |
* |
+ |
, |
/ |
: |
; |
= |
? |
@ |
[ |
] |
%21 |
%23 |
%24 |
%26 |
%27 |
%28 |
%29 |
%2A |
%2B |
%2C |
%2F |
%3A |
%3B |
%3D |
%3F |
%40 |
%5B |
%5D |
Reserved characters that have no reserved purpose in a particular context may also be percent-encoded but are not semantically different from those that are not.
In the "query" component of a URI (the part after a ? character), for example, "/" is still considered a reserved character but it normally has no reserved purpose, unless a particular URI scheme says otherwise. The character does not need to be percent-encoded when it has no reserved purpose.
URIs that differ only by whether a reserved character is percent-encoded or appears literally are normally considered not equivalent (denoting the same resource) unless it can be determined that the reserved characters in question have no reserved purpose. This determination is dependent upon the rules established for reserved characters by individual URI schemes.
Read more about this topic: Percent-encoding, Percent-encoding in A URI
Famous quotes containing the words reserved and/or characters:
“Parents’ ability to survive a child’s unabating needs, wants, and demands...varies enormously. Some people can give and give....Whether children are good or bad, brilliant or just about normal, enormously popular or born loners, they keep their cool and say just the right thing at all times...even when they are miserable themselves, inexhaustible springs of emotional energy, reserved just for children, keep flowing unabated.”
—Stella Chess (20th century)
“White Pond and Walden are great crystals on the surface of the earth, Lakes of Light.... They are too pure to have a market value; they contain no muck. How much more beautiful than our lives, how much more transparent than our characters are they! We never learned meanness of them.”
—Henry David Thoreau (1817–1862)