Is there a character that is illegal in all parts of a URI?

Question

I need a character to separate two or more URIs in one string. Later I will the split the string to get each URI separately.

The problem is I'm not sure what character to pick here. Is there a good character to choose here that definitely can't be part of a URI itself? Or is ultimately pretty much all characters allowed in a URI?

I know certain characters are illegal in certain parts of the URI, but I'm talking about a URI as a whole, like this:

scheme://username:password@domain.tld/path/to/file.ext?key=value#blah

I'm thinking maybe space, although technically I suppose that could be part of the password, or would it be escaped as %20 in that case?

Answer 1

Any of the control characters should be good for this, such as TAB, FF and so on.

RFC3986 ^(a) controls the URI specification and Appendix A of that RFC states that the characters are limited to:

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
0123456789-._~:/?#[]@!$&'()*+,;=

(and the % encoding character, of course, for all other characters not listed above).

So, basically, any other character should be okay as a delimiter.

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^(a) This has actually been augmented by RFC6874 which has to do with changes to the IPv6 part of the URI, adding a zone identifier. Since the zone ID consists of % and "unreserved" characters already included above, it doesn't change the set of characters allowed.