Definition of whitespace in JSON

Question

JSON specifies that "Whitespace can be inserted between any pair of tokens." What it does not specify is exactly what whitespace is. Should I read this as "old-fashioned ASCII whitespace" or "the entire spectrum of Unicode whitespace"?

In other words, when parsing JSON, are U+2000, U+2001, U+FEFF etc. valid whitespace characters between tokens?

Answer 1

Insignificant whitespace is defined in the RFC4627 for JSON:

Insignificant whitespace is allowed before or after any of the six
structural characters.

  ws = *(
            %x20 /              ; Space
            %x09 /              ; Horizontal tab
            %x0A /              ; Line feed or New line
            %x0D                ; Carriage return
        )

By the way, the default encoding is UTF-8:

JSON text SHALL be encoded in Unicode. The default encoding is UTF-8.

That being said, I don't think they intended to accept all forms of Unicode spaces in the original implementation.