Is URL percent-encoding case sensitive?

Question

Is %3B treated differently to %3b in an URL?

Answer 1

No, URL percent-encoding is NOT case sensitive. According to RFC 3986:

2.1. Percent-Encoding

[...]

The uppercase hexadecimal digits 'A' through 'F' are equivalent to the lowercase digits 'a' through 'f', respectively. If two URIs differ only in the case of hexadecimal digits used in percent-encoded octets, they are equivalent.