Date: 2020jul30 Q. Is a colon allowed in a URL (without being escaped)? A. Its not so simple. - Obviously, its NOT allowed in the scheme - Obviously, NOT allowed in username:password (if present) - It IS allowed in the path. eg https://en.wikipedia.org/wiki/Template:Welcome - It must be ESCAPED in the query - ie after the ? RFC2396 "Uniform Resource Identifiers (URI): Generic Syntax" says:

3.4. Query Component The query component is a string of information to be interpreted by the resource. query = *uric Within a query component, the characters ";", "/", "?", ":", "@", "&", "=", "+", ",", and "$" are reserved.

Encode colon as %3A in a query.