w3fools claims that URLs can contain spaces: http://w3fools.com/#html_urlencode
Is this true? How can a URL contain an un-encoded space?
I'm under the impression the request line of an HTTP Request uses a space as a delimiter, being formatted as {the method}{space}{the path}{space}{the protocol}:
GET /index.html http/1.1
Therefore how can a URL contain a space? If it can, where did the practice of replacing spaces with + come from?
Answer
A URL must not contain a literal space. It must either be encoded using the percent-encoding or a different encoding that uses URL-safe characters (like application/x-www-form-urlencoded that uses + instead of %20 for spaces).
But whether the statement is right or wrong depends on the interpretation: Syntactically, a URI must not contain a literal space and it must be encoded; semantically, a %20 is not a space (obviously) but it represents a space.