It isn't a URL. As per RFC 3986 [0]: > The term "Uniform Resource Locator" (URL) refers to the subset of URIs that [..] provide a means of locating the resourc

It isn't a URL. As per RFC 3986 [0]: > The term "Uniform Resource Locator" (URL) refers to the subset of URIs that [..] provide a means of locating the resource by describing its primary access mechanism Since "foo.bar" does not describe an access mechanism, it is not a URL. Yes, you could make the argument that "foo.bar" is a relative-path reference as described in section 4.2, but that is only used to: > express a URI reference relative to the name space of another hierarchical URI So "foo.bar" can only be considered a URL in the context of another given URL, and in your example there is none. [0] https://datatracker.ietf.org/doc/html/rfc3986#section-1.1.3 https://datatracker.ietf.org/doc/html/rfc3986#section-1.1.3