Universal Resource Locator ==>
Uniform Resource Locator
<World-Wide Web> (URL, previously "Universal") A standard way of
specifying the location of an object, typically a web page, on the Internet.
Other types of object are described below. URLs are the form of address used on
the World-Wide Web. They are used in HTML documents to specify the target of a
hyperlink which is often another HTML document (possibly stored on another
computer).
Here are some example URLs:
http://www.w3.org/default.html
http://www.acme.co.uk:8080/images/map.gif
http://foldoc.org/?Uniform+Resource+Locator
http://www.w3.org/default.html#Introduction
ftp://wuarchive.wustl.edu/mirrors/msdos/graphics/gifkit.zip
ftp://spy:secret@ftp.acme.com/pub/topsecret/weapon.tgz
mailto:fred@doc.ic.ac.uk
news:alt.hypertext
telnet://dra.com
The part before the first colon specifies the access scheme or protocol.
Commonly implemented schemes include: ftp, http
(World-Wide Web), gopher or WAIS. The "file" scheme
should only be used to refer to a file on the same
host. Other less commonly used schemes include news,
telnet or mailto (e-mail).
The part after the colon is interpreted according to the access scheme. In
general, two slashes after the colon introduce a hostname (host:port is also
valid, or for FTP user:passwd@host or user@host). The port number is usually
omitted and defaults to the standard port for the scheme, e.g. port 80 for HTTP.
For an HTTP or FTP URL the next part is a pathname which is usually related to
the pathname of a file on the server. The file can contain any type of data but
only certain types are interpreted directly by most browsers. These include HTML
and images in gif or jpeg format. The file's type is given by a MIME type in the
HTTP headers returned by the server, e.g. "text/html", "image/gif", and is
usually also indicated by its filename extension. A file whose type is not
recognised directly by the browser may be passed to an external "viewer"
application, e.g. a sound player.
The last (optional) part of the URL may be a query string preceded by "?" or a
"fragment identifier" preceded by "#". The later indicates a particular position
within the specified document.
Only alphanumerics, reserved characters (:/?#"<>%+) used for their reserved
purposes and "$", "-", "_", ".", "&", "+" are safe and may be transmitted
unencoded. Other characters are encoded as a "%" followed by two hexadecimal
digits. Space may also be encoded as "+". Standard SGML "&<name>;" character
entity encodings (e.g. "é") are also accepted when URLs are embedded in
HTML. The terminating semicolon may be omitted if &<name> is followed by a
non-letter character.
The authoritative W3C URL specification.
(2000-02-17)
Nearby terms:
Uniform Naming Convention « Uniform Resource
Citation « Uniform Resource Locater « Uniform
Resource Locator » Uniform Resource Name »
Uniform Resource Number » Unify
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