WordNet (r) 3.0 (2006):

URL
    n 1: the address of a web page on the world wide web [syn:
         URL, uniform resource locator, universal resource
         locator]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

URL
       Uniform Resource Locator (WWW, RFC 1738)


The Jargon File (version 4.4.7, 29 Dec 2003):

URL
 /U?R?L/, /erl/, n.

    Uniform Resource Locator, an address widget that identifies a document or
    resource on the World Wide Web. This entry is here primarily to record the
    fact that the term is commonly pronounced both /erl/, and /U-R-L/ (the
    latter predominates in more formal contexts).


The Free On-line Dictionary of Computing (30 December 2018):

Uniform Resource Locator
Uniform Resource Locater
Universal Resource Locator
URL
web address

    (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 hypertext link which is often another HTML document
   (possibly stored on another computer).

   Here are some example URLs:

    http://w3.org/default.html
    http://acme.co.uk:8080/images/map.gif
    http://foldoc.org/?Uniform+Resource+Locator
    http://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 (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 "&;"
   character entity encodings (e.g. "é") are also accepted
   when URLs are embedded in HTML.  The terminating semicolon may
   be omitted if & is followed by a non-letter character.

   The authoritative W3C URL specification
   (http://w3.org/hypertext/WWW/Addressing/Addressing.html).

   (2000-02-17)