URL

A Uniform Resource Locator, or URL (pronounces as "earl" (SAMPA: [@rl]) or spelled out), is a standardized address for some resource (such as a document or image) on the Internet. First created by Tim Berners-Lee for use on the World Wide Web, the currently used forms are detailed by IETF standard RFC 2396 (http://www.ietf.org/rfc/rfc2396.txt) (1998).

The URL was a fundamental innovation in creating the World Wide Web. It combines into one simple address the four basic items of information necessary to find a document anywhere on the Internet:

• The machine or domain name to go to
• An open network port on the target machine connected to some service
• The path or file name on that machine
• The protocol to use to communicate with that machine

A typical simple URL can look like:

   http://www.wikipedia.org:80/wiki

where

• http: specifies which protocol to use.
• //www.wikipedia.org specifies the domain name to contact.
• :80 specifies the network port number of the remote machine. Under most circumstances, this portion may be omitted entirely. In the case of the http protocol the default value is 80.
• /wiki is the request path on the specified system.

HTTP URLs can also contain additional elements, like a query string[?] (placed after the path and separated from it by a question mark (?)) containing information from a html form with method=get, or a name tag (placed after the path and separated from it by a sharp mark (#)) giving the location within a hypertext page to display.

see also URI, website, internet, History of the Internet