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A Uniform Resource Locator, URL (spelled out as an acronym, not pronounced as 'earl'), or Web address, is a standardized address name layout for resources (such as documents or images) on the Internet (or elsewhere). First created by Tim Berners-Lee for use on the World Wide Web, the currently used forms are detailed by Internet standard RFC 1738. Sir Tim Berners-Lee Sir Tim (Timothy John) Berners-Lee, KBE (TimBL or TBL) (b. ...
Graphic representation of the World Wide Web around Wikipedia The World Wide Web (WWW, W3, or simply Web) is an information space in which the items of interest, referred to as resources, are identified by global identifiers called Uniform Resource Identifiers (URIs). ...
Internet standards are defined by the Internet Engineering Task Force (IETF). ...
The URL was a fundamental innovation in the history of the Internet. The syntax is designed to be generic, extensible, and able to express addresses in any character set using a limited subset of ASCII characters (for instance, whitespace is never used in a URL). URLs are classified by the "scheme" which typically identifies the network protocol used to retrieve the resource over a computer network. ...
There are 95 printable ASCII characters, numbered 32 to 126. ...
For information on the programming language Whitespace, see Whitespace programming language. ...
Definition
URIs and URLs Every URL is a type of Uniform Resource Identifier (URI), or more precisely the set of URLs is a proper subset of URIs. A URI identifies a particular resource while a URL both identifies a resource and indicates how to locate it. To illustrate the distinction consider the URI urn:ietf:rfc:1738 which identifies IETF RFC 1738 without indicating where to find the text of this RFC. Now consider three URLs for three separate documents containing the text of this RFC: A Uniform Resource Identifier (URI), is an Internet protocol element consisting of a short string of characters that conform to a certain syntax. ...
The Internet Engineering Task Force (IETF) is charged with developing and promoting Internet standards. ...
RFC may refer to Reconstruction Finance Corporation - Hoovers attempt to stem the Great Depression Royal Flying Corps - the over-land air arm of the British military during most of World War I Request For Change - ITIL terminology in the IT Service Management arena to describe a request to Change...
Each URL uniquely identifies each document and thus is a URI itself, but URL syntax is such that the identity allows one to also locate each of these documents. Thus, a URL functions as the document's address.
Historically, the terms have been almost synonymous as almost all URIs have also been URLs. For this reason, many definitions in this article mention URIs instead of URLs; the discussion applies to both URIs and URLs.
URL scheme A URL begins with the name of its scheme, followed by a colon, followed by a scheme-specific part.
Some examples of URL schemes:
See also http://www.iana.org/assignments/uri-schemes HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ...
Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. ...
The File Transfer Protocol (FTP) is a software standard for transferring computer files between machines with widely different operating systems. ...
Wikipedia does not yet have an article with this exact name. ...
The IETF designed and specified the Lightweight Directory Access Protocol, or LDAP, as a better way to make use of X.500 directories - having found the original Directory Access Protocol (DAP) too complex for simple internet clients to use. ...
A newsgroup is a repository, usually within the Usenet system, for messages posted from many users at different locations. ...
Gopher is a distributed document search and retrieval network protocol designed for the Internet. ...
Telnet is a network protocol used on the Internet or local area network LAN connections. ...
Generic URI syntax The syntax of the scheme-specific part depends on the requirements of the scheme. Schemes using typical connection-based protocols use a common "generic URI" syntax, defined below: scheme://authority/path?query The authority typically consists of a hostname or IP address of a server, optionally followed by a colon and a port number. It may in fact also contain information on username and password for authenticating to the server.
The path is a specification of a location in some hierarchical structure, using a slash ("/") as delimiter between components.
The query part is typically intended to express parameters of a dynamic query to some database residing on the server.
The complete, authoritative URI parameter/syntax is below:
scheme://username:password@subdomain.domain.tld:port/directory/file.ext?parameter=value#anchor
URI references The term URI reference means a particular instance of a URI as it is being used in, for instance an HTML document. It introduces two new concepts: the one of absolute and relative references, and that of a fragment identifier. In computing, HyperText Markup Language (HTML) is a hypertext markup language designed for the creation of web pages and other information viewable in a browser. ...
A fragment identifier is a short string of characters that refers to a resource that is subordinate to another, primary resource. ...
An absolute URL is just like a URL defined above. A relative URL comprises just the scheme-specific part, where the scheme is inferred from the context in which the URL reference appears (the Base URI).
A URI reference can also consist of a URI followed by a hash sign ("#") and a pointer to within the resource referenced by the URI as a whole. This is not a part of the URI as such, but is intended for the "user agent" (browser) to interpret after the resource has been retrieved. Therefore it is never sent to the server in HTTP GET requests.
examples:
http://www.wikipedia.org/w/wiki.phtml?title=Train&action=history http://www.wikipedia.org/wiki/Train#Model_railways
Case-sensitivity URLs in general are case-sensitive; however it is up to the server administrator to decide to respect case when responding to requests. For convenience some webservers send the same page for URLs differing only in case.
URLs in everyday use A HTTP URL combines into one simple address the four basic items of information necessary to retrieve a resource from anywhere on the Internet: - the protocol to use to communicate,
- the host (server) to communicate with,
- the network port on the server to connect to,
- the path to the resource on the server (for example, its file name).
A typical URL can look like: In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signalling, authentication, and error detection required to send information over a communications channel. ...
In computing, a server is: A computer software application that carries out some task (i. ...
In computing, a port (derived from seaport) (more the hole in the side of a ship to view to and from) is usually a connection through which data is sent and received. ...
A path is the general form of a file or directory name, giving a files name and its unique location in a file system. ...
http://en.wikipedia.org:80/wiki/Special:Search?search=train&go=Go where - http is the protocol,
- en.wikipedia.org is the host,
- 80 is the network port number on the server (as 80 is the default value for the HTTP protocol, this portion could have been omitted entirely),
- /encyclopedia/Special:Search is the resource path,
- ?search=train&go=Go is the query string; this part is optional.
Most web browsers do not require the user to enter "http://" to address a webpage, as HTTP is by far the most common protocol used in web browsers. Likewise, since 80 is the default port for http it is not usually specified. One usually just enters a partial URL such as www.wikipedia.org/wiki/Train. To go to a homepage one usually just enters the host name, such as www.wikipedia.org. In computing, a port (derived from seaport) is usually an interface through which data are sent and received. ...
HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ...
A query string is the part of a URL that conveys parametric data to the server. ...
A web browser is a software application that enables a user to display and interact with HTML documents hosted by web servers or held in a file system. ...
A webpage or web page is a page of the World Wide Web, usually in HTML/XHTML format (the file extensions are typically htm or html) and with hypertext links to enable navigation from one page or section to another. ...
Homepage or Home may refers to: the start page or main page of a website the page that is displayed when you enter only a domain name as URL (e. ...
Since the HTTP protocol allows a server to respond to a request by redirecting the web browser to a different URL, many servers additionally allow users to omit certain parts of the URL, such as the "www." part, or the trailing slash if the resource in question is a directory. However, these omissions technically make it a different URL, so the web browser cannot make these adjustments, and has to rely on the server to respond with a redirect. It is possible, but due to tradition rare, for a web server to serve two different pages for URLs that differ only in a trailing slash. This article is about the computing term. ...
Note that in en.wikipedia.org/wiki/Train, the hierarchical order of the five elements is org (generic top-level domain) - wikipedia (second-level domain) - en (subdomain) - wiki - Train; i.e. before the first slash from right to left, then the rest from left to right. A generic top-level domain (gTLD) is a top-level domain used (at least in theory) by a particular class of organization. ...
In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is part of a larger domain name. ...
The big picture The term URL is also used outside the context of the World Wide Web. Database servers specify URLs as a parameter to make connections to it. Similarly any Client-Server application following a particular protocol may specify a URL format as part of its communication process. A database is a collection of data elements (facts) stored in a computer in a systematic way, such that a computer program can consult it to answer questions. ...
Example of a database URL :
jdbc:datadirect:oracle://myserver:1521;sid=testdb If a webpage is uniquely and more or less permanently defined by a URL it can be linked to (see also permalink, deep linking). This is not always the case, e.g. a menu option may change the contents of a frame within the page, without this new combination having its own URL. A webpage may also depend on temporarily stored information. If the webpage or frame has its own URL, this is not always obvious for someone who wants to link to it: the URL of a frame is not shown in the address bar of the browser, and a page without address bar may have been produced. The URL may be derivable from the source code and/or "properties" of various components of the page. See also Webpage#URL. A hyperlink, or simply a link, is a reference in a hypertext document to another document or other resource. ...
A permalink (a portmanteau made by contracting the phrase permanent link) is a type of URL designed to refer to a specific information item (often a news story or weblog item) and to remain unchanged permanently, or at least for a lengthy period of time to prevent link rot. ...
Deep linking, on the World Wide Web, is the act of placing on a Web page a hyperlink that points to a specific page or image within another website, as opposed to that websites main or home page. ...
A webpage or web page is a page of the World Wide Web, usually in HTML/XHTML format (the file extensions are typically htm or html) and with hypertext links to enable navigation from one page or section to another. ...
Apart from the purpose of linking to a page or page component, one may want to know the URL to show the component alone, and/or to lift restrictions such as a browser window without toolbars, and/or of a small non-adjustable size.
Web servers also have the ability to redirect URLs if the destination has changed, allowing sites to change their structure without affecting existing links. This process is known as URL redirection. URL redirection is a technique on the world wide web for making a web page available under many URLs. ...
See also A Uniform Resource Identifier (URI), is an Internet protocol element consisting of a short string of characters that conform to a certain syntax. ...
Percent-encoding, also known as URL encoding, is a mechanism for encoding information in a Uniform Resource Identifier under certain circumstances. ...
The front page of the English Wikipedia website. ...
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