Uniform Resource Locator

In computing, a Uniform Ability Locator or Universal Ability Locator (URL) is a specific appearance cord that constitutes a advertence to an Internet resource.

A URL is technically a blazon of Uniform Ability Identifier (URI) but in abounding abstruse abstracts and exact discussions URL is generally acclimated as a analogue for URI

History

The Uniform Resource Locator was created in 1994[2] by Tim Berners-Lee and the URI alive accumulation of the Internet Engineering Task Force (IETF) as an aftereffect of accord started at the IETF Living Documents "Birds of a Feather" affair in 1992. The architecture combines the above-mentioned arrangement of area names (created in 1985) with book aisle syntax, area advanced slashes are acclimated to abstracted binder and book names. Conventions already existed area server names could be prepended to complete book paths, preceded by a double-slash (//).

Syntax

Every URL consists of some of the following: the arrangement name (commonly alleged protocol), followed by a colon, two slashes,[note 1] then, depending on scheme, a area name[note 2] (alternatively, IP address), a anchorage number, the aisle of the ability to be fetched or the affairs to be run, then, for programs such as Common Gateway Interface (CGI) scripts, a concern string,[7][8] and an alternative fragment identifier.[9]

The syntax is

scheme://domain:port/path?query_string#fragment_id

The arrangement name defines the namespace, purpose, and the syntax of the actual allotment of the URL. Computer application will try to action a URL according to its arrangement and context. For example, a web browser will usually dereference the URL http://example.org:80 by assuming an HTTP appeal to the host at example.org, application anchorage cardinal 80. The URL mailto:bob@example.com may alpha an e-mail artisan with the abode bob@example.com in the To field.

Other examples of arrangement names accommodate https:, gopher:, wais:, ftp:. URLs with https as a arrangement (such as https://example.com/) crave that requests and responses will be fabricated over a defended affiliation to the website. Some schemes that crave affidavit acquiesce a username, and conceivably a countersign too, to be anchored in the URL, for archetype ftp://asmith@ftp.example.org. Passwords anchored in this way are not accessory to defended working, but the abounding accessible syntax is

scheme://username:password@domain:port/path?query_string#fragment_id

The area name or IP abode gives the destination area for the URL. The area google.com, or its IP abode 72.14.207.99, is the abode of Google's website.

The area name allocation of a URL is not case acute back DNS ignores case: http://en.example.org/ and HTTP://EN.EXAMPLE.ORG/ both accessible the aforementioned page.

The anchorage cardinal is optional; if omitted, the absence for the arrangement is used. For example, http://vnc.example.com:5800 connects to anchorage 5800 of vnc.example.com, which may be adapted for a VNC alien ascendancy session. If the anchorage cardinal is bare for an http: URL, the browser will affix on anchorage 80, the absence HTTP port. The absence anchorage for an https: appeal is 443.

The aisle is acclimated to specify and conceivably acquisition the ability requested. It is case-sensitive, admitting it may be advised as case-insensitive by some servers, abnormally those based on Microsoft Windows. If the server is case acute and http://en.example.org/wiki/URL is correct, http://en.example.org/WIKI/URL/ or http://en.example.org/wiki/url/ will affectation an HTTP 404 absurdity page, unless these URLs point to accurate assets themselves.

The concern cord contains abstracts to be anesthetized tocomputer application active on the server. It may accommodate name/value pairs afar by ampersands, for archetype ?first_name=John&last_name=Doe.

The fragment identifier, if present, specifies a allotment or a position aural the all-embracing ability or document. When acclimated with HTTP, it usually specifies a area or area aural the page, and the browser may annal to affectation that allotment of the pag

Absolute and relative URLs

According to RFC 1738, which authentic URLs in 1994, back assets accommodate references to added resources, they can use about links to ascertain the area of the additional ability as if to say, "in the aforementioned abode as this one except with the afterward about path". It went on to say that such about URLs are abased on the aboriginal URL absolute a hierarchical anatomy adjoin which the about articulation is based, and that the ftp, http, and book URL schemes are examples of some that can be advised hierarchical, with the apparatus of the bureaucracy actuality afar by "/"

URLs as locators

A URL is a URI that, "in accession to anecdotic a resource, provides a agency of analysis the ability by anecdotic its primary admission apparatus (e.g., its arrangement location)"

Internet hostnames

On the Internet, a hostname is a area name assigned to a host computer. This is usually a aggregate of the host's bounded name with its ancestor domain's name. For example, en.example.org consists of a bounded hostname (en) and the area name example.org. The hostname is translated into an IP abode via the bounded hosts file, or the Area Name Arrangement (DNS) resolver. It is accessible for a distinct host computer to accept several hostnames; but about the operating arrangement of the host prefers to accept one hostname that the host uses for itself.

Any area name can additionally be a hostname, as continued as the restrictions mentioned beneath are followed. For example, both "en.example.org" and "example.org" can be hostnames if they both accept IP addresses assigned to them. The area name "xyz.example.org" may not be a hostname if it does not accept an IP address, but "aa.xyz.example.org" may still be a hostname. All hostnames are area names, but not all area names are hostnames.