URL

A uniform resource locator (URL), colloquially known as a web address, is a reference to a resource on the World Wide Web. A URL specifies the location of a resource on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI),Template:Ref RFC although many people use the two terms interchangeably.Template:Ref RFC A URL is most commonly used to reference a web page (HTTP/HTTPS) but is also used for file transfer (FTP), email (mailto), database access (JDBC), and many other applications.

Most web browsers display the URL of a web page above the page in an address bar. As an example of a web page URL, https://www.example.com/index.html indicates protocol https, hostname www.example.com, and file name index.html.

History

The Uniform Resource Locator was defined in Template:Sum RFC in 1994 by Tim Berners-Lee, the inventor of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at the IETF Living Documents birds of a feather session in 1992.

The format combines the pre-existing system of domain names (created in 1985) with file path syntax, where slashes are used to separate directory and filenames. Conventions already existed where server names could be prefixed to complete file paths, preceded by a double slash (//).

Berners-Lee later expressed regret at the use of dots to separate the parts of the domain name within URIs, wishing he had used slashes throughout, and also said that, given the colon following the first component of a URI, the two slashes before the domain name were unnecessary.

Early WorldWideWeb collaborators, including Berners-Lee, originally proposed the use of UDIs: Universal Document Identifiers. An early (1993) draft of the HTML Specification referred to "Universal" Resource Locators. This was dropped some time between June 1994Template:Ref RFC and October 1994. In his book Weaving the Web, Berners-Lee emphasizes his preference for the original inclusion of "universal" in the expansion rather than the word "uniform", to which it was later changed, and he gives a brief account of the contention that led to the change.

Syntax

Every HTTP URL conforms to the syntax of a generic URI. {{#section:Uniform resource identifier|syntax}}

A web browser will usually dereference a URL by performing an HTTP request to the specified host, by default on port number 80. URLs using the https scheme require that requests and responses be made over a secure connection to the website.

Internationalized URL

Internet users are distributed throughout the world using a wide variety of languages and alphabets, and expect to be able to create URLs in their own local alphabets. An Internationalized Resource Identifier (IRI) is a form of URL that includes Unicode characters. All modern browsers support IRIs. The parts of the URL requiring special treatment for different alphabets are the domain name and path.

The domain name in the IRI is known as an Internationalized Domain Name (IDN). Web and Internet software automatically convert the domain name into punycode usable by the Domain Name System; for example, the Chinese URL http://例子.卷筒纸 becomes http://xn--fsqu00a.xn--3lr804guic/. The xn-- indicates that the character was not originally ASCII.

The URL path name can also be specified by the user in the local writing system. If not already encoded, it is converted to UTF-8, and any characters not part of the basic URL character set are escaped as hexadecimal using percent-encoding; for example, the Japanese URL http://example.com/引き割り.html becomes http://example.com/%E5%BC%95%E3%81%8D%E5%89%B2%E3%82%8A.html. The target computer decodes the address and displays the page.

Protocol-relative URLs

Protocol-relative links (PRL), also known as protocol-relative URLs (PRURL), are URLs that have no protocol specified. For example, //example.com will use the protocol of the current page, typically HTTP or HTTPS.

See also

• Hyperlink
• PURL – Persistent URL
• CURIE (Compact URI)
• URI fragment
• Internet resource locator (IRL)
• Internationalized Resource Identifier (IRI)
• Clean URL
• Typosquatting
• Uniform Resource Identifier
• URI normalization
• Use of slashes in networking

References

• "Berners-Lee "sorry" for slashes". BBC News. 2009-10-14. Archived from the original on 2020-06-05. Retrieved 2010-02-14.
• "Living Documents BoF Minutes". World Wide Web Consortium. 1992-03-18. Archived from the original on 2012-11-22. Retrieved 2011-12-26.
• Berners-Lee, Tim (1994-03-21). "Uniform Resource Locators (URL): A Syntax for the Expression of Access Information of Objects on the Network". World Wide Web Consortium. Archived from the original on 2015-09-09. Retrieved 2015-09-13.
• Berners-Lee, Tim (2015) [2000]. "Why the //, #, etc?". Frequently asked questions. World Wide Web Consortium. Archived from the original on 2020-05-14. Retrieved 2010-02-03.
• Connolly, Daniel "Dan"; Sperberg-McQueen, C. Michael, eds. (2009-05-21). "Web addresses in HTML 5". World Wide Web Consortium. Archived from the original on 2015-07-10. Retrieved 2015-09-13.
• IANA (2003-02-14). "Completion of IANA Selection of IDNA Prefix". IETF-Announce mailing list. Archived from the original on 2004-12-08. Retrieved 2015-09-03.
• "An Introduction to Multilingual Web Addresses". 2008-05-09. Archived from the original on 2015-01-05. Retrieved 2015-01-11.
• Phillip, A. (2014). "What is Happening with "International URLs"". World Wide Web Consortium. Archived from the original on 2015-02-17. Retrieved 2015-01-11.
• Lawrence, Eric (2014-03-06). "Browser Arcana: IP Literals in URLs". Microsoft Learn. Archived from the original on 2020-06-22. Retrieved 2020-06-22.

External links

• URL specification at WHATWG
• URL splitter that splits any URI into its parts