URL

Short description: Web address to a particular file or page

URLUniform Resource Locator

Status| Published
First published| 1994; 32 years ago (1994)
Latest version| Living Standard
2023
Organization| Internet Engineering Task Force (IETF)
Committee| Web Hypertext Application Technology Working Group (WHATWG)
Editors| Anne van Kesteren
Authors| Tim Berners-Lee
Base standards|

* RFC 1738. – Uniform Resource Locators (URL).
* RFC 3986. – Uniform Resource Identifier (URI): Generic Syntax.
* RFC 4248. – The telnet URI Scheme.
* RFC 4266. – The gopher URI Scheme.
* RFC 6068. – The 'mailto' URI Scheme.
* RFC 6196. – Moving mailserver: URI Scheme to Historic.
* RFC 6270. – The 'tn3270' URI Scheme.

Related standards| URI, URN
Domain| World Wide Web
License| CC BY 4.0
Abbreviation| URL
Website| url.spec.whatwg.org

A Uniform Resource Locator (URL), colloquially known as an address on the Web,[1] is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI),[2][3] although many people use the two terms interchangeably.[4][lower-alpha 1] URLs occur most commonly to reference web pages (HTTP/HTTPS) but are 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. A typical URL could have the form `http://www.example.com/index.html`, which indicates a protocol (`http`), a hostname (`www.example.com`), and a file name (`index.html`).

## Contents

* 1 History
* 2 Syntax
* 3 Internationalized URL
* 4 Protocol-relative URLs
* 5 See also
* 6 Notes
* 7 Citations
* 8 References
* 9 External links

## History

Uniform Resource Locators were defined in RFC 1738 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),[7] as an outcome of collaboration started at the IETF Living Documents birds of a feather session in 1992.[7][8]

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 (`//`).[9]

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,[9] and also said that, given the colon following the first component of a URI, the two slashes before the domain name were unnecessary.[10]

Early WorldWideWeb collaborators including Berners-Lee originally proposed the use of UDIs: Universal Document Identifiers. An early (1993) draft of the HTML Specification[11] referred to "Universal" Resource Locators. This was dropped some time between June 1994 (RFC 1630) and October 1994 (draft-ietf-uri-url-08.txt).[12] 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.[13][14]

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.[15]

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/引き割り.html`. The target computer decodes the address and displays the page.[13]

## 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.[16][17]

## 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

## Notes

1. ↑ A URL implies the means to access an indicated resource and is denoted by a protocol or an access mechanism, which is not true of every URI.[5][4] Thus `http://www.example.com` is a URL, while `www.example.com` is not.[6]

## Citations

1. ↑ W3C (2009).
2. ↑ "Forward and Backslashes in URLs". https://zzz.buzz/2017/09/19/forward-and-backslashes-in-urls/.
3. ↑ RFC 3986 (2005).
4. ↑ 4.0 4.1 Joint W3C/IETF URI Planning Interest Group (2002).
5. ↑ RFC 2396 (1998).
6. ↑ "The Difference Between URLs and URIs". https://danielmiessler.com/study/url-uri/#gs.Hs64zOs.
7. ↑ 7.0 7.1 W3C (1994).
8. ↑ IETF (1992).
9. ↑ 9.0 9.1 Berners-Lee (2015).
10. ↑ BBC News (2009).
11. ↑ Berners-Lee, Tim; Connolly, Daniel "Dan" (March 1993). Hypertext Markup Language (draft RFCxxx) (Technical report). p. 28\. Archived from the original on 2017-10-23. Retrieved 2017-10-23.
12. ↑ Berners-Lee, Tim; Masinter, Larry; McCahill, Mark Perry (October 1994). Uniform Resource Locators (URL) (Technical report). (This Internet-Draft was published as a Proposed Standard RFC, RFC 1738 (1994)) Cited in Ang, C. S.; Martin, D. C. (January 1995). Constituent Component Interface++ (Technical report). UCSF Library and Center for Knowledge Management. Archived from the original on 2017-10-23. Retrieved 2017-10-23.
13. ↑ 13.0 13.1 W3C (2008).
14. ↑ W3C (2014).
15. ↑ IANA (2003).
16. ↑ (in en-US) Secure Development for Mobile Apps: How to Design and Code Secure Mobile Applications with PHP and JavaScript (1st ed.). CRC Press. March 10, 2014. p. 193. ISBN 978-1-48220903-7. https://books.google.com/books?id=6u2sBAAAQBAJ&pg=PA193. Retrieved 12 October 2015.
17. ↑ (in en-US) HTML, XHTML, and CSS Bible (1st ed.). John Wiley & Sons. 2011. p. 124. ISBN 978-1-11808130-3. https://books.google.com/books?id=DW0uyBZzEDwC&pg=PT124. Retrieved 12 October 2015.

## References

* "Berners-Lee "sorry" for slashes". BBC News. 14 October 2009. http://news.bbc.co.uk/1/hi/technology/8306631.stm.
* "Living Documents BoF Minutes". World Wide Web Consortium. 18 March 1992. http://www.w3.org/Conferences/IETF92/WWX_BOF_mins.html.
* Berners-Lee, Tim (21 March 1994). "Uniform Resource Locators (URL): A Syntax for the Expression of Access Information of Objects on the Network". World Wide Web Consortium. http://www.w3.org/Addressing/URL/url-spec.txt.
* Uniform Resource Locators (URL), December 1994, doi:10.17487/RFC1738, RFC 1738, https://tools.ietf.org/html/rfc1738, retrieved 31 August 2015
* "Why the //, #, etc?". Frequently asked questions. World Wide Web Consortium. 2015. http://www.w3.org/People/Berners-Lee/FAQ.html#etc.
* "Web addresses in HTML 5". World Wide Web Consortium. 21 May 2009. http://www.w3.org/html/wg/href/draft#url.
* IANA (14 February 2003). "Completion of IANA Selection of IDNA Prefix". IETF-Announce mailing list. http://www.atm.tut.fi/list-archive/ietf-announce/msg13572.html.
* Hypertext Markup Language – 2.0. Internet Engineering Task Force. November 1995. doi:10.17487/RFC1866. https://tools.ietf.org/html/rfc1866#section-8.2.1. Retrieved 13 September 2015.
* Uniform Resource Identifiers (URI): Generic Syntax, August 1998, doi:10.17487/RFC2396, RFC 2396, https://tools.ietf.org/html/rfc2396, retrieved 31 August 2015
* Thaler, Dave, ed. (June 2015), Guidelines and Registration Procedures for URI Schemes, doi:10.17487/RFC7595, RFC 7595, https://tools.ietf.org/html/rfc7595
* Report from the Joint W3C/IETF URI Planning Interest Group: Uniform Resource Identifiers (URIs), URLs, and Uniform Resource Names (URNs): Clarifications and Recommendations, August 2002, doi:10.17487/RFC3305, RFC 3305, https://tools.ietf.org/html/rfc3305, retrieved 13 September 2015
* Uniform Resource Identifiers (URI): Generic Syntax, January 2005, doi:10.17487/RFC3986, RFC 3986, https://tools.ietf.org/html/rfc3986, retrieved 31 August 2015
* Uniform Resource Identifiers (URI): Generic Syntax, section 3, Syntax Components, January 2005, doi:10.17487/RFC3986, RFC 3986, https://tools.ietf.org/html/rfc3986#section-3, retrieved 31 August 2015
* "An Introduction to Multilingual Web Addresses". 9 May 2008. http://www.w3.org/International/articles/idn-and-iri/.
* "What is Happening with "International URLs"". World Wide Web Consortium. 2014. https://www.w3.org/International/wiki/IRIStatus.
* Lawrence, Eric (2014-03-06). "Browser Arcana: IP Literals in URLs". https://docs.microsoft.com/en-us/archive/blogs/ieinternals/browser-arcana-ip-literals-in-urls.

## External links

* URL specification at WHATWG

* v
* t
* e

Hypermedia

Basics|

* Hypertext
* Hyperlink
* Hypertext fiction
* Hypervideo
* Adaptive hypermedia
* educational
* authoring
* Hyperlinks in virtual worlds

Resource identifiers|

* Uniform resource identifier
* Internationalized resource identifier
* Uniform resource name
* Uniform resource locator
* Extensible resource identifier
* Persistent uniform resource locator
* Semantic URL

Concepts|

* anchor text
* click path
* Domain name
* click here
* Copyright aspects of hyperlinking and framing
* deep linking
* Fat link
* Fragment identifier
* Hostname
* Hypertext
* Inline linking
* inbound link/backlink
* HTTP referer
* image map
* Internal link
* Internet bookmark
* linkback
* Link relation
* Link rot
* Object hyperlinking
* Path
* Screen hotspot
* Source tracking
* transclusion
* URI scheme
* URL normalization
* URL redirection
* Website
* Web page
* XML namespace

Technology|

* CURIE
* Hypertext Transfer Protocol
* XLink

See also|

* Digital poetry
* History of hypertext
* Interactive novel
* Interactive fiction
* Timeline of hypertext technology
* Copyright aspects of hyperlinking and framing
* World Wide Web
* Domain Application Protocol

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