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In
computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, a hyperlink, or simply a link, is a digital reference to
data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interprete ...
that the user can follow or be guided by clicking or
tapping Tapping is a playing technique that can be used on any stringed instrument, but which is most commonly used on guitar. The technique involves a string being fretted and set into vibration as part of a single motion. This is in contrast to stand ...
. A hyperlink points to a whole document or to a specific element within a document.
Hypertext Hypertext is text displayed on a computer display or other electronic devices with references (hyperlinks) to other text that the reader can immediately access. Hypertext documents are interconnected by hyperlinks, which are typically ac ...
is text with hyperlinks. The text that is linked from is known as
anchor text The anchor text, link label or link text is the visible, clickable text in an HTML hyperlink. The term "anchor" was used in older versions of the HTML specification for what is currently referred to as the ''a element'', or . The HTML specific ...
. A software system that is used for viewing and creating hypertext is a ''hypertext system'', and to create a hyperlink is ''to hyperlink'' (or simply ''to link''). A user following hyperlinks is said to ''navigate'' or ''browse'' the hypertext. The document containing a hyperlink is known as its source document. For example, in an online reference work such as
Wikipedia Wikipedia is a Multilingualism, multilingual free online encyclopedia written and maintained by a community of online volunteering, volunteers, known as Wikipedians, through open collaboration and using a wiki-based editing system. Wikipedia ...
or
Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronic ...
, many words and terms in the text are hyperlinked to definitions of those terms. Hyperlinks are often used to implement reference mechanisms such as tables of contents,
footnotes A note is a string of text placed at the bottom of a page in a book or document or at the end of a chapter, volume, or the whole text. The note can provide an author's comments on the main text or citations of a reference work in support of th ...
,
bibliographies Bibliography (from and ), as a discipline, is traditionally the academic study of books as physical, cultural objects; in this sense, it is also known as bibliology (from ). English author and bibliographer John Carter describes ''bibliography ...
,
indexes Index (or its plural form indices) may refer to: Arts, entertainment, and media Fictional entities * Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index'' * The Index, an item on a Halo megastru ...
,
letters Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet), a character representing one or more of the sounds used in speech; any of the symbols of an alphabet. * Letterform, the graphic form of a letter of the alphabe ...
, and glossaries. In some hypertext, hyperlinks can be bidirectional: they can be followed in two directions, so both ends act as anchors and as targets. More complex arrangements exist, such as many-to-many links. The effect of following a hyperlink may vary with the hypertext system and may sometimes depend on the link itself; for instance, on the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ...
most hyperlinks cause the target document to replace the document being displayed, but some are marked to cause the target document to open in a new window (or, perhaps, in a new tab). Another possibility is
transclusion In computer science, transclusion is the inclusion of part or all of an electronic document into one or more other documents by reference via hypertext. Transclusion is usually performed when the referencing document is displayed, and is nor ...
, for which the link target is a document fragment that replaces the link anchor within the source document. Not only persons browsing the document may follow hyperlinks. These hyperlinks may also be followed automatically by programs. A program that traverses the hypertext, following each hyperlink and gathering all the retrieved documents is known as a Web ''spider'' or crawler.


Links


Inline links

An inline link displays remote content without the need for embedding the content. The remote content may be accessed with or without the user following the link. An inline link may display a modified version of the content; for instance, instead of an image, a
thumbnail Thumbnails are reduced-size versions of pictures or videos, used to help in recognizing and organizing them, serving the same role for images as a normal text index does for words. In the age of digital images, visual search engines and image- ...
,
low resolution Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be measured in various ways. Resolution quantifies how cl ...
preview, cropped section, or magnified section may be shown. The full content is then usually available on demand, as is the case with print publishing software e.g., with an
external link An internal link is a type of hyperlink on a web page to another page or resource, such as an image or document, on the same website or domain. Hyperlinks are considered either "external" or "internal" depending on their target or destinatio ...
. This allows for smaller file sizes and quicker response to changes when the full linked content is not needed, as is the case when rearranging a
page layout In graphic design, page layout is the arrangement of visual elements on a page. It generally involves organizational principles of composition to achieve specific communication objectives. The high-level page layout involves deciding on the ...
.


Anchor links

An anchor hyperlink (anchor link) is a link bound to a portion of a document, which is often called a fragment. The fragment is generally a portion of text or a heading, though not necessarily. For instance, it may also be a ''hot area'' in an image (
image map In HTML and XHTML, an image map is a list of coordinates relating to a specific image, created in order to hyperlink areas of the image to different destinations (as opposed to a normal image link, in which the entire area of the image links to a ...
in HTML), a designated, often irregular part of an image. Fragments are marked with ''anchors'' (in any of various ways), which is why a link to a fragment is called an anchor link (that is, a link to an anchor). For example, in XML, the element " provides anchoring capability (as long as the DTD or schema defines it), and in
wiki markup A wiki ( ) is an online hypertext publication Collaborative editing, collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be ...
, is a typical example of implementing it. In
word processor A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Word processor (electronic device), Early word processors were stand-alone devices ded ...
apps, anchors can be inserted where desired and may be called ''bookmarks''. In
URLs A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...
, the hash character (#) precedes the name of the anchor for the fragment. One way to define a hot area in an image is by a list of coordinates that indicate its boundaries. For example, a political map of Africa may have each country hyperlinked to further information about that country. A separate invisible hot area interface allows for swapping skins or labels within the linked hot areas without repetitive embedding of links in the various skin elements. Text hyperlink. Hyperlink is embedded into a word or a phrase and makes this text clickable. Image hyperlink. Hyperlink is embedded into an image and makes this image clickable. Bookmark hyperlink. Hyperlink is embedded into a text or an image and takes visitors to another part of a web page. E-mail hyperlink. Hyperlink is embedded into e-mail address and allows visitors to send an e-mail message to this e-mail address.


Fat links

A fat link (also known as a "one-to-many" link, an "extended link" or a "multi-tailed link") is a hyperlink which leads to multiple endpoints; the link is a
multivalued function In mathematics, a multivalued function, also called multifunction, many-valued function, set-valued function, is similar to a function, but may associate several values to each input. More precisely, a multivalued function from a domain to a ...
.


Uses in various technologies


HTML

Tim Berners-Lee Sir Timothy John Berners-Lee (born 8 June 1955), also known as TimBL, is an English computer scientist best known as the inventor of the World Wide Web. He is a Professorial Fellow of Computer Science at the University of Oxford and a profess ...
saw the possibility of using hyperlinks to link any information to any other information over the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...
. Hyperlinks were therefore integral to the creation of the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ...
. Web pages are written in the hypertext mark-up language
HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript ...
. This is what a hyperlink to the home page of the
W3C organization The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working to ...
could look like in HTML code: W3C organization website This HTML code consists of several tags: * The hyperlink starts with an anchor opening tag , and includes a hyperlink reference href="https://www.w3.org/" to the
URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifi ...
for the page. (Note that the URL is enclosed in quotes.) * The
URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifi ...
is followed by >, marking the end of the anchor opening tag. * The words that follow identify what is being linked; this is the only part of the code that is ordinarily visible on the screen when the page is rendered, but when the cursor hovers over the link, many browsers display the target URL somewhere on the screen, such as in the lower left-hand corner. * Typically these words are underlined and colored (for example, blue for a link that has not yet been visited and purple for a link already visited). * The anchor closing tag () terminates the hyperlink code. * The tag can also consist of various
attributes Attribute may refer to: * Attribute (philosophy), an extrinsic property of an object * Attribute (research), a characteristic of an object * Grammatical modifier, in natural languages * Attribute (computing), a specification that defines a proper ...
such as the "rel" attribute which specifies the relationship between the current document and linked document.
Webgraph The webgraph describes the directed links between pages of the World Wide Web. A graph, in general, consists of several vertices, some pairs connected by edges. In a directed graph, edges are directed lines or arcs. The webgraph is a directed graph ...
is a
graph Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties * Graph (topology), a topological space resembling a graph in the sense of discr ...
, formed from web pages as vertices and hyperlinks, as directed edges.


remove XLink: hyperlinks

The
W3C The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working t ...
recommendation called
XLink XML Linking Language, or XLink, is an XML markup language and W3C specification that provides methods for creating internal and external links within XML documents, and associating metadata with those links. The XLink specification XLink 1.1 is a ...
describes hyperlinks that offer a far greater degree of functionality than those offered in HTML. These extended links can be ''multidirectional'', remove linking from, within, and between XML documents. It can also describe ''simple links'', which are unidirectional and therefore offer no more functionality than hyperlinks in HTML.


Wikis

While
wiki A wiki ( ) is an online hypertext publication collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be either open to the pub ...
s may use HTML-type hyperlinks, the use of
wiki markup A wiki ( ) is an online hypertext publication Collaborative editing, collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be ...
, a set of
lightweight markup language A lightweight markup language (LML), also termed a simple or humane markup language, is a markup language with simple, unobtrusive syntax. It is designed to be easy to write using any generic text editor and easy to read in its raw form. Lightwei ...
s specifically for wikis, provides a simplified syntax for linking pages within wiki environments in other words, for creating wikilinks. The syntax and appearance of wikilinks may vary. Ward Cunningham's original
wiki software Wiki software (also known as a wiki engine or a wiki application), is collaborative software that runs a wiki, which allows the users to create and collaboratively edit pages or entries via a web browser. A wiki system is usually a web application ...
, the
WikiWikiWeb The WikiWikiWeb is the first wiki, or user-editable website. It was launched on 25 March 1995 by programmer Ward Cunningham to accompany the Portland Pattern Repository website discussing software design patterns. The name ''WikiWikiWeb'' ori ...
used
CamelCase Camel case (sometimes stylized as camelCase or CamelCase, also known as camel caps or more formally as medial capitals) is the practice of writing phrases without spaces or punctuation. The format indicates the separation of words with a single ...
for this purpose. CamelCase was also used in the early version of
Wikipedia Wikipedia is a Multilingualism, multilingual free online encyclopedia written and maintained by a community of online volunteering, volunteers, known as Wikipedians, through open collaboration and using a wiki-based editing system. Wikipedia ...
and is still used in some wikis, such as
TiddlyWiki TiddlyWiki is a personal wiki and a non-linear notebook for organising and sharing complex information. It is an open-source single page application wiki in the form of a single HTML file that includes CSS, JavaScript, embedded files such as i ...
,
Trac Trac is an open-source, web-based project management and bug tracking system. It has been adopted by a variety of organizations for use as a bug tracking system for both free and open-source software and proprietary projects and products. Tra ...
, and . A common markup syntax is the use of double square brackets around the term to be wikilinked. For example, the input "
zebras Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. ze ...
" is converted by wiki software using this markup syntax to a link to a
zebras Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. ze ...
article. Hyperlinks used in wikis are commonly classified as follows: * Internal wikilinks or intrawiki links lead to pages within the same wiki website. * Interwiki links are simplified markup hyperlinks that lead to pages of other wikis that are associated with the first. * External links lead to other webpages (those not covered in the above two cases, wiki or not wiki). Wikilinks are visibly distinct from other text, and if an internal wikilink leads to a page that does not yet exist, it usually has a different specific visual appearance. For example, in Wikipedia wikilinks are displayed in blue, except those that link to pages that don't yet exist, which are instead shown in
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...
. Another possibility for linking is to display a highlighted clickable question mark after the wikilinked term.


Virtual worlds

Hyperlinks are being implemented in various 3D
virtual world A virtual world (also called a virtual space) is a computer-simulated environment which may be populated by many users who can create a personal avatar, and simultaneously and independently explore the virtual world, participate in its activities ...
networks, including those that use the OpenSimulator and
Open Cobalt Open Cobalt is a free and open-source software platform for constructing, accessing, and sharing virtual worlds both on local area networks or across the Internet, with no need for centralized servers. The technology makes it easy to create dee ...
platforms.


Permalinks

Permalink A permalink or permanent link is a URL that is intended to remain unchanged for many years into the future, yielding a hyperlink that is less susceptible to link rot. Permalinks are often rendered simply, that is, as clean URLs, to be easier to ...
s are URLs that are intended to remain unchanged for many years into the future, yielding hyperlinks that are less susceptible to link rot. Permalinks are often rendered simply, that is, as friendly URLs, so as to be easy for people to type and remember. Permalinks are used in order to point and
redirect Redirect and its variants (e.g., redirection) may refer to: Arts, entertainment, and media * ''Redirect'', 2012 Christian metal album and its title track by Your Memorial * ''Redirected'' (film), a 2014 action comedy film Computing * ICMP Re ...
readers to the same Web page, blog post or any online digital media. The scientific literature is a place where link persistence is crucial to the public knowledge. A 2013 study in
BMC Bioinformatics ''BMC Bioinformatics'' is a peer-reviewed open access scientific journal covering bioinformatics and computational biology published by BioMed Central. It was established in 2000, and has been one of the fastest growing and most successful journal ...
analyzed 15,000 links in abstracts from Thomson Reuters’ Web of Science citation index, founding that the median lifespan of Web pages was 9.3 years, and just 62% were archived. The median lifespan of a Web page constitutes high-degree variable, but its
order of magnitude An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic d ...
usually is of some months.


How hyperlinks work in HTML

A link from one domain to another is said to be ''outbound'' from its source anchor and ''inbound'' to its target. The most common destination anchor is a
URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifi ...
used in the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ...
. This can refer to a document, e.g. a webpage, or other resource, or to a position in a webpage. The latter is achieved by means of an
HTML element An HTML element is a type of HTML (HyperText Markup Language) document component, one of several types of HTML nodes (there are also text nodes, comment nodes and others). The first used version of HTML was written by Tim Berners-Lee in 1993 ...
with a "name" or "id" attribute at that position of the HTML document. The URL of the position is the URL of the webpage with a
fragment identifier In computer hypertext, a URI fragment is a string of characters that refers to a resource that is subordinate to another, primary resource. The primary resource is identified by a Uniform Resource Identifier (URI), and the fragment identifier ...
"#''id attribute''" appended. When linking to PDF documents from an HTML page the "''id attribute''" can be replaced with syntax that references a page number or another element of the PDF, for example, "#''page=386''".


Link behavior in web browsers

A
web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used ...
usually displays a hyperlink in some distinguishing way, e.g. in a different
color Color ( American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are ass ...
,
font In metal typesetting, a font is a particular size, weight and style of a typeface. Each font is a matched set of type, with a piece (a "sort") for each glyph. A typeface consists of a range of such fonts that shared an overall design. In mod ...
or
style Style is a manner of doing or presenting things and may refer to: * Architectural style, the features that make a building or structure historically identifiable * Design, the process of creating something * Fashion, a prevailing mode of clothing ...
, or with certain symbols following to visualize link target or document types. This is also called ''link decoration''. The behavior and style of links can be specified using the
Cascading Style Sheets Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS is a cornerstone techno ...
(CSS) language. In a graphical user interface, the appearance of a
mouse A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus'' ...
cursor Cursor may refer to: * Cursor (user interface), an indicator used to show the current position for user interaction on a computer monitor or other display device * Cursor (databases), a control structure that enables traversal over the records in ...
may change into a
hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each " ...
motif to indicate a link. In most graphical web browsers, links are displayed in underlined blue text when they have not been visited, but underlined purple text when they have. When the user activates the link (e.g., by clicking on it with the mouse) the browser displays the link's target. If the target is not an HTML file, depending on the
file type A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file formats ...
and on the browser and its plugins, another program may be activated to open the file. The HTML code contains some or all of the five main characteristics of a link: * link destination ("href" pointing to a URL) *
link label The anchor text, link label or link text is the visible, clickable text in an HTML hyperlink. The term "anchor" was used in older versions of the HTML specification for what is currently referred to as the ''a element'', or . The HTML specifica ...
* link title * link target * link class or link id It uses the HTML element "a" with the attribute "href" (HREF is an abbreviation for "Hypertext REFerence") and optionally also the attributes "title", "target", and " class" or "id": :<a href="''URL''" title="''link title''" target="''link target''" class="''link class''">''link label''</a> To embed a link into a web page, blogpost, or comment, it may take this form: :Example In a typical web browser, this would display as the underlined word "Example" in blue, which when clicked would take the user to the example.com website. This contributes to a clean, easy to read text or document. By default, browsers will usually display hyperlinks as such: * An unvisited link is usually blue and underlined * A visited link is usually purple and underlined * An active link is usually red and underlined When the cursor hovers over a link, depending on the browser and graphical user interface, some informative text about the link can be shown, popping up, not in a regular
window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mater ...
, but in a special hover box, which disappears when the cursor is moved away (sometimes it disappears anyway after a few seconds, and reappears when the cursor is moved away and back).
Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current an ...
, IE,
Opera Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libre ...
, and many other web browsers all show the URL. In addition, the URL is commonly shown in the
status bar A status bar is a graphical control element which poses an information area typically found at the window's bottom. It can be divided into sections to group information. Its job is primarily to display information about the current state of its ...
. Normally, a link opens in the current
frame A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (co ...
or window, but sites that use frames and multiple windows for navigation can add a special "target" attribute to specify where the link loads. If no window exists with that name, a new window is created with the ID, which can be used to refer to the window later in the browsing session. Creation of new windows is probably the most common use of the "target" attribute. To prevent accidental reuse of a window, the special window names "_blank" and "_new" are usually available, and always cause a new window to be created. It is especially common to see this type of link when one large website links to an external page. The intention in that case is to ensure that the person browsing is aware that there is no endorsement of the site being linked to by the site that was linked from. However, the attribute is sometimes overused and can sometimes cause many windows to be created even while browsing a single site. Another special page name is "_top", which causes any frames in the current window to be cleared away so that browsing can continue in the full window.


History

The term "link" was coined in 1965 (or possibly 1964) by
Ted Nelson Theodor Holm Nelson (born June 17, 1937) is an American pioneer of information technology, philosopher, and sociologist. He coined the terms ''hypertext'' and ''hypermedia'' in 1963 and published them in 1965. Nelson coined the terms ''transcl ...
at the start of
Project Xanadu Project Xanadu ( ) was the first hypertext project, founded in 1960 by Ted Nelson. Administrators of Project Xanadu have declared it superior to the World Wide Web, with the mission statement: "Today's popular software simulates paper. The World ...
. Nelson had been inspired by "
As We May Think "As We May Think" is a 1945 essay by Vannevar Bush which has been described as visionary and influential, anticipating many aspects of information society. It was first published in '' The Atlantic'' in July 1945 and republished in an abridged ...
", a popular 1945 essay by
Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almost all wartim ...
. In the essay, Bush described a microfilm-based machine (the
Memex Memex is a hypothetical electromechanical device for interacting with microform documents and described in Vannevar Bush's 1945 article "As We May Think". Bush envisioned the memex as a device in which individuals would compress and store all of ...
) in which one could link any two pages of information into a "trail" of related information, and then scroll back and forth among pages in a trail as if they were on a single microfilm reel. In a series of books and articles published from 1964 through 1980, Nelson transposed Bush's concept of automated cross-referencing into the computer context, made it applicable to specific text strings rather than whole pages, generalized it from a local desk-sized machine to a theoretical proprietary worldwide computer network, and advocated the creation of such a network. Though Nelson's Xanadu Corporation was eventually funded by
Autodesk Autodesk, Inc. is an American multinational software corporation that makes software products and services for the architecture, engineering, construction, manufacturing, media, education, and entertainment industries. Autodesk is headquartered ...
in the 1980s, it never created this proprietary public-access network. Meanwhile, working independently, a team led by
Douglas Engelbart Douglas Carl Engelbart (January 30, 1925 – July 2, 2013) was an American engineer and inventor, and an early computer and Internet pioneer. He is best known for his work on founding the field of human–computer interaction, particularly ...
(with Jeff Rulifson as chief
programmer A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software. A programmer is someone who writes/creates ...
) was the first to implement the hyperlink concept for scrolling within a single document (1966), and soon after for connecting between paragraphs within separate documents (1968), with NLS.
Ben Shneiderman Ben Shneiderman (born August 21, 1947) is an American computer scientist, a Distinguished University Professor in the University of Maryland Department of Computer Science, which is part of the University of Maryland College of Computer, Mathem ...
working with graduate student Dan Ostroff designed and implemented the highlighted link in th
HyperTIES system
in 1983. HyperTIES was used to produce the world's first electronic journal, the July 1988 Communications of ACM, which was cited as the source for the link concept in
Tim Berners-Lee Sir Timothy John Berners-Lee (born 8 June 1955), also known as TimBL, is an English computer scientist best known as the inventor of the World Wide Web. He is a Professorial Fellow of Computer Science at the University of Oxford and a profess ...
's Spring 1989 manifesto for the Web. In 1988,
Ben Shneiderman Ben Shneiderman (born August 21, 1947) is an American computer scientist, a Distinguished University Professor in the University of Maryland Department of Computer Science, which is part of the University of Maryland College of Computer, Mathem ...
and Greg Kearsley used HyperTIES to publish "Hypertext Hands-On!", the world's first electronic book. Released in 1987 for the Apple Macintosh, the database program
HyperCard HyperCard is a software application and development kit for Apple Macintosh and Apple IIGS computers. It is among the first successful hypermedia systems predating the World Wide Web. HyperCard combines a flat-file database with a graphical, fle ...
allowed for hyperlinking between various pages within a document, as well as to other documents and separate applications on the same computer. In 1990,
Windows Help Microsoft WinHelp is a proprietary format for online help files that can be displayed by the Microsoft Help browser ''winhelp.exe'' or ''winhlp32.exe''. The file format is based on Rich Text Format (RTF). It remained a popular Help platform from ...
, which was introduced with
Microsoft Windows 3.0 Windows 3.0 is the third major release of Microsoft Windows, launched in 1990. It features a new graphical user interface (GUI) where applications are represented as clickable icons, as opposed to the list of file names seen in its predecess ...
, had widespread use of hyperlinks to link different pages in a single help file together; in addition, it had a visually different kind of hyperlink that caused a popup help message to appear when clicked, usually to give definitions of terms introduced on the help page. The first widely used open protocol that included hyperlinks from any Internet site to any other Internet site was the Gopher protocol from 1991. It was soon eclipsed by HTML after the 1993 release of the
Mosaic browser NCSA Mosaic is a discontinued web browser, one of the first to be widely available. It was instrumental in popularizing the World Wide Web and the general Internet by integrating multimedia such as text and graphics. It was named for its support ...
(which could handle Gopher links as well as HTML links). HTML's advantage was the ability to mix graphics, text, and hyperlinks, unlike Gopher, which just had menu-structured text and hyperlinks.


Legal issues

While hyperlinking among webpages is an intrinsic feature of the web, some websites object to being linked by other websites; some have claimed that linking to them is not allowed without permission. Contentious in particular are deep links, which do not point to a site's
home page A home page (or homepage) is the main web page of a website. The term may also refer to the start page shown in a web browser when the application first opens. Usually, the home page is located at the root of the website's domain or subdomain ...
or other entry point designated by the site owner, but to content elsewhere, allowing the user to bypass the site's own designated flow, and ''inline links'', which incorporate the content in question into the pages of the linking site, making it seem part of the linking site's own content unless an explicit attribution is added. In certain
jurisdiction Jurisdiction (from Latin 'law' + 'declaration') is the legal term for the legal authority granted to a legal entity to enact justice. In federations like the United States, areas of jurisdiction apply to local, state, and federal levels. Ju ...
s, it is or has been held that hyperlinks are not merely
reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a '' name'' ...
s or
citations A citation is a reference to a source. More precisely, a citation is an abbreviated alphanumeric expression embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose o ...
, but are devices for copying web pages. In the Netherlands,
Karin Spaink Karin Spaink (born December 20, 1957 in Amsterdam) is a journalist, writer and feminist. Spaink is a free speech advocate and social critic. Some of her subjects are: * New-age writers who assert all diseases are only a psychological phenomeno ...
was initially convicted in this way of copyright infringement by linking, although this ruling was overturned in 2003. The courts that advocate this view see the mere
publication To publish is to make content available to the general public.Berne Con ...
of a hyperlink that connects to illegal material to be an illegal act in itself, regardless of whether referencing illegal material is illegal. In 2004,
Josephine Ho Josephine Chuen-juei Ho, is the chair of the English department of National Central University, Taiwan, and coordinator of itCenter For the Study of Sexualities She has withstood lawsuits directed at her outspokenness on gender and rights issues ...
was acquitted of 'hyperlinks that corrupt traditional values' in
Taiwan Taiwan, officially the Republic of China (ROC), is a Country, country in East Asia, at the junction of the East China Sea, East and South China Seas in the northwestern Pacific Ocean, with the China, People's Republic of China (PRC) to the n ...
. In 2000,
British Telecom BT Group plc ( trading as BT and formerly British Telecom) is a British multinational telecommunications holding company headquartered in London, England. It has operations in around 180 countries and is the largest provider of fixed-line, bro ...
sued Prodigy, claiming that Prodigy infringed its patent () on web hyperlinks. After
litigation - A lawsuit is a proceeding by a party or parties against another in the civil court of law. The archaic term "suit in law" is found in only a small number of laws still in effect today. The term "lawsuit" is used in reference to a civil act ...
, a
court A court is any person or institution, often as a government institution, with the authority to adjudicate legal disputes between parties and carry out the administration of justice in civil, criminal, and administrative matters in accord ...
found for Prodigy, ruling that
British Telecom BT Group plc ( trading as BT and formerly British Telecom) is a British multinational telecommunications holding company headquartered in London, England. It has operations in around 180 countries and is the largest provider of fixed-line, bro ...
's patent did not cover web hyperlinks. In
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
''
jurisprudence Jurisprudence, or legal theory, is the theoretical study of the propriety of law. Scholars of jurisprudence seek to explain the nature of law in its most general form and they also seek to achieve a deeper understanding of legal reasoning ...
'', there is a distinction between the mere act of linking to someone else's website, and linking to content that is illegal (e.g., gambling illegal in the US) or infringing (e.g., illegal MP3 copies). Several courts have found that merely linking to someone else's website, even if by bypassing commercial advertising, is not copyright or trademark infringement, regardless of how much someone else might object. Linking to illegal or infringing content can be sufficiently problematic to give rise to legal liability. Compare for a summary of the current status of US copyright law as to hyperlinking, see the discussion regarding the ''Arriba Soft'' and ''Perfect 10'' cases. Somewhat controversially,
Vuestar Technologies Vuestar Technologies Pte Ltd is a Singapore-incorporated subsidiary owned by Australian parent Goldspirit Investments Pty Ltd. The owner of both companies, Ronald Neville Langford, applied for a number of patents around the world relating to search ...
has tried to enforce
patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
s applied for by its owner, Ronald Neville Langford,TelecomTV – TelecomTV One – News
around the world relating to search techniques using hyperlinked images to other
websites A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google, Facebook, Amazon, and Wikipe ...
or web pages.All your Interwibble is belong to us
Silvie Barak,
The Inquirer ''The Inquirer'' (stylized as TheINQUIRER) was a British technology tabloid website founded by Mike Magee after his departure from ''The Register'' (of which he was one of the founding members) in 2001. In 2006 the site was acquired by Dutch ...
, 21 February 2009


See also

*
Backlink A backlink is a link from some other website (the referrer) to that web resource (the referent). A ''web resource'' may be (for example) a website, web page, or web directory. A backlink is a reference comparable to a citation. The quantity, ...
*
Dereference In computer programming, the dereference operator or indirection operator, sometimes denoted by "*" (i.e. an asterisk), is a unary operator (i.e. one with a single operand) found in C-like languages that include pointer variables. It operates ...
(operator) *
Internal link An internal link is a type of hyperlink on a web page to another page or resource, such as an image or document, on the same website or domain. Hyperlinks are considered either "external" or "internal" depending on their target or destination. ...
* Link building *
Link rot Link rot (also called link death, link breaking, or reference rot) is the phenomenon of hyperlinks tending over time to cease to point to their originally targeted file, web page, or server due to that resource being relocated to a new address ...
*
Object hyperlinking Object hyperlinking is a term that refers to extending the Internet to objects and locations in the real world. Object hyperlinking aims to extend the Internet to the physical world by attaching tags with URLs to tangible objects or locations. These ...
*
PageRank PageRank (PR) is an algorithm used by Google Search to rank web pages in their search engine results. It is named after both the term "web page" and co-founder Larry Page. PageRank is a way of measuring the importance of website pages. According ...
*
URI fragment In computer hypertext, a URI fragment is a string of characters that refers to a resource that is subordinate to another, primary resource. The primary resource is identified by a Uniform Resource Identifier (URI), and the fragment identifier po ...
*
Xenu's Link Sleuth Xenu, or Xenu's Link Sleuth, is a computer program that checks websites for broken hyperlinks. It is written by Tilman Hausherr and is proprietary software available at no charge. The program is named after Xenu, the Galactic Ruler from Scien ...
*
Nofollow nofollow is a setting on a web page hyperlink that directs search engines not to use the link for page ranking calculations. It is specified in the page as a type of link relation; that is: <a rel="nofollow" ...>. Because search engines o ...


References


Further reading

* {{Authority control Graphical control elements Hypertext