A hyperlink, commonly referred to as a link, is a text string (i.e., sequence of characters) or an image in an electronic document that serves as a user-activated switch that causes another, predetermined location in the same page or document or an entirely different page or document to appear on an electronic display screen in place of the original page or document. Links can also be used to initiate other activities, particularly the downloading of files from the Internet.
Hyperlinks are a fundamental component of the world wide web. But they are also used in other types of electronic documents, including PDF (portable document format) files and some word processing and spreadsheet files.
Text links can be any length, including a single letter, a word, a phrase, or an entire paragraph. They are usually indicated by a text color different from the surrounding text and/or by an underlining. The default color for an unvisited link is blue, and that for link that has recently been visited is purple; other colors can be selected by the web page designer as well as by the user by changing browser settings. Text links can also be designed so that other changes in the text occur while a mouse cursor passes (or hovers) over them, including in the color of the characters and their background color.
Both text and image links are indicated by a change in the shape of the mouse cursor when it passes over them. It typically changes from an inclined arrow (the default cursor shape) or an I-beam (the shape when it is over text) to a small image of a hand with one extended finger (perhaps representing the pushing of a switch with a single finger).
Hyperlinks are usually activated when a user places the mouse cursor over them and then clicks on a mouse button (by default the left button on a multi-button mouse). However, they can also be activated by keystrokes: first using the TAB key to select the link and then pressing the ENTER key.
To use slightly more technical terminology, each hyperlink has two ends, called anchors, and a direction. The link starts at the source anchor, usually just referred to as the link, and points to the destination anchor, also called the target. The most common target is a URL (universal resource locator), which can represent a web page (or other resource) or a location on a web page.
The term hyperlink was coined around 1965 by Theodor Nelson, an information technology pioneer. Nelson had been inspired by Vannevar Bush's classic 1945 article As We May Think1, which described a microfilm-based machine in which a user could link any two pages of information into a trail of related information and then scroll among them as if they were on a single microfilm reel.
Hypertext is text which contains one or more hyperlink. The origin of the word hyperlink might have been hypertext link.
Hypertext, inclusive of its hyperlinks, is revolutionizing how information is stored, accessed and created, and it is undoubtedly one of the greatest inventions of our time. However, it will likely be many years before the full implications of this invention are known and appreciated.
Created February 10, 2006.