For other uses, see Wiki (disambiguation).

A wiki (pronounced , or ; see Pronunciation below) is a web application that allows users to add content, as on an Internet forum, but also allows anyone to edit the content. Wiki also refers to the collaborative software used to create such a website (see Wiki software).

Wiki (with an upper case 'W') and WikiWikiWeb are both used to refer specifically to the Portland Pattern Repository, the first wiki ever created. A lowercase 'w' for 'wiki' is generally used by savvy wiki proponents. The name was based on the Hawaiian term wiki wiki, meaning "quick" or "informal." It is used commonly in Hawaii as part of its rich "pidgin English"— the native language of the islands.

Sometimes wikiwiki or WikiWiki is used instead of wiki.



In most English-speaking countries wiki is usually pronounced or (IPA); in French, Polish, German, Greek, Hebrew, Hawaiian and Hawaiian English, it is sometimes pronounced or .

Key characteristics

A wiki enables documents to be written collectively (co-authoring) in a simple markup language using a web browser. A single page in a wiki is referred to as a "wiki page", while the entire body of pages, which are usually highly interconnected via hyperlinks, is called "the wiki"—in effect, a very simple relational database.

A defining characteristic of wiki technology is the ease with which pages can be created and updated. Generally, there is no review before modifications are accepted. Most wikis are open to the general public without the need to register any user account. Sometimes session log-in is requested to acquire a "wiki-signature" cookie for autosigning edits. More private wiki servers require user authentication.

Pages and editing

In a traditional wiki, there are three representations for each page:

  • The user-editable "source code," which is also the format stored locally on the server. It usually is plain text, made visible to the user only when the edit operation shows it in a browser form.
  • A template (possibly internally generated) that defines layout and elements common to all pages.
  • The rendered HTML code produced by the server on the fly from the source text when a particular page is requested.

The source format, sometimes known as "wikitext," is augmented with a simplified markup language to hint various structural and visual conventions. Perhaps the most widespread such convention is to use "*" to start a line of text desired to render as bullet-list items. Style and syntax can vary a great deal among implementations, some of which allow raw HTML tags as well.

The reasoning behind this design is that HTML with its many cryptic tags is not especially human-readable. Making typical HTML source visible makes the actual text content very hard to read and edit for most users. It is therefore better to promote plain-text editing with a few simple conventions for structure and style.

It is also sometimes viewed as beneficial that users cannot directly use all the functionality that HTML allows, such as JavaScript and Cascading Style Sheets. Consistency in look and feel is also achieved, along with some extra safety for the user. In many wiki implementations, an active hyperlink is exactly as it is shown, unlike in HTML where the invisible hyperlink can have an arbitrary visible anchor text.

Wiki syntax (MediaWiki) HTML Rendered output
"''Doctor''? No other title? A ''scholar''? And he rates above the civil authority?"

"Why, certainly," replied Hardin, amiably. "We're all scholars more or less. After all, we're not so much a world as a scientific foundation—under the direct control of the Emperor."


"<i>Doctor</i>? No other title? A <i>scholar</i>? And he rates above the civil authority?"
"Why, certainly," replied Hardin, amiably. "We're all scholars more or less. After all, we're not so much a world as a scientific foundation&mdash;under the direct control of the Emperor."

"Doctor? No other title? A scholar? And he rates above the civil authority?"

"Why, certainly," replied Hardin, amiably. "We're all scholars more or less. After all, we're not so much a world as a scientific foundation—under the direct control of the Emperor."

(Quotation above from Foundation by Isaac Asimov)

Some recent wiki engines use a different method: they provide "WYSIWYG" editing, usually by means of JavaScript or an ActiveX control that translates graphically entered formatting instructions such as "bold" and "italics" into the corresponding HTML tags. In these implementations, saving an edit amounts to submitting a new HTML version of the page to the server, although the user is shielded from this technical detail as the markup is generated transparently. Users who do not have the necessary plugin can typically still edit the page, usually by directly editing the raw HTML code.


While for years the de facto standard was the syntax of the original WikiWikiWeb, currently the formatting instructions vary considerably depending on the wiki engine. Simple wikis only allow basic text formatting, whereas more complex ones have support for tables, images, formulas, or even interactive elements such as polls and games. Many people switch between wiki engines. Because of the difficulty in using several syntaxes, many people are putting considerable effort into defining a wiki markup standard (see efforts by Meatball and TikiWiki (

Linking and creating pages

Wikis are a true hypertext medium, with non-linear navigational structures. Each page typically contains a large number of links to other pages. Hierarchical navigation pages often exist in larger wikis, often a consequence of the original page creation process, but they do not have to be used. Links are created using a specific syntax, the so-called "link pattern."

Originally, most wikis used CamelCase as a link pattern, produced by capitalizing words in a phrase and removing the spaces between them (the word "CamelCase" is itself an example of CamelCase). While CamelCase makes linking very easy, it also leads to links which are written in a form that deviates from the standard spelling. CamelCase-based wikis are instantly recognizable from the large number of links with names such as "TableOfContents" and "BeginnerQuestions". The term CamelCase comes from the uppercase "bumps" in the middle of the compound word, suggesting the humps of a camel. Note: It is easy for a wiki to render the visible anchor for such links "pretty" by reinserting spaces, and possibly also reverting to lower case.

CamelCase has many critics, and wiki developers looked for alternative solutions. The first to introduce so called "free links" using this _(free link format) was Cliki. Various wiki engines use single brackets, curly brackets, underscores, slashes or other characters as a link pattern.

Links across different wiki communities are possible using a special link pattern called InterWiki. Wikipedia allows links to pages which are below a given size to be highlighted, thereby making small pages, so-called "stubs", noticeable on all pages that link to them.

New pages in a wiki are usually created simply by creating the appropriate links on a topically related page. If the link does not exist, it is typically emphasized as a "broken" link. Following that link opens an edit window, which then allows the user to enter the text for the new page. This mechanism ensures that so-called "orphan" pages (which have no links pointing to them) are rarely created, and a generally high level of connectedness is retained.


Most wikis offer at least a title search, if not a full text search. The scalability of the search depends on whether the wiki engine uses a database or not; indexed database access is necessary for high speed searches on large wikis. On Wikipedia, the so-called "Go button" allows readers to directly view a page that matches the entered search criteria as closely as possible. The MetaWiki search engine was created to enable searches across multiple wikis.

Controlling changes

Missing image
History comparison reports highlight the changes between two revisions of a page.

Wikis generally practice the philosophy of making it easy to correct mistakes, rather than making it difficult to make them. Thus while wikis are very open, they provide a means to verify the validity of recent additions to the body of pages. The most prominent, on almost every wiki, is the "Recent Changes" page—a specific list numbering recent edits, or a list of all the edits made within a given timeframe. Some wikis can filter the list to remove minor edits and edits made by automatic importing scripts ("bots").

From the change log, two other functions are accessible in most wikis: the Revision History showing previous page versions; and the diff feature, highlighting the changes between two revisions. Using the Revision History, an editor can view and restore a previous version of the article. The diff feature can be used to decide whether or not this is necessary. A regular wiki user can view the diff of an edit listed on the "Recent Changes" page and, if it is an unacceptable edit, consult the history, restoring a previous revision; this process is more or less streamlined, depending on the wiki software used.

In case unacceptable edits are missed on the "Recent Changes" page, some wiki engines provide additional content control. It can be monitored to ensure that a page, or a set of pages, keeps its quality. A person willing to maintain pages will be warned of modifications to the pages, allowing him or her to quickly verify the validity of new editions.


The open philosophy of most wikis—of letting anyone edit content—does not ensure that editors are well-intentioned. Vandalism is a constant problem to wikis.

Spam attacks

Wikis have also been a frequent target of spammers, not because the spammer hopes to induce the wiki's readers into using his products or services, but because the interlinked nature of wikis can make outbound links appear to have high value to search engines (see page rank). A commonly used defense against spammers, delayed indexing of outbound links, allows a wiki's editors or participants to remove offending links quickly.

Suggestions to stop vandalism

There are many ways to stop vandalism. Many public wikis shun mandatory registration procedures; nevertheless, many major wiki engines (including MediaWiki, MoinMoin, UseModWiki and TWiki) provide ways to limit write access. Some wiki engines allow individual users to be banned as editors—accomplished by blocking their particular IP address or, if available, their usernames; however, many Internet service providers (ISPs) assign a new IP address for each login, so IP bans often can be circumvented relatively easily, and may prevent legitimate users from accessing features.

In addition, improperly configured web servers known as open proxies allow users with fixed IP addresses to circumvent IP bans. To deal with this problem, temporary IP bans are sometimes used—and extended to all IP addresses within a particular range—ensuring, thereby, that the vandal cannot edit pages within a given time; the underlying assumption is that this is often a sufficient deterrent. It may, however, still prevent some non-problematic users from the same ISP from using the service for the ban's duration.

It might reduce comment spam/vandalism when Wiki supports for the new link attribute "rel=nofollow". All major search engines will be watching for it; all publicly-accessible wikis should probably implement it in some way. See Preventing Comment Spam (, by Google for details.

As an emergency measure, some wikis allow the database to be switched to read-only mode, while others enforce a policy in which only established users—registered prior to an arbitrary cutoff date—can continue editing. Generally, any vandal's vandalism can be reverted, quickly and easily. More problematic, though, are subtle, undetected errors inserted to pages—for example, changing album release dates on discographies.

Many wikis allow pages to be protected from editing; in most wikis, this is used only in extreme and rare cases. Protected pages on Wikipedia, for example, can be edited only by the administrators, who can also revoke the protection (as well as induce it). Generally, such actions are considered as against the basic wiki philosophy, and are therefore usually avoided. At any given time, the English Wikipedia has perhaps twelve protected pages, out of hundreds of thousands.

Common defense against persistent vandals

A common defense against persistent vandals is simply to let them deface as many pages as they wish, knowing that they can easily be tracked and reverted after the vandal has left. This policy quickly becomes impractical however in the face of systematic or automated defacements born out of either anger or frustration.


Wiki software originated in the design pattern community as a way of writing and discussing pattern languages. The Portland Pattern Repository was the first wiki, established by Ward Cunningham on March 25, 1995. [1] ( He invented the wiki name and concept, and implemented the first wiki engine. Some people maintain that only the original wiki should be called Wiki (upper case) or the WikiWikiWeb.

Cunningham coined the term wiki after the "wiki wiki" or "quick" shuttle buses at Honolulu Airport. Wiki wiki was the first Hawaiian term he learned on his first visit to the islands, when the airport counter agent directed him to take the wiki wiki bus between terminals. According to Cunningham, "I chose wiki-wiki as an alliterative substitute for 'quick' and thereby avoided naming this stuff quick-web." [2] ( See also: List of computer term etymologies.

In the late 1990s, wikis increasingly were recognized as a promising way to develop private- and public-knowledge bases, and this potential inspired the founders of the Nupedia encyclopedia project, Jimbo Wales and Larry Sanger, to use wiki technology as a basis for an electronic encyclopedia: Wikipedia was launched in January 2001, it originally was based upon UseMod software, but later switched to its own, open source codebase, now adopted by many other wikis.

In 2005, the Los Angeles Times experimented with using a wiki in the editorial section of its web site. The project was quickly shuttered as vandals quickly defaced it and features to help distribute administration of the site had been disabled.

Today, the English-language Wikipedia is, by far, the world's largest wiki; the German-language Wikipedia is the second-largest, while the other Wikipedias fill many of the remaining slots. The fifth-largest wiki is, a Swedish-language knowledge base running UseMod software. The all-encompassing nature of Wikipedia is a significant factor in its growth, while many other wikis are highly specialized. Some also have attributed Wikipedia's rapid growth to its decision not to use CamelCase.

Wiki communities

All known public wikis are listed at WorldWideWiki: SwitchWiki (, which currently lists about 1000 public wiki communities (as of 2004-06-12).

The largest wikis are listed at List of largest wikis and Meatball: Biggest wikis (

One way of finding a wiki on a subject in which someone is interested is to follow the wiki-node network from wiki to wiki, or one could take a Wiki bus tour: TourBusStop.

For those interested in creating their own wiki, there are many publicly available "wiki farms," which can make both private, password-protected wikis and publicly-editable wikis. WikiCities, PeanutButterWiki, SeedWiki (, JotSpot ( and OddWiki ( are five such services; more at List of wiki farms.



See also


External links

ar:ويكي bg:Уики bm:Wiki ca:Wiki cs:Wiki da:WikiWiki de:Wiki et:Wiki es:Wiki eo:Vikio fa:ویکی‌ویکی fo:WikiWiki fr:Wiki ga:Vici gl:Wiki ko:위키위키 hr:Wiki id:Wiki ia:Wiki it:Wiki he:ויקי lv:Wiki lt:Wiki lb:Wiki li:Wiki hu:Wiki ms:Wiki zh-min-nan:Wiki nl:Wikiwiki ja:ウィキ nb:Wiki nn:Wiki pl:Wiki pt:Wiki ru:Вики simple:Wiki sk:Wiki sl:Wiki sr:Вики fi:Wiki sv:Wiki tl:Wiki tt:Wiki th:วิกิ vi:Wiki uk:Вікі zh:Wiki


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