Wikipedia (IPA: [/ˌwɪkiˈpiːdi.ə/] or [/ˌwiki-/]) is a multilingual Web-based free-content encyclopedia.

It exists as a wiki, and is written collaboratively by volunteers, allowing most articles to be changed by anyone with access to a web browser and an Internet connection. The project began on January 15, 2001, as a complement to the expert-written (and now defunct) Nupedia, and is now operated by the non-profit Wikimedia Foundation. Wikipedia has more than 3,700,000 articles in many languages, including more than 1,000,000 in the English-language version. Since its inception, Wikipedia has steadily risen in popularity,[1] and has spawned several sister projects. Editors are required to uphold a policy of "neutral point of view" under which notable perspectives are summarized without an attempt to determine an objective truth.

Wikipedia’s co-founder Jimmy Wales has called it "an effort to create and distribute a multilingual free encyclopedia of the highest possible quality to every single person on the planet in their own language."[2] However, there has been controversy over its reliability and accuracy. Common points of criticism are vandalism, inconsistency, uneven quality, unsubstantiated opinions, systemic bias, and preference of consensus or popularity to credentials. In addition, some critics have suggested that Wikipedia cannot justifiably be called an "encyclopedia", a term which (it is claimed) implies a high degree of reliability and authority that Wikipedia, due to its open editorial policies, may not be able to maintain. Nevertheless, its free distribution, constant updates, diverse and detailed coverage, and its numerous multilingual versions have made it a much-used reference source for many. The word "Wikipedia" is a portmanteau of wiki and encyclopedia.

There are over 200 language editions of Wikipedia, around 100 of which are active. Fourteen editions have more than 50,000 articles each: English, German, French, Polish, Japanese, Dutch, Italian, Swedish, Portuguese, Spanish, Russian, Chinese, Norwegian, and Finnish. Its German-language edition has been distributed on DVD-ROM, and there are also proposals for an English DVD/paper edition. Many of its other editions are mirrored or have been forked by other websites.

Wikipedia’s slogan is "The free encyclopedia that anyone can edit." It is developed using a type of software called a "wiki", a term originally used for the WikiWikiWeb and derived from the Hawaiian wiki wiki, which means "quick." Jimmy Wales intends for Wikipedia to achieve a "Britannica or better" quality and be published in print. Although several other encyclopedia projects exist or have existed on the Internet, none has achieved Wikipedia’s size and popularity. Traditional multilingual editorial policies and article ownership are used in some, such as the expert-written Stanford Encyclopedia of Philosophy and the now-defunct Nupedia. More casual websites such as h2g2 or Everything2 serve as general guides, the articles of which are written and controlled by individuals. Projects such as Wikipedia,, Enciclopedia Libre and WikiZnanie are wikis in which articles are developed by numerous authors, and there is no formal process of review. Wikipedia has become the largest such encyclopedic wiki by article and word count. Unlike many encyclopedias, it has licensed its content under the GNU Free Documentation License.

Wikipedia has a set of policies identifying types of information appropriate for inclusion. These policies are often cited in disputes over whether particular content should be added, revised, transferred to a sister project, or removed.

Free content

The GNU Free Documentation License (GFDL), the license through which Wikipedia’s articles are made available, is one of many "copyleft" copyright licenses that permit the redistribution, creation of derivative works, and commercial use of content provided its authors are attributed and this content remains available under the GFDL. When an author contributes original material to the project, the copyright over it is retained with them, but they agree to make the work available under the GFDL. Material on Wikipedia may thus be distributed multilingually to, or incorporated from, resources which also use this license. Wikipedia’s content has been mirrored or forked by hundreds of resources from database dumps. Although all text is available under the GFDL, a significant percentage of Wikipedia’s images and sounds are non-free. Items such as corporate logos, song samples, or copyrighted news photos are used with a claim of fair use. [3] Less frequently, it has been used in academic studies, books, conferences, and court cases. For instance, the Parliament of Canada website refers to Wikipedia’s article on same-sex marriage in the "further reading" list of Bill C-38.[4] Noncomprehensive lists of such uses are maintained by Wikipedians. [5]

Language editions

Wikipedia's article count has grown quickly in several of the major language editions.


Wikipedia’s article count has grown quickly in several of the major language editions.

Wikipedia encompasses 123 "active" language editions (100+ articles) as of January 2006.[6] Its five largest editions are, in descending order, English, German, French, Polish and Japanese. In total, Wikipedia contains 211 language editions of varying states with a combined 3.5 million articles.[7]

Language editions operate independently of one another. Editions are not bound to the content of other language editions or direct translations of each other; nor are articles on the same subject required to be translations of each other. Automated translation of articles is explicitly disallowed, though multi-lingual editors of sufficient fluency are encouraged to translate articles by hand. The various language editions are held to global policies such as "neutral point of view". Articles and images are nonetheless shared between Wikipedia editions, the former through pages to request translations organized on many of the larger language editions, and the latter through the Wikimedia Commons repository. Translated articles represent only a small portion of articles in any edition.[8]

The following is a list of the large editions, sorted by number of articles as of 1 March 2006. (The article count, however, is a limited metric for comparing the editions. For instance, in some Wikipedia versions nearly half of the articles are short articles created automatically by robots. [6])

Almost all visitors may edit Wikipedia’s content, and registered users can create new articles and have their changes instantly displayed. Wikipedia is built on the expectation that collaboration among users will improve articles over time, in much the same way that open-source software develops. Although many users may tend to add nonsense to the encyclopedia, flaws and unvalid comments will be found and deleted immediately. Further, this real-time, collaborative model allows rapid updating of existing topics and introduction of new topics. The authors need not have any expertise or formal qualifications in the subjects which they edit, and users are warned that their contributions may be "edited mercilessly and redistributed at will" by anyone who so wishes. Its articles are not controlled by any particular user or editorial group. Decision-making on the content and editorial policies of Wikipedia is instead done by consensus and, occasionally, by vote. Jimmy Wales retains final judgement on Wikipedia policies and user guidelines.[9]

By the nature of its openness, "edit wars" and prolonged disputes often occur when editors do not agree.[10] A few members of its community have explained its editing process as a collaborative work, a "socially Darwinian evolutionary process"[11], but this is not generally considered by the community to be an accurate self-description. Articles are always subject to editing, unless the article is protected for a short time due to vandalism or revert wars; therefore, Wikipedia does not declare any article finished. Some users attempt to enter malicious or amusing but irrelevant information, but changes of this sort are normally removed quickly.

Regular users often maintain a "watchlist" of articles of interest to them, so that they are immediately shown which of these articles have changed since their last log in. This allows monitoring of daily editing to prevent false information and spam, and also to keep up with other editors’ views, or updates, of the subjects on the watchlist.

Because of the wiki-principle, most edits of Wikipedia articles are kept within an edit history which can be viewed by everyone. Exceptions include whole articles which are deleted (their histories are no longer available to anyone other than Wikipedia administrators), and revisions of articles which may contain libellous statements, copyright violations, or other content which may incur legal liability or which may be highly detrimental to the project. As a result, Wikipedia is the first major encyclopedia where everybody can see how an article evolved over time and whether the content of an article was ever controversial. Other than the exceptions noted above, all controversial standpoints which were once voiced and afterwards deleted – and even simple vandalism – remain visible for everyone, providing additional information about the article’s topic and its degree of controversy, and adding the dimension of time to every article.

Wikipedia began as a complementary project for Nupedia, a free online encyclopedia project whose articles were written by experts through a formal process. Nupedia was founded on 9 March 2000 under the ownership of Bomis, Inc, a Web portal company. Its principal figures were Jimmy Wales, Bomis CEO, and Larry Sanger, editor-in-chief for Nupedia and later Wikipedia. Nupedia was described by Sanger as differing from existing encyclopedias in being open content; not having size limitations, as it was on the Internet; and being free of bias, due to its public nature and potentially broad base of contributors.[12] Nupedia had a seven-step review process by appointed subject-area experts, but later came to be viewed as too slow for producing a limited number of articles. Funded by Bomis, there were initial plans to recoup its investment by the use of advertisements.[12] It was licensed under its own Nupedia Open Content License initially, switching to the GNU Free Documentation License prior to Wikipedia’s founding at the urging of Richard Stallman.

Wikipedia was formally launched on 15 January 2001, as a single English-language edition at, and announced by Sanger on the Nupedia mailing list.[14] It had been, from 10 January, a feature of in which the public could write articles that could be incorporated into Nupedia after review. It was relaunched off-site after Nupedia’s Advisory Board of subject experts disapproved of its production model.[15] Wikipedia thereafter operated as a standalone project without control from Nupedia. Its policy of "neutral point-of-view" was codified in its initial months, though it is similar to Nupedia’s earlier "nonbias" policy. There were otherwise few rules initially. Wikipedia gained early contributors from Nupedia, Slashdot postings, and search engine indexing. It grew to approximately 20,000 articles among 18 language editions by the end of its first year. It had 26 language editions by the end of 2002, 46 by the end of 2003, and 161 by the end of 2004.[16] Nupedia and Wikipedia coexisted until the former’s servers went down, permanently, in 2003, and its text was incorporated into Wikipedia.

Wales and Sanger attribute the concept of using a wiki to Ward Cunningham’s WikiWikiWeb or Portland Pattern Repository. Wales mentioned that he heard the concept first from Jeremy Rosenfeld, an employee of Bomis who showed him the same wiki, in December 2000,[17] but it was after Sanger heard of its existence from Ben Kovitz, a regular at this wiki, in January 2001,[15] and proposed a creation of a wiki for Nupedia to Wales that Wikipedia’s history started. Under a similar concept of free content, though not wiki production, the GNUPedia project existed alongside Nupedia early in its history. It subsequently became inactive and its creator, free-software figure Richard Stallman, lent his support to Wikipedia.[18]

Citing fear of commercial advertising and lack of control in a perceived English-centric Wikipedia, users of the Spanish Wikipedia forked from Wikipedia to create the Enciclopedia Libre in February 2002. Later that year, Wales announced that Wikipedia would not display advertisements, and moved its website to Projects have since forked from Wikipedia’s content for editorial reasons, such as Wikinfo, which abandoned "neutral point-of-view" in favor of multiple complementary articles written from a "sympathetic point-of-view".

From Wikipedia and Nupedia, the Wikimedia Foundation was created on June 20, 2003.[19] Wikipedia and its sister projects thereafter operated under this non-profit organization. Wikipedia’s first sister project, "In Memoriam: September 11 Wiki" had been created in October 2002 to detail the September 11, 2001 attacks; Wiktionary, a dictionary project, was launched in December 2002; Wikiquote, a collection of quotes, a week after Wikimedia launched; and Wikibooks, a collection of collaboratively-written free books, the next month. Wikimedia has since started a number of other projects, detailed below.

Wikipedia has traditionally measured its status by article count. In its first two years, it grew at a few hundred or fewer new articles per day; by 2004, this had accelerated to 1,000 to 3,000 per day across all editions. The English Wikipedia reached a 100,000 article milestone on January 22 2003[20]. Wikipedia reached its one millionth article among 105 language editions on September 20, 2004,[21] while the English edition alone reached its 500,000th on March 18 2005[22]. Less than a year later the figure had doubled, with the millionth article in the English edition created on March 1 2006[23]; meanwhile, the millionth user registration had been made just 2 days before.

The Wikimedia Foundation applied to the United States Patent and Trademark Office to trademark Wikipedia® on September 17, 2004. The mark was granted registration status on January 10, 2006. Trademark protection was accorded by Japan on December 16, 2004 and in the European Union on January 20, 2005. Technically a servicemark, the scope of the mark is for: "Provision of information in the field of general encyclopedic knowledge via the Internet".

There are currently plans to license the usage of the Wikipedia trademark for some products like books or DVDs.[24] The German Wikipedia will be printed in its entirety by Directmedia, in 100 volumes of 800 pages each. Publication will begin in October 2006 and finish in 2010.

Wikipedia is run by MediaWiki free software on a cluster of dedicated servers located in Florida and four other locations around the world. MediaWiki is Phase III of the program’s software. Originally, Wikipedia ran on UseModWiki by Clifford Adams (Phase I). At first it required CamelCase for links; later it was also possible to use double brackets. Wikipedia began running on a PHP wiki engine with a MySQL database in January 2002. This software, Phase II, was written specifically for the Wikipedia project by Magnus Manske. Several rounds of modifications were made to improve performance in response to increased demand. Ultimately, the software was rewritten again, this time by Lee Daniel Crocker. Instituted in July 2002, this Phase III software was called MediaWiki. It was licensed under the GNU General Public License and used by all Wikimedia projects.

Wikipedia was served from a single server until 2003, when the server setup was expanded into a distributed multitier architecture. In January 2005, the project ran on 39 dedicated servers located in Florida. This configuration included a single master database server running MySQL, multiple slave database servers, 21 web servers running the Apache software, and seven Squid cache servers. By September 2005, its server cluster had grown to around 100 servers in four locations around the world.

Page requests are processed by first passing to a front-end layer of Squid caching servers. Requests that cannot be served from the Squid cache are sent to two load-balancing servers running the Perlbal software, which then pass the request to one of the Apache web servers for page-rendering from the database. The web servers serve pages as requested, performing page rendering for all the Wikipedias. To increase speed further, rendered pages for anonymous users are cached in a filesystem until invalidated, allowing page rendering to be skipped entirely for most common page accesses. Wikimedia has begun building a global network of caching servers with the addition of three such servers in France. A new Dutch cluster is also online now. In spite of all this, Wikipedia page load times remain quite variable. The ongoing status of Wikipedia’s website is posted by users at a status page on OpenFacts.

Wikipedia has been both praised and criticized for being open to editing by anyone. Proponents contend that open editing improves quality over time while critics allege that non-expert editing undermines quality.

Wikipedia has been criticized for a perceived lack of reliability, comprehensiveness, and authority. It is considered to have no or limited utility as a reference work among many librarians, academics, and the editors of more formally written encyclopedias. A website called Wikipedia Watch has been created to denounce Wikipedia as having "…a massive, unearned influence on what passes for reliable information."

Some argue that allowing anyone to edit makes Wikipedia an unreliable work. Wikipedia contains no formal peer review process for fact-checking, and the editors themselves may not be well-versed in the topics they write about. In a 2004 interview with The Guardian, librarian Philip Bradley said that he would not use Wikipedia and is "not aware of a single librarian who would. The main problem is the lack of authority. With printed publications, the publishers have to ensure that their data are reliable, as their livelihood depends on it. But with something like this, all that goes out the window" (Waldman, 2004). Similarly, Encyclopædia Britannica’s executive editor, Ted Pappas, was quoted in The Guardian as saying: "The premise of Wikipedia is that continuous improvement will lead to perfection. That premise is completely unproven."[26] On October 24, 2005, The Guardian published an article "Can you trust Wikipedia?" where a group of experts critically reviewed entries for their fields. Discussing Wikipedia as an academic source, Danah Boyd said in 2005 that "[i]t will never be an encyclopedia, but it will contain extensive knowledge that is quite valuable for different purposes".[27]

Be Bold has become the unofficial slogan of Wikipedia.


Be Bold has become the unofficial slogan of Wikipedia.

Academic circles have not been exclusively dismissive of Wikipedia as a reference. Wikipedia articles have been referenced in "enhanced perspectives" provided on-line in Science. The first of these perspectives to provide a hyperlink to Wikipedia was "A White Collar Protein Senses Blue Light" (Linden, 2002), and dozens of enhanced perspectives have provided such links since then. However, these links are offered as background sources for the reader, not as sources used by the writer, and the "enhanced perspectives" are not intended to serve as reference material themselves.

In a 2004 piece called "The Faith-Based Encyclopedia," former Britannica editor Robert McHenry criticized the wiki approach, writing,

[h]owever closely a Wikipedia article may at some point in its life attain to reliability, it is forever open to the uninformed or semiliterate meddler… The user who visits Wikipedia to learn about some subject, to confirm some matter of fact, is rather in the position of a visitor to a public restroom. It may be obviously dirty, so that he knows to exercise great care, or it may seem fairly clean, so that he may be lulled into a false sense of security. What he certainly does not know is who has used the facilities before him.[28]

In response to this criticism, proposals have been made to provide various forms of provenance for material in Wikipedia articles; see for example Wikipedia:Provenance. The idea is to provide source provenance on each interval of text in an article and temporal provenance as to its vintage. In this way a reader can know "who has used the facilities before him" and how long the community has had to process the information in an article to provide calibration on the "sense of security." However, these proposals for provenance are quite controversial (see Wikipedia talk:Provenance). Aaron Krowne wrote a rebuttal article in which he criticized McHenry’s methods, and labeled them "FUD," the marketing technique of "fear, uncertainty, and doubt."[29]

Former Nupedia editor-in-chief Larry Sanger criticized Wikipedia in late 2004 for having, according to Sanger, an "anti-elitist" philosophy of active contempt for expertise.[30]

Wikipedia’s editing process assumes that exposing an article to many users will result in accuracy. Referencing Linus’ law of open-source development, Sanger stated earlier: "Given enough eyeballs, all errors are shallow."[31] Technology figure Joi Ito wrote on Wikipedia’s authority, "[a]lthough it depends a bit on the field, the question is whether something is more likely to be true coming from a source whose resume sounds authoritative or a source that has been viewed by hundreds of thousands of people (with the ability to comment) and has survived."[32] Conversely, in an informal test of Wikipedia’s ability to detect misinformation, its author remarked that its process "isn’t really a fact-checking mechanism so much as a voting mechanism", and that material which did not appear "blatantly false" may be accepted as true.[33]

Wikipedia has been accused of deficiencies in comprehensiveness because of its voluntary nature, and of reflecting the systemic biases of its contributors. Encyclopædia Britannica editor-in-chief Dale Hoiberg has argued that "people write of things they’re interested in, and so many subjects don’t get covered; and news events get covered in great detail. The entry on Hurricane Frances was five times the length of that on Chinese art, and the entry on Coronation Street was twice as long as the article on Tony Blair."[26] (As of December 2005, this is no longer the case.) Former Nupedia editor-in-chief Larry Sanger stated in 2004, "when it comes to relatively specialized topics (outside of the interests of most of the contributors), the project’s credibility is very uneven."[30]

The English-language website also suffers from frequent timeouts, server errors and occasional downtime due to heavy user traffic. These problems have had a negative impact on Wikipedia’s desired image as a fast and reliable source of information.

It has been praised for, as a wiki, allowing articles to be updated or created in response to current events. For example, the then-new article on the 2004 Indian Ocean earthquake on its English edition was cited often by the press shortly after the incident. Its editors have also argued that, as a website, Wikipedia is able to include articles on a greater number of subjects than print encyclopedias may.[34]

Microsoft Encarta has started to solicit comments from readers in attempt to improve the accuracy and timeliness of its encyclopedia. Encarta Feedback allows any user to propose revisions for review by their staff.[35]

The German computing magazine c’t performed a comparison of Brockhaus Premium, Microsoft Encarta, and Wikipedia in October 2004: Experts evaluated 66 articles in various fields. In overall score, Wikipedia was rated 3.6 out of 5 points ("B-"), Brockhaus Premium 3.3, and Microsoft Encarta 3.1.[36] In an analysis of online encyclopedias, Indiana University professors Emigh and Herring wrote that "Wikipedia improves on traditional information sources, especially for the content areas in which it is strong, such as technology and current events."[37]. The journal Nature reported in 2005 that science articles in Wikipedia were comparable in accuracy to those in Encyclopedia Britannica. Wikipedia had an average of four mistakes per article; Britannica contained three. Of eight "serious errors" found — including misinterpretations of important concepts — four came from each source.[38]. On March 24, 2006, Britannica provided a rebuttal labeling the study "fatally flawed". [39].

At the end of 2005, controversy erupted after journalist John Seigenthaler Sr. found that his biography had been written largely as a hoax about Seigenthaler. This led to the decision to restrict the ability to start articles to registered users.


The Wikipedia community consists of users who are proportionally few, but highly active. Emigh and Herring argue that "a few active users, when acting in concert with established norms within an open editing system, can achieve ultimate control over the content produced within the system, literally erasing diversity, controversy, and inconsistency, and homogenizing contributors’ voices." Editors on Wikinfo, a fork of Wikipedia, similarly argue that new or controversial editors to Wikipedia are often unjustly labeled "trolls" or "problem users" and blocked from editing.[40] Its community has also been criticized for responding to complaints regarding an article’s quality by advising the complainer to fix the article.[41]

In a page on researching with Wikipedia, its authors argue that Wikipedia is valuable for being a social community. That is, authors can be asked to defend or clarify their work, and disputes are readily seen.[42] Wikipedia editions also often contain reference desks in which the community answers questions.


Wikipedia won two major awards in May 2004[43]: The first was a Golden Nica for Digital Communities, awarded by Prix Ars Electronica; this came with a 10,000 euro grant and an invitation to present at the PAE Cyberarts Festival in Austria later that year. The second was a Judges’ Webby award for the "community" category. Wikipedia was also nominated for a "Best Practices" Webby. In September 2004, the Japanese Wikipedia was awarded a Web Creation Award from the Japan Advertisers Association. This award, normally given to individuals for great contributions to the Web in Japanese, was accepted by a long-standing contributor on behalf of the project. Wikipedia has received plaudits from sources including BBC News, Washington Post, The Economist, Newsweek, Los Angeles Times, Science, The Guardian, Chicago Sun-Times, The Times (London), Toronto Star, Globe and Mail, The Financial Times, Time Magazine, Irish Times, Reader’s Digest and The Daily Telegraph.


During December 2005, Wikipedia had about 27,000 users who made at least five edits that month; 17,000 of these active users worked on the English edition.[44] A more active group of about 4,000 users made more than 100 edits per month, over half of these users having worked in the English edition. According to Wikimedia, one-quarter of Wikipedia’s traffic comes from users without accounts, who are less likely to be editors.[45]

Maintenance tasks are performed by a group of volunteer developers, stewards, bureaucrats, and administrators, which number in the hundreds. Administrators are the largest such group, privileged with the ability to prevent articles from being edited, delete articles, or block users from editing in accordance with community policy. Many users have been temporarily or permanently blocked from editing Wikipedia. Vandalism or the minor infraction of policies may result in a warning or temporary block, while long-term or permanent blocks for prolonged and serious infractions are given by Jimmy Wales or, on its English edition, an elected Arbitration Committee.

Former Nupedia editor-in-chief Larry Sanger has said that having the GFDL license as a "guarantee of freedom is a strong motivation to work on a free encyclopedia."[46] In a study of Wikipedia as a community, Economics professor Andrea Ciffolilli argued that the low transaction costs of participating in wiki software create a catalyst for collaborative development, and that a "creative construction" approach encourages participation.[47] Wikipedia has been viewed as a social experiment in anarchy, democracy, or communism. Its founder has replied that it is not intended as one, though that is a consequence.[48] Critics of Wikipedia have also viewed it as an oligarchy which is controlled primarily by its administrators, stewards, and bureaucrats, or simply by a small number of its contributors. Daniel Brandt of Wikipedia Watch has referred to Jimbo Wales as the "dictator" of Wikipedia; however, most Wikipedia users do not consider Wales to be a dictator.