The free encyclopedia that anyone can edit

Wikipedia is a multilingual online encyclopedia created and maintained as an open collaboration project by a community of volunteer editors using a wiki-based editing system. It is the largest and most popular general reference work on the World Wide Web, and is one of the most popular websites ranked by Alexa as of January 2020. It features exclusively free content and no commercial ads, and is owned and supported by the Wikimedia Foundation, a non-profit organization funded primarily through donations.  [Wikipedia API]

Wikipedia was launched on January 15, 2001, by Jimmy Wales and Larry Sanger. Sanger coined its name, as a portmanteau of "wiki" (the Hawaiian word for "quick") and "encyclopedia". Initially an English-language encyclopedia, versions of Wikipedia in other languages were quickly developed. With at least 6,034,632 articles, the English Wikipedia is the largest of the more than 290 Wikipedia encyclopedias. Overall, Wikipedia comprises more than 40 million articles in 301 different languages and by February 2014 it had reached 18 billion page views and nearly 500 million unique visitors per month.

In 2005, Nature published a peer review comparing 42 hard science articles from Encyclopædia Britannica and Wikipedia and found that Wikipedia's level of accuracy approached that of Britannica, although critics suggested that it might not have fared so well in a similar study of a random sampling of all articles or one focused on social science or contentious social issues. The following year, Time magazine stated that the open-door policy of allowing anyone to edit had made Wikipedia the biggest and possibly the best encyclopedia in the world, and was a testament to the vision of Jimmy Wales.

Wikipedia has been criticized for exhibiting systemic bias, for presenting a mixture of "truth, half truth, and some falsehoods", and for being subject to manipulation and spin in controversial topics. Wikipedia has also been criticized for gender bias, particularly on its English-language site, where the dominant majority of editors are male. However, Edit-a-thons have been held to encourage female editors and increase the coverage of women's topics. Facebook announced that by 2017 it would help readers detect fake news by suggesting links to related Wikipedia articles. YouTube announced a similar plan in 2018.



Other collaborative online encyclopedias were attempted before Wikipedia, but none were as successful.Wikipedia began as a complementary project for Nupedia, a free online English-language encyclopedia project whose articles were written by experts and reviewed under a formal process. It was founded on March 9, 2000, under the ownership of Bomis, a web portal company. Its main figures were Bomis CEO Jimmy Wales and Larry Sanger, editor-in-chief for Nupedia and later Wikipedia. Nupedia was initially licensed under its own Nupedia Open Content License, but even before Wikipedia was founded, Nupedia switched to the GNU Free Documentation License at the urging of Richard Stallman. Wales is credited with defining the goal of making a publicly editable encyclopedia, while Sanger is credited with the strategy of using a wiki to reach that goal. On January 10, 2001, Sanger proposed on the Nupedia mailing list to create a wiki as a "feeder" project for Nupedia.

Launch and early growth

The domains and were registered on January 12, 2001 and January 13, 2001 respectively, and Wikipedia was launched on January 15, 2001, as a single English-language edition at, and announced by Sanger on the Nupedia mailing list. Wikipedia's policy of "neutral point-of-view" was codified in its first few months. Otherwise, there were relatively few rules initially and Wikipedia operated independently of Nupedia. Originally, Bomis intended to make Wikipedia a business for profit.

Wikipedia gained early contributors from Nupedia, Slashdot postings, and web search engine indexing. Language editions were also created, with a total of 161 by the end of 2004. Nupedia and Wikipedia coexisted until the former's servers were taken down permanently in 2003, and its text was incorporated into Wikipedia. The English Wikipedia passed the mark of two million articles on September 9, 2007, making it the largest encyclopedia ever assembled, surpassing the 1408 Yongle Encyclopedia, which had held the record for almost 600 years.

Citing fears of commercial advertising and lack of control in Wikipedia, users of the Spanish Wikipedia forked from Wikipedia to create the Enciclopedia Libre in February 2002. These moves encouraged Wales to announce that Wikipedia would not display advertisements, and to change Wikipedia's domain from to Brion Vibber applied the change on August 15, 2002.

Though the English Wikipedia reached three million articles in August 2009, the growth of the edition, in terms of the numbers of new articles and of contributors, appears to have peaked around early 2007. Around 1,800 articles were added daily to the encyclopedia in 2006; by 2013 that average was roughly 800. A team at the Palo Alto Research Center attributed this slowing of growth to the project's increasing exclusivity and resistance to change. Others suggest that the growth is flattening naturally because articles that could be called "low-hanging fruit"—topics that clearly merit an article—have already been created and built up extensively.

In November 2009, a researcher at the Rey Juan Carlos University in Madrid found that the English Wikipedia had lost 49,000 editors during the first three months of 2009; in comparison, the project lost only 4,900 editors during the same period in 2008. The Wall Street Journal cited the array of rules applied to editing and disputes related to such content among the reasons for this trend. Wales disputed these claims in 2009, denying the decline and questioning the methodology of the study. Two years later, in 2011, Wales acknowledged the presence of a slight decline, noting a decrease from "a little more than 36,000 writers" in June 2010 to 35,800 in June 2011. In the same interview, Wales also claimed the number of editors was "stable and sustainable". A 2013 article titled "The Decline of Wikipedia" in MIT's Technology Review questioned this claim. The article revealed that since 2007, Wikipedia had lost a third of its volunteer editors, and those still there have focused increasingly on minutiae. In July 2012, The Atlantic reported that the number of administrators is also in decline. In the November 25, 2013, issue of New York magazine, Katherine Ward stated "Wikipedia, the sixth-most-used website, is facing an internal crisis".


In January 2007, Wikipedia entered for the first time the top-ten list of the most popular websites in the US, according to comScore Networks. With 42.9 million unique visitors, Wikipedia was ranked number 9, surpassing The New York Times (#10) and Apple (#11). This marked a significant increase over January 2006, when the rank was number 33, with Wikipedia receiving around 18.3 million unique visitors. As of September 2019, Wikipedia has rank 9 among websites in terms of popularity according to Alexa Internet. In 2014, it received eight billion pageviews every month. On February 9, 2014, The New York Times reported that Wikipedia has 18 billion page views and nearly 500 million unique visitors a month, "according to the ratings firm comScore".

On January 18, 2012, the English Wikipedia participated in a series of coordinated protests against two proposed laws in the United States Congress—the Stop Online Piracy Act (SOPA) and the PROTECT IP Act (PIPA)—by blacking out its pages for 24 hours. More than 162 million people viewed the blackout explanation page that temporarily replaced Wikipedia content.

Loveland and Reagle argue that, in process, Wikipedia follows a long tradition of historical encyclopedias that accumulated improvements piecemeal through "stigmergic accumulation".

On January 20, 2014, Subodh Varma reporting for The Economic Times indicated that not only had Wikipedia's growth stalled, it "had lost nearly ten percent of its page views last year. There was a decline of about two billion between December 2012 and December 2013. Its most popular versions are leading the slide: page-views of the English Wikipedia declined by twelve percent, those of German version slid by 17 percent and the Japanese version lost nine percent." Varma added that, "While Wikipedia's managers think that this could be due to errors in counting, other experts feel that Google's Knowledge Graphs project launched last year may be gobbling up Wikipedia users." When contacted on this matter, Clay Shirky, associate professor at New York University and fellow at Harvard's Berkman Center for Internet & Society indicated that he suspected much of the page view decline was due to Knowledge Graphs, stating, "If you can get your question answered from the search page, you don't need to click [any further]."

By the end of December 2016, Wikipedia was ranked fifth in the most popular websites globally.

In January 2013, 274301 Wikipedia, an asteroid, was named after Wikipedia; in October 2014, Wikipedia was honored with the Wikipedia Monument; and, in July 2015, Wikipedia became available as 7,473 books for $500,000. In 2019, a species of flowering plant was named Viola wikipedia.

In April 2019, an Israeli lunar lander, Beresheet, crash landed on the surface of the Moon carrying a copy of nearly all of the English Wikipedia engraved on thin nickel plates; experts say the plates likely survived the crash.

In June 2019, scientists reported that all 16 GB of article text from the English Wikipedia have been encoded into synthetic DNA.