Wikipedia is an online encyclopedia that is free to read and edit. It contains over 66 million articles in more than 340 languages, collaboratively written and maintained by more than 250,000 active volunteer editors called Wikipedians. As of 2025, it is one of the 10 most visited sites in the world, with 1.5 billion unique monthly site visits.
Hours of research by our editors, distilled into minutes of clarity.
Nearly 300,000 volunteers worldwide help write, edit, and fact-check articles on the site in real-time, striving to ensure content is authored from a neutral point of view. All pages are freely accessible and must include citations to reliable, published sources.
As of 2024, the site is 90 times larger than the 120-volume Encyclopedia Britannica, but its automation tools can often catch and revert inaccurate edits within 60 seconds. Its low-bandwidth, adless pages have allowed it to handle millions of site visits daily, even during times of high internet traffic.
Unlike a journal article, which may be reviewed by up to three people before publication, popular Wikipedia pages may be reviewed thousands of times by editors, potentially enhancing their reliability. Less reviewed articles still require reliable third-party sources and remain subject to verification by bots and administrators who can undo edits.
The record had been held for approximately six centuries by the Yongle Encyclopedia, which was commissioned by the Yongle Emperor of the Ming dynasty in 1403 to preserve information from ancient and imperial China. The text comprised 22,937 manuscript rolls in 11,095 volumes.
Studies from Nature, The Guardian, the Journal of Clinical Oncology, and the Canadian Library Association, among others, did not identify significant errors, particularly in articles related to academic topics. The site is still considered an exploratory, tertiary source subject to systemic biases from its human editors, especially within controversial topics.
A 2024 study by the University of Barcelona found that 71.4% of all English biographies that appear on the front page are about men, and approximately one in five editors are women. Researchers suggest systemic imbalances in society further diminish women's contributions to the site by leaving them with less time to defend edits during editorial disputes.
The largest Wikipedia language edition features over 7 million articles, followed by the Cebuano edition (over 6 million) and the German edition (over 3 million). The longest article is the "2025 in women's road cycling" page, and the most edited is the list of personnel from World Wrestling Entertainment.
Nupedia was launched in 2000 by internet entrepreneur Jimmy Wales and internet project developer Lawrence Sanger, only publishing articles written by experts after a cumbersome seven-step review process. The two developed Wikipedia to allow the public to write articles for future review, but shifting to self-moderation contributed to Sanger's departure in 2002.
Computer programmer Ward Cunningham created the WikiWikiWeb online application based on an offline system that helped track how ideas moved through his company. The application enabled users to collaborate and edit website content through a web browser, as well as link pages without requiring a structured navigation scheme.
Since its founding in 2003, the nonprofit has provided financial, legal, and infrastructure support to Wikipedia and its sister projects (e.g., Wikinews), primarily by managing donations, which average $11, from readers. Additional funding comes from gifts exceeding $1,000, the Wikimedia Endowment, and providing Wikipedia content for commercial use.
Since our ancient human relatives began using stone tools to perform tasks, humans have harnessed scientific knowledge and new technologies to expand the boundaries of our understanding of the natural world. From quantum computing and microplastics to artificial intelligence and memory, explore these topics and more with our concise yet informative overviews and expert-curated resources.