WP:V redirects here. For the official policy about vandalism, use WP:VAND.

Wikipedia should only publish material that is verifiable and is not original research.

The goal of Wikipedia is to become a complete and reliable encyclopedia. Verifiability is the key to becoming a reliable resource, so editors should cite credible sources so that their edits can be easily verified.

Wikipedia:Verifiability is one of three of Wikipedia's content-guiding policy pages. The other two are No original research and Neutral point of view. Together, these three policies determine the type and quality of material that is acceptable in the main namespace.

When adding information

Fact checking is time consuming and not particularly rewarding. It is unfair to make later editors dig for sources to check your work, particularly when the initial content is questionable. Those who write articles likely to be deemed in need of fact checking, for whatever reason, should expect to assist by providing references, ideally when the article is first written. Because of this, it's important to make it easy to verify the accuracy and neutrality of your content. Citing your sources is an important part of this, but not the only factor. Another good rule of thumb is to be specific (and avoid weasel words). For example:

A human rights spokesman said that the incident was part of a wider pattern of violence in the region

This is difficult to verify, because it's hard to know where to start. Many spokespeople may have commented about the incident on many dates and on many occasions, and it's unreasonable to expect someone to check all these statements looking for the one that matches. A better phrasing would be:

Eliza Twisk, of Amnesty International, described the situation in an interview with Channel 4 news on July 8 [1]

This is easy to verify: one could contact Eliza Twisk, or Channel 4, or Amnesty International. As the exact quote is given, rather than a paraphrase, this can be fed into various search engines. Finally, a URL of a transcript is given.

Other Languages
беларуская (тарашкевіца)‎: Вікіпэдыя:Магчымасьць праверкі
Bahasa Indonesia: Wikipedia:Pemastian
Bahasa Melayu: Wikipedia:Pengesahan
Baso Minangkabau: Wikipedia:Pamastian
srpskohrvatski / српскохрватски: Wikipedia:Proverljivost