Wikipedia:Training/core/Verifiability

Beyond the five pillars, there are a few more important policies and guidelines to keep in mind. First: Verifiability Since Wikipedia is the online encyclopedia that anyone can edit, for content to remain in Wikipedia it must be verifiable, which means that people reading and editing the encyclopedia can check that information comes from a reliable source.


 * Although all content must be verifiable, not all content must be actually verified by citation to a reliable source. You do not normally need to cite a source, for example, to corroborate that the sky is blue. Nevertheless, citing reliable sources for all significant facts in an article is the recommended practice and Wikipedia's best articles, its featured content, must do so to meet the criteria for achieving that status.


 * There are four types of material that must be cited to a reliable source, using an inline citation, in order to be included:
 * 1) All quotations;
 * 2) Any statement that has been challenged (e.g., by being removed, questioned on the talk page, or tagged with, or any similar tag);
 * 3) Any statement that you believe is likely to be challenged; and
 * 4) Contentious material, whether negative, positive, or neutral, about living persons.