|This page in a nutshell: Although citing sources is an important part of editing Wikipedia, there is no need to cite information that is already obvious.|
Verifiability is an important and core policy of Wikipedia. Article content should be backed up by reliable sources wherever needed to show that the presentation of material on Wikipedia is consistent with the views that are presented in scholarly discourse or the world at large. Such sources help to improve the encyclopedia.
However, many editors misunderstand the citation policy, seeing it as a tool to enforce, reinforce, or cast doubt upon a particular point of view in a content dispute, rather than as a means to verify Wikipedia's information. This can lead to several mild forms of disruptive editing which are better avoided. Ideally, common sense would always be applied but Wiki-history shows this is unrealistic. Therefore, this essay gives some practical advice.
Pedantry, and other didactic arguments
Sometimes editors will insist on citations for material simply because they dislike it or prefer some other material, not because the material in any way needs verification. For example, an editor may demand a citation for the fact that most people have five digits on each hand (yes, this really happened). Another may decide that the color of the sky is actually aqua rather than blue, pull out an assortment of verifiable spectrographic analyses and color charts to demonstrate that this position is actually correct, and follow that with a demand that other editors provide equivalent reliable sources for the original statement that the sky is in fact blue. While there are cases where this kind of pedantic insistence is useful and necessary, often it is simply disruptive, and can be countered simply by pointing out that there is no need to verify statements that are patently obvious. If the alternate proposition merits inclusion in the article under other policies and guidelines it should of course be included, but it should in no way be given greater prominence because it is sourced.
Wikipedia has several templates for tagging material that needs verification: inline templates for particular lines, section templates, and article templates. See Wikipedia:Template messages. Sometimes editors will go through an article and add dozens of the inline tags, along with several section and article tags, making the article essentially unreadable (see WP:TAGBOMBING). As a rule, if there are more than 2 or 3 inline tags they should be removed and replaced with a section tag; if there are more than 2 section tags in a section they should be removed and replaced with a single 'Multiple issues' tag. If there are more than two or three sections tagged, those tags should be removed, and the entire article should be tagged.
Verification tags should not be used in a POINTed fashion. Use only those tags necessary to illustrate the problem, and discuss the matter in detail on the talk page.
Citations should be evaluated on the qualities they bring to the article, not on the quantity of citations available. The first 1 or 2 citations supporting a given point are informative; extra citations after that begin to be argumentative. Keep in mind that the purpose of a citation is to guide the reader to external sources where the reader can verify the idea presented, not to prove to other editors the strength of the idea. Extra sources for the same idea should be added to 'Further Reading', 'See Also', or 'External Sources' sections at the bottom of the page, without explicitly being cited in the text.
A common misconception when improving an article, particularly towards Good Article status, is that everything must be cited to an inline source, which leads to comments such as "the end of paragraph 3 is uncited", without specifying why that is an issue. In fact, the Good Article criteria merely state that inline citations are required for "direct quotations, statistics, published opinion, counter-intuitive or controversial statements that are challenged or likely to be challenged, and contentious material relating to living persons". While that covers much, most, or possibly even (in the case of biographies of living people) all content in an article, it does not imply that you must cite everything everywhere for every single article, period.
- Wikipedia:You do need to cite that the sky is blue, the opposing essay discussion.
- Wikipedia:The Pope is Catholic
- Wikipedia:Likely to be challenged
- Wikipedia:Common knowledge
- Wikipedia:Wisps' Law
- Wikipedia:When to cite § When a source may not be needed
- User:Uncle G/On sources and content § There are no exceptions to everything, user essay
- Wikipedia:Why most sentences should be cited, user essay
- Judicial notice, a legal rule that allows irrefutable, well-known facts to be introduced into evidence
- Common knowledge
- Argumentum ad populum
- Wikipedia:Routine calculation