A citation, or reference,^{[note 1]} uniquely identifies a source of information, e.g.:

Wikipedia's verifiability policy requires inline citations for any material challenged or likely to be challenged, and for all quotations, anywhere in article space.

A citation or reference in an article usually has two parts. In the first part, each section of text that is either based on, or quoted from, an outside source is marked as such with an inline citation. This is usually displayed as a superscript footnote number: ^[1] The second necessary part of the citation or reference is the list of full references, which provides complete, formatted detail about the source, so that anyone reading the article can find it and verify it.

This page explains how to place and format both parts of the citation. Each article should use one citation method or style throughout. If an article already has citations, preserve consistency by using that method or seek consensus on the talk page before changing it (the principle is reviewed at § Variation in citation methods). While you should try to write citations correctly, what matters most is that you provide enough information to identify the source. Others will improve the formatting if needed. See: "Help:Referencing for beginners", for a brief introduction on how to put references in Wikipedia articles; and cite templates in Visual Editor, about a graphical way for citation, included in Wikipedia.

• An inline citation means any citation added close to the material it supports, for example after the sentence or paragraph, normally in the form of a footnote.
• In-text attribution involves adding the source of a statement to the article text, such as Rawls argues that X.^[5] This is done whenever a writer or speaker should be credited, such as with quotations, close paraphrasing, or statements of opinion or uncertain fact. The in-text attribution does not give full details of the source – this is done in a footnote in the normal way. See In-text attribution below.
• A general reference is a citation that supports content, but is not linked to any particular piece of material in the article through an inline citation. General references are usually listed at the end of the article in a References section. They are usually found in underdeveloped articles, especially when all article content is supported by a single source. They may also be listed in more developed articles as a supplement to inline citations.

Short and full citations

• A full citation fully identifies a reliable source and, where applicable, the place in that source (such as a page number) where the information in question can be found. For example: Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 1. This type of citation is usually given as a footnote, and is the most commonly used citation method in Wikipedia articles.

• A short citation is an inline citation that identifies the place in a source where specific information can be found, but without giving full details of the source. Some Wikipedia articles use it, giving summary information about the source together with a page number. For example, <ref>Rawls 1971, p. 1.</ref>, which renders as Rawls 1971, p. 1.. These are used together with full citations, which are listed in a separate "References" section or provided in an earlier footnote.

Forms of short citations used include author-date referencing (APA style, Harvard style, or Chicago style), and author-title or author-page referencing (MLA style or Chicago style). As before, the list of footnotes is automatically generated in a "Notes" or "Footnotes" section, which immediately precedes the "References" section containing the full citations to the source. Short citations can be written manually, or by using either the {{sfn}} or {{harvnb}} templates or the {{r}} referencing template. (Note that templates should not be added without consensus to an article that already uses a consistent referencing style.) The short citations and full citations may be linked so that the reader can click on the short note to find full information about the source. See the template documentation for details and solutions to common problems. For variations with and without templates, see wikilinks to full references. For a set of realistic examples, see these.

This is how short citations look in the edit box:

The Sun is pretty big,<ref>Miller 2005, p. 23.</ref> but the Moon is not so big.<ref>Brown 2006, p. 46.</ref> The Sun is also quite hot.<ref>Miller 2005, p. 34.</ref>

== Notes ==
{{reflist}}

== References ==
* Brown, Rebecca (2006). "Size of the Moon", ''Scientific American'', 51 (78).
* Miller, Edward (2005). ''The Sun''. Academic Press.

This is how they look in the article:

Shortened notes using titles rather than publication dates would look like this in the article:

When using manual links it is easy to introduce errors such as duplicate anchors and unused references. The script User:Trappist the monk/HarvErrors will show many related errors. Duplicate anchors may be found by using the W3C Markup Validation Service.

By citing sources for Wikipedia content you enable users to verify that the cited information is supported by reliable sources – improving the credibility of Wikipedia while showing that the content is not original research. You also help users find additional information on the subject; and by giving attribution you avoid plagiarising the source of your words or ideas.

In particular, sources are needed for material that is challenged or likely to be challenged. If reliable sources cannot be found for challenged material, it is likely to be removed from the article. Sources are also required when quoting someone, with or without quotation marks, or closely paraphrasing a source. But the need to cite sources is not limited to those situations: editors are always encouraged to add or improve citations for any information in an article.

Citations are especially desirable for statements about living persons, particularly when the statements are contentious or potentially defamatory. In accordance with the biography of living persons policy, unsourced information of this type is likely to be removed on sight.

Multimedia

For an image or other media file, details of its origin and copyright status should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself, or for text that merely identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg).

When not to cite

Citations are not used on disambiguation pages (sourcing for the information given there should be done in the target articles). Citations are often omitted from the lead section of an article, insofar as the lead summarizes information for which sources are given later in the article, although quotations and controversial statements, particularly if about living persons, should be supported by citations even in the lead. See WP:LEADCITE for more information.

Consecutive cites of the same source

Per WP:PAIC, citations should be placed at the end of the text that they support. Material that is repeated multiple times in a paragraph does not require an inline citation for every mention. If you say an elephant is a mammal more than once, provide one only at the first instance. Avoid cluttering text with redundant citations like this:

Elephants are large^[1] land^[2] mammals^[3] ... Elephants' teeth^[4] are very different^[4] from those of most other mammals.^[3][4] Unlike most mammals,^[3] which grow baby teeth^[5] and then replace them with a permanent set of adult teeth,^[4] elephants have cycles of tooth^[5] rotation throughout their entire^[6] lives.^[4]

This does not apply to lists or tables, nor does it apply when multiple sources support different parts of a paragraph or passage. Citation requirements for WP:DYK may require a citation to be inserted (for the duration of the DYK listing) even within a passage completely cited to the same sources.^[a]

Inline citations allow the reader to associate a given piece of material in an article with the specific reliable source(s) that support it. Inline citations are added using footnotes, long or short.

How to place an inline citation using ref tags

To create a footnote, use the <ref>...</ref> syntax at the appropriate place in the article text, for example:

• Justice is a human invention.<ref>Rawls, John. ''A Theory of Justice''. Harvard University Press, 1971, p. 1.</ref> It ...

which will be displayed as something like:

• Justice is a human invention.^[1] It ...

It will also be necessary to generate the list of footnotes (where the citation text is actually displayed); for this, see the previous section.

As in the above example, citation markers are normally placed after adjacent punctuation such as periods (full stops) and commas. For exceptions, see the WP:Manual of Style § Punctuation and footnotes. Note also that no space is added before the citation marker. Citations should not be placed within, or on the same line as, section headings.

The citation should be added close to the material it supports, offering text–source integrity. If a word or phrase is particularly contentious, an inline citation may be added next to that word or phrase within the sentence, but it is usually sufficient to add the citation to the end of the clause, sentence, or paragraph, so long as it's clear which source supports which part of the text.

Avoiding clutter

Inline references can significantly bloat the wikitext in the edit window and can become confusing and difficult to manage. There are two main methods to avoid clutter in the edit window:

• Using list-defined references by collecting the full citation code within the reference list template {{reflist}}, and then inserting them in the text with a shortened reference tag, for example <ref name="Smith 2001, p99" />.
• Inserting short citations (see below) that then refer to a full list of source texts

As with other citation formats, articles should not undergo large-scale conversion between formats without consensus to do so.

Note, however, that references defined in the reference list template can no longer be edited with the VisualEditor.

Repeated citations

For multiple use of the same inline citation or footnote, you can use the named references feature, choosing a name to identify the inline citation, and typing <ref name="name">text of the citation</ref>. Thereafter, the same named reference may be reused any number of times either before or after the defining use by typing the previous reference name, like this: <ref name="name" />. The use of the slash before the > means that the tag is self-closing, and the </ref> used to close other references must not be used in addition.

The text of the name can be almost anything‍—‌apart from being completely numeric. If spaces are used in the text of the name, the text must be placed within double quotes. Placing all named references within double quotes may be helpful to future editors who do not know that rule. To help with page maintenance, it is recommended that the text of the name have a connection to the inline citation or footnote, for example "author year page": <ref name="Smith 2005 p94">text of the citation</ref>.

Use straight quotation marks " to enclose the reference name. Do not use curly quotation marks “”. Curly marks are treated as another character, not as delimiters. The page will display an error if one style of quotation marks is used when first naming the reference, and the other style is used in a repeated reference, or if a mix of styles is used in the repeated references.

Citing multiple pages of the same source

When an article cites many different pages from the same source, to avoid the redundancy of many big, nearly identical full citations, most Wikipedia editors use one of these options:

• Named references in conjunction with a combined list of page numbers using the |pages= parameter of the {{cite xxx}} templates (most commonly used, but can become confusing for large number of pages)
• Named references in conjunction with the {{rp}} or {{r}} templates to specify the page
• Short citations

The use of ibid., id., or similar abbreviations is discouraged, as they may become broken as new references are added (op. cit. is less problematic in that it should refer explicitly to a citation contained in the article; however, not all readers are familiar with the meaning of the terms). If the use of ibid is extensive, tag the article using the {{ibid}} template.

What information to include

Listed below is the information that a typical inline citation or general reference will provide, though other details may be added as necessary. This information is included in order to identify the source, assist readers in finding it, and (in the case of inline citations) indicate the place in the source where the information is to be found. (If an article uses short citations, then the inline citations will refer to this information in abbreviated form, as described in the relevant sections above.)

In general, the citation information should be cited as it appears in the original source. For example, the album notes from Hurts 2B Human should not be cited as being from the album Hurts to be Human, or an X (formerly Twitter) user named "i😍dogs" should not be cited as "i[love]dogs". Retain the original special glyphs and spelling.

Examples

Books

Citations for books typically include:

• name of author(s)
• title of book
• volume when appropriate
• name of publisher
• place of publication
• date of publication of the edition
• chapter or page numbers cited, if appropriate
• edition, if not the first edition
• ISBN (optional)

Citations for individually authored chapters in books typically include:

• name of author(s)
• title of the chapter
• name of book's editor
• name of book and other details as above
• chapter number or page numbers for the chapter (optional)

In some instances, the verso of a book's title page may record, "Reprinted with corrections XXXX" or similar, where "XXXX" is a year. This is a different version of a book in the same way that different editions are different versions. Note this in your citation. See § Dates and reprints for how to further information.

Journal articles

Citations for journal articles typically include:

• name of the author(s)
• year and sometimes month of publication
• title of the article
• name of the journal
• volume number, issue number, and page numbers (article numbers in some electronic journals)
• DOI and/or other identifiers are optional and can often be used in place of a less stable URL (although URLs may also be listed in a journal citation)

Newspaper articles

Citations for newspaper articles typically include:

• byline (author's name), if any
• title of the article
• name of the newspaper in italics
• city of publication (if not included in name of newspaper)
• date of publication
• page number(s) are optional and may be substituted with negative number(s) on microfilm reels

Web pages

Citations for World Wide Web pages typically include:

• URL of the specific web page where the referenced content can be found
• name of the author(s)
• title of the article
• title or domain name of the website
• publisher, if known
• date of publication
• page number(s) (if applicable)
• the date you retrieved (or accessed) the web page (required if the publication date is unknown)

Sound recordings

Citations for sound recordings typically include:

• name of the composer(s), songwriter(s), script writer(s) or the like
• name of the performer(s)
• title of the song or individual track
• title of the album (if applicable)
• name of the record label
• year of release
• medium (for example: LP, audio cassette, CD, MP3 file)
• approximate time at which event or point of interest occurs, where appropriate

Do not cite an entire body of work by one performer. Instead, make one citation for each work your text relies on.

Film, television, or video recordings

Citations for films, TV episodes, or video recordings typically include:

• name of the director
• name of the producer, if relevant
• names of major performers
• the title of a TV episode
• title of the film or TV series
• name of the studio
• year of release
• medium (for example: film, videocassette, DVD)
• approximate time at which event or point of interest occurs, where appropriate

Wikidata

Wikidata is largely user-generated, and articles should not directly cite Wikidata as a source (just as it would be inappropriate to cite other Wikipedias' articles as sources).

But Wikidata's statements can be directly transcluded into articles; this is usually done to provide external links or infobox data. For example, more than two million external links from Wikidata are shown through the {{Authority control}} template. There has been controversy over the use of Wikidata in the English Wikipedia due to vandalism and its own sourcing. While there is no consensus on whether information from Wikidata should be used at all, there is general agreement that any Wikidata statements that are transcluded need to be just as – or more – reliable compared to Wikipedia content. As such, Module:WikidataIB and some related modules and templates filter Wikidata statements not supported by a reference by default; however, other modules and templates, such as Module:Wikidata, do not.

To transclude an item from Wikidata, the QID (Q number) of an item in Wikidata needs to be known. QID can by found by searching for an item by the name or DOI in Wikidata. A book, a journal article, a musical recording, sheet music or any other item can be represented by a structured item in Wikidata.

The {{Cite Q}} template can be used to cite works whose metadata is held in Wikidata, provided the cited work meets Wikipedia's standards. As of December 2020, {{Cite Q}} does not support "last, first" or Vancouver-style author name lists, so it should not be used in articles in which "last, first" or Vancouver-style author names are the dominant citation style.

Other

See also:

• {{cite album notes}}
• {{cite comic}}
• {{cite conference}} for conference reports or papers
• {{cite court}} for court cases or legal decisions
• {{cite act}} for a law or legal act
• {{cite encyclopedia}}
• {{cite episode}} for TV or radio series
• {{cite mailing list}}
• {{cite map}}
• {{cite newsgroup}}
• {{cite patent}} for patents
• {{cite press release}}
• {{cite report}}
• {{cite thesis}}
• {{cite video game}}