A citation in a Wikipedia article is a piece of text that uniquely identifies a reliable source for certain information in that article, for example: "Ritter, Ron. The Oxford Style Manual. Oxford University Press, 2002, p. 1." Citations are usually given as footnotes, although occasionally they are placed within the body of the article.
When to cite sources: The policy on sourcing, Verifiability, requires inline citations for any material challenged or likely to be challenged, and for all quotations. This applies to all material in article space—including article content, lists, and image captions—without exception. However, editors are also encouraged to provide citations for all information added to Wikipedia.
How to write citations: This page contains information on how to place and format citations. Each article should use the same citation method throughout. If an article already has citations, adopt the method in use or seek consensus on the talk page before changing it. 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.
Wikipedia guidelines
Behavioral
Assume good faith Conflict of interest Don't bite the newbies Don't disrupt Wikipedia to make a point Etiquette Gaming the system User pages
Source means the piece of work which supports the information given in Wikipedia. For information on what kind of sources are considered reliable for this purpose, see Wikipedia:Verifiability#Reliable sources.
A citation is a line of text that identifies a source; for example, Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 1.
An inline citation is a citation, usually in the form of a footnote, added close to the material it supports—for example after the sentence or paragraph.
Reference may refer to the citation or to the source.
How to format and place citations
ଇନଲାଇନ ଆଧାର
WP:INCITE
An inline citation is a line of text—such as <ref>Smith, John. ''Name of Book''. Oxford University Press, 2011, p. 1</ref>—that identifies a source; it is 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 sentence or paragraph, so long as it's clear which source supports which part of the text.
Two styles of inline citation are commonly used on Wikipedia: clickable footnotes (<ref> tags, as above) and parenthetical references. The latter would involve adding (Smith 2011, p. 1) in round brackets within the sentence, while the former would include the same citation in a footnote.
A quick how-to
Most editors add inline citations inside footnotes; see below for more details. One easy way to write them is to add a citation like this to the end of the relevant phrase, sentence, or paragraph:
<ref>Rawls, John. ''A Theory of Justice''. Harvard University Press, 1971, p. 1.</ref>
<ref>Sanger, David E. [http://www.nytimes.com/2010/09/24/world/24prexy.html?_r=1&hp "With Warning, Obama Presses China on Currency"], ''The New York Times'', September 23, 2010, accessed October 31, 2010.</ref>
Then add this to the end of the article:
==Notes==
{{reflist}}
Footnotes and References
WP:CITEFOOT
"Footnote" and "note" are used interchangeably to refer to citations and commentary placed between ref tags, so that they appear at the end of the article under a Notes or References section heading; the term "endnote" is not used on Wikipedia.
Most Wikipedia articles place their citations in footnotes. These appear as clickable numbers within the text, which link to a numbered list of full citations at the end of the article. The citations will appear at the end of the article if you type {{Reflist}}.[୧] This will generate the list of footnotes. This is usually called the Notes or References section.
For a citation to appear in a footnote, it must be enclosed within "ref" tags. You can add these by typing <ref> at the front of the citation and </ref> at the end. Alternatively use the list of "markup" in the edit box, which includes <ref></ref>.
This is how it looks in the edit box:
The Sun is pretty big,<ref>Miller, Edward. ''The Sun''. Academic Press, 2005, p. 1.</ref> but the Moon is not so big.<ref>Brown, Rebecca. "Size of the Moon," ''Scientific American'', 51(78):46.</ref> The Sun is also quite hot.<ref>Smith, John. ''The Sun's Heat''. Academic Press, 2005, p. 2.</ref>
==Notes== {{Reflist}}
This is how it looks in the article:
The Sun is pretty big,[1] but the Moon is not so big.[2] The Sun is also quite hot.[3]
Notes
For multiple citations of the same reference or footnote, you can also use the name attribute by using <ref name=name>details of the citation</ref>. Thereafter, the same footnote may be used multiple times by adding <ref name=name/>. If the name contains an embedded blank space, you must either add straight quotation marks (<ref name="name more"/>) or replace the unacceptable blank space with an acceptable symbol such as an underscore or a hyphen (e.g., <ref name=name_more/> or <ref name=name-more/>), thus eliminating the need for quotation marks. The name is case-sensitive, but quoted names match names without quotes; USGS is matched by "USGS" but not by usgs.
Shortened footnotes
WP:CITESHORT
WP:SFN
Many articles use short citations in footnotes, giving the author, year, and page number, such as <ref>Smith 2010, p. 1.</ref> As before, the list of footnotes is automatically generated in a "Notes" or "Footnotes" section. A full citation is then added in a "References" section. Short citations can be written manually, or by using the {{sfn}} or {{harvnb}} templates. (Note that templates should not be added without consensus to an article that already uses a consistent referencing style.) The short and full citations may be linked so that the reader can click on the short note to highlight the full citation. 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:
The Sun is pretty big,[1] but the Moon is not so big.[2] The Sun is also quite hot.[3]
Notes
References
Brown, Rebecca (2006). "Size of the Moon", Scientific American, 51(78).
Miller, Edward (2005). The Sun. Academic Press.
Shortened notes using titles rather than publication dates would look like this in the article:
Notes
Since the links are placed manually it is easy to introduce errors such as duplicate anchors and unused references. The script User:Ucucha/HarvErrors will show many related errors. Duplicate anchors may be found by using the W3C Markup Validation Service.
List-defined references
As of September 2009, the Cite.php extension was modified to support list-defined references. These can be implemented with the |refs= parameter to the {{Reflist}} template, or by using a pair of HTML tags (<references> and </references>) in place of the <references /> tag. These reduce clutter within articles, by putting all the citation details in the section at the end where the footnotes are displayed. Defined references must be used within the body; unused references will show an error message. Non-list-defined references (ordinary footnote references enclosed with <ref> and </ref> tags) will display as normal along with list-defined ones. As with other citation formats, list-defined references should not be added to articles that already have a stable referencing system, unless there is consensus to do so. When in doubt, follow the referencing system used by the first major contributor to employ a consistent style.
This is how it looks in the edit box:
The Sun is pretty big,<ref name="Miller2005p23" /> but the Moon is not so big.<ref name="Brown2006" /> The Sun is also quite hot.<ref name="Miller2005p34" />
==References== {{Reflist|refs= <ref name="Miller2005p23">Miller, Edward.''The Sun''. Academic Press, 2005, p. 23.</ref> <ref name="Miller2005p34">Miller, Edward.''The Sun''. Academic Press, 2005, p. 34.</ref> <ref name="Brown2006">Brown, Rebecca. "Size of the Moon," ''Scientific American,'' 51(78):46</ref> }}
This is how it looks in the article:
The Sun is pretty big,[1] but the Moon is not so big.[2] The Sun is also quite hot.[3]
References
Parenthetical referencing
In parenthetical referencing, a short citation, such as (Smith 2010, p. 1), is added in parentheses (round brackets) just after the point it is supporting. Several forms of parenthetical referencing are used in Wikipedia, including author-date referencing (APA style, Harvard style, or Chicago style), and author-title or author-page referencing (MLA style or Chicago style). The full citation (Smith, John. Name of Book. Cambridge University Press, 2010) is then added in alphabetical order, according to the authors' surnames, at the end of the article in a "References" section. The inline and full citation may be linked using a template (see linking inline and full citations); as with other citation templates, these should not be added to articles without consensus.
This is how it looks in the edit box:
The Sun is pretty big (Miller 2005, p. 1), but the Moon is not so big (Brown 2006, p. 2). The Sun is also quite hot (Miller 2005, p. 3). == References == *Brown, R (2006). "Size of the Moon", ''Scientific American'', 51(78). *Miller, E (2005). ''The Sun'', Academic Press.
This is how it looks in the article:
The Sun is pretty big (Miller 2005, p. 1), but the Moon is not so big (Brown 2006, p. 2). The Sun is also quite hot (Miller 2005, p. 3).
References
Brown, R (2006). "Size of the Moon", Scientific American, 51(78).
Miller, E (2005). The Sun, Academic Press.
Text-source integrity
WP:INTEGRITY
When using inline citations, it is important to maintain text-source integrity. The point of an inline citation is to allow readers and other editors to check that the material is sourced; that point is lost if the citation is not clearly placed. The distance between material and its source is a matter of editorial judgment, but adding text without placing its source clearly can lead to allegations of original research, violations of the sourcing policy, and even plagiarism. Editors should exercise caution when rearranging or inserting material to ensure that text-source relationships are maintained.
The following inline citation, for example, is not helpful, because the reader does not know whether each source supports the material; each source supports part of it; or just one source supports it with the others added as further reading:
N Delia Smith is the UK's best-selling cookery writer.[୨][୩][୪][୫]
Where you are using multiple sources for one sentence, consider bundling citations at the end of the sentence or paragraph with an explanation in the footnote regarding which source supports which point; see below for how to do that.
You can combine or "bundle" citations between one set of ref tags at the end of a sentence or paragraph, along with an explanation in the footnote for which source supports which part of the text. Citation bundling can be done with long or short footnotes, with or without citation templates. It has multiple benefits:
it helps readers and other editors see at a glance which source supports which point, maintaining text-source integrity;
it avoids the visual clutter of multiple clickable footnotes inside a sentence or paragraph;
it avoids the confusion of having multiple sources listed separately after sentences, with no indication of which source to check for each part of the text, such as this.[୬][୭][୮][୯]
it makes it less likely that inline citations will be moved inadvertently when text is re-arranged, because the footnote states clearly which source supports which point.
A simple example of citation bundling:
The sun is pretty big, but the moon is not so big. The sun is also quite hot.[1]
Notes
In-text attribution
WP:INTEXT
In-text attribution is the attribution inside a sentence of material to its source, in addition to an inline citation after the sentence. In-text attribution should be used with direct speech (a source's words between quotation marks); indirect speech (a source's words without quotation marks); and close paraphrasing. It can also be used when loosely summarizing a source's position in your own words. It avoids inadvertent plagiarism, and helps the reader see where a position is coming from. An inline citation should follow the attribution, usually at the end of the sentence or paragraph in question.
For example:
Y John Rawls argues that, to reach fair decisions, parties must consider matters as if behind a veil of ignorance.[୧୦]
When using in-text attribution, make sure it doesn't lead to an inadvertent neutrality violation. For example, the following implies parity between the sources, without making clear that the position of Dawkins is the majority view:
N Richard Dawkins argues that human beings evolved through natural selection, but John Smith writes that we arrived here in pods from Mars.
Neutrality issues apart, there are other ways in-text attribution can mislead. The sentence below suggests The New York Times has alone made this important discovery:
N According to The New York Times, the sun will set in the west this evening.
Simple facts such as this can have inline citations to reliable sources as an aid to the reader, but normally the text itself is best left as a plain statement without in-text attribution:
YBy mass, oxygen is the third most abundant element in the universe after hydrogen and helium.[୧୧]
Dealing with unsourced material
WP:NOCITE
If an article is unreferenced you can tag it with the template {{Unreferenced}}, so long as it is not nonsensical or a biography of a living person, in which case request admin assistance.
If a claim is doubtful but not harmful, use the {{fact}} tag, which will add "citation needed," but remember to go back and remove the claim if no source is produced within a reasonable time.
If a claim is doubtful and harmful, remove it from the article. You may want to move it to the talk page and ask for a source, unless it is very harmful or absurd, in which case it should not be posted to the talk page either. Use your common sense.
Don't cite a source unless you've seen it for yourself. Where you want to cite John Smith, but you've only read Paul Jones who cites Smith, write it like this (this formatting is just an example; there are several ways this can be written):
Smith, John. Name of Book I Haven't Seen, Cambridge University Press, 2009, p. 1, cited in Paul Jones (ed.). Name of Encyclopedia I Have Seen. Oxford University Press, 2010, p. 2.
If you first learned of John Smith's book because it was cited in Paul Jones' encyclopedia, but you then actually obtained and read John Smith's book, it is not necessary to give "credit" to any sources, search engines, websites, library catalogs, etc., that led you to Smith's book. You may cite Smith's book directly and solely in that instance.
For a source available in hardcopy, microform, and/or online, omit, in most cases, which one you read. While it is useful to cite author, title, edition (1st, 2d, etc.), and similar information, it generally is not important to cite a database such as ProQuest, EbscoHost, or JStor (see the list of academic databases and search engines) or to link to such a database requiring a subscription or a third party's login. The basic bibliographic information you provide should be enough to search for the source in any of these databases that have the source. Don't add a URL that has a part of a password embedded in the URL. However, you may provide the DOI, ISBN, or another uniform identifier, if available. If the publisher offers a link to the source or its abstract that does not require a payment or a third party's login for access, you may provide the URL for that link. And if the source exists only online, give the link even if access is restricted.
Multimedia
Multimedia material should be referenced just like article text. Citations for a media file should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. If an infobox or table contains text that needs citing, but the box or table cannot incorporate an inline citation, the citation should appear in a caption or other text that discusses the material. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself. Material that identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg) is considered attribution and normally does not need further citation.
Avoid scrolling lists
WP:ASL
Scrolling lists, or lists of citations appearing within a scroll box, should never be used because of issues with readability, accessibility, printing, and site mirroring. Additionally, it cannot be guaranteed that such lists will display properly in all web browsers. See this July 2007 discussion for more detail.
General reference
A general reference is a citation to a reliable source that supports content, but is not displayed as an inline citation. General references are usually listed at the end of the article in a References section. They may be found in underdeveloped articles, especially when all article content is supported by a single source. The disadvantage of using general references is that text-source integrity is lost, unless the article is very short. The sourcing policy, Verifiability, requires inline citations for all quotations, and for anything challenged or likely to be challenged.
A general reference looks like this in the edit box:
The Sun is pretty big, but the Moon is not so big. The Sun is also quite hot.
== References == *Brown, R (2006). "Size of the Moon", ''Scientific American'', 51(78). *Miller, E (2005). ''The Sun'', Academic Press.
This is how it looks in the article:
The Sun is pretty big, but the Moon is not so big. The Sun is also quite hot.
References
Brown, R (2006). "Size of the Moon", Scientific American, 51(78).
Miller, E (2005). The Sun, Academic Press.
Embedded links
Embedded links to external websites should not be used as a form of inline citation, because they are highly susceptible to linkrot. Wikipedia allowed this in its early years—for example by adding a link after a sentence, like this [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html], which looks like this. [୧] This is no longer recommended. Raw links are not recommended in lieu of properly written out citations, even if placed between ref tags, like this <ref>[http://media.guardian.co.uk/site/story/0,14173,1601858,00.html]</ref>.
Embedded links should never be used to place external links in the body of an article, like this: "Apple, Inc. announced their latest product..."
Further reading/External links
"Further reading" or "External links" are used as section headings for books, articles, and websites related to the topic that have not been used as sources.
Citation style
There are a number of citation styles. See here for some examples. They all include the same information, but vary in punctuation and the order of the author's name, publication date, title, and page numbers.
Although nearly any consistent style may be used, avoid all-numeric date formats other than YYYY-MM-DD, because of the ambiguity concerning which number is the month and which the day. If used, YYYY-MM-DD format should be limited to Gregorian calendar dates where the year is after 1582.
Style variation and consistency
WP:CITEVAR
Citations within each Wikipedia article should follow a consistent style. Editors may choose any style they want. The English Wikipedia does not have a house style, so it need not match what is done in other articles.
If the article you are editing is already using a particular citation style, you should follow it. Do not change it merely for personal preference or cosmetic reasons. If you think the existing citation system is inappropriate for the needs of the article, seek consensus for a change on the talk page. As with issues of spelling differences, if there is disagreement about which style is best, defer to the style used by the first major contributor. If you are the first major contributor to an article, you may choose whichever style you think best for the article.
To be avoided
Switching between major citation styles, e.g., switching between parenthetical and <ref> tags or between the style preferred by one academic discipline vs. another;
Adding citation templates to an article that already uses one of the other citation formats listed in this guideline;
Changing the section heading to or from ==References==, ==Notes==, etc.
Generally considered helpful
Replacing bare URLs with full bibliographic citations: an improvement because it provides more information to the reader and fights linkrot;
Replacing some or all general references with inline citations: an improvement because it provides more information to the reader and helps maintain text-source integrity;
Imposing one style on an article with incompatible citation styles (e.g., where some of the citations are in footnotes and others are parenthetical references): an improvement because it makes the formatting consistent.
Citations for individually authored chapters in books typically include:
name of author
the title of the chapter
name of the book's editor
name of book and other details as above
the chapter number or page numbers for the chapter are optional
Journal articles
Citations for journal articles typically include:
name of the author(s)
year and sometimes month of publication
title of the article within quotation marks
name of the journal in italics
volume number, issue number, and page numbers (article numbers in some electronic journals)
DOI and/or other identifiers where available
Newspaper articles
Citations for newspaper articles typically include:
name of the newspaper in italics
date of publication
byline (author's name), if any
title of the article within quotation marks
city of publication, if not included in name of newspaper
page number(s) are optional
Webpages
Citations for World Wide Web pages typically include:
name of the author(s)
title of the article within quotation marks
name of the website
date of publication
page number(s) (if applicable)
the date you retrieved it (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)
name of the performer(s)
title of the song or individual track in quotation marks
title of the album in italics (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
Film, TV, 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
for a TV episode, the title of the episode in quotation marks
title of the film or TV series in italics
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
Identifying parts of a source
WP:Page numbers
When citing lengthy sources, you should identify which part of a source is being cited.
Books and print articles
Specify the page number or range of page numbers. Page numbers are not required for a reference to the book or article as a whole. When you specify a page number, it is helpful to specify the version (date and edition for books) of the source because the pagination can change between editions.
Audio and video sources
Specify the time at which the event or other point of interest occurs. Be as precise as possible about the version of the source that you are citing; for example, movies are often released in different editions or "cuts". Due to variations between formats and playback equipment, precision may not be accurate in some cases. However, many government agencies do not publish minutes and transcripts but do post video of official meetings online; generally the subcontractors who handle audio-visual are quite precise.
Links and ID numbers
A citation ideally includes a link or ID number to help editors locate the source. If you have a URL (webpage) link, you can add it to the title part of the citation, so that when you add the citation to Wikipedia the URL becomes hidden and the title becomes clickable. To do this, enclose the URL and the title in square brackets—the URL first, then a space, then the title. For example:
Carr A, Ory D (2006). [http://dx.doi.org/10.1371/journal.pmed.0030496 Does HIV cause cardiovascular disease?] ''PLoS Medicine'', 3(11):e496.
For web-only sources with no publication date you should include a "Retrieved" date instead, in case the webpage changes in the future. For example: Retrieved 2008-07-15.
You can also add an ID number to the end of a citation. The ID number might be an ISBN for a book, a DOI (Digital Object Identifier) for an article, or any of several ID numbers that are specific to particular article databases, such as a PMID number for articles on PubMed. It may be possible to format these so that they are automatically activated and become clickable when added to Wikipedia, for example by typing ISBN (or PMID) following by a space followed by the ID number.
If your source is not available online, it should be available in reputable libraries, archives, or collections. If a citation without an external link is challenged as unavailable, any of the following is sufficient to show the material to be reasonably available (though not necessarily reliable): providing an ISBN or OCLC number; linking to an established Wikipedia article about the source (the work, its author, or its publisher); or directly quoting the material on the talk page, briefly and in context.
Linking to Google Books pages
WP:PAGELINK
WP:PAGELINKS
Google Books allows book pages to be linked to directly, where the book is available for preview. These can be written in a number of ways, with or without citation templates:
In edit mode, the URL for p. 18 of A Theory of Justice looks like this:
Rawls, John. [http://books.google.com/books?id=kvpby7HtAe0C&pg=PA18 ''A Theory of Justice'']. Harvard University Press, 1971, p. 18.
When the page number is a Roman numeral, commonly seen at the beginning of books, the URL looks like this:
http://books.google.com/books?id=kvpby7HtAe0C&pg=PR17—for page xvii of the same book.
Page links should only be added when the book is available for preview; they will not work with snippet view. No editor is required to add page links, but if another editor adds them, they should not be removed; see the October 2010 RfC for further information.
Convenience links
A convenience link is a link to a copy of your source on a webpage provided by someone other than the original publisher or author. For example, a copy of a newspaper article no longer available on the newspaper's website may be hosted elsewhere. When offering convenience links, it is important to be reasonably certain that the convenience copy is a true copy of the original, without any changes or inappropriate commentary, and that it does not infringe the original publisher's copyright. Accuracy can be assumed when the hosting website appears reliable. Where several sites host a copy of the material, the site selected as the convenience link should be the one whose general content appears most in line with Wikipedia:Neutral point of view and Wikipedia:Verifiability.
Citation templates and tools
WP:CITECONSENSUS
For a comparison of citations using templates with citations written freehand, see Wikipedia:Citing sources/Example edits for different methods.
Citation templates are used to format citations in a consistent way. The use of citation templates is neither encouraged nor discouraged. Templates may be used or removed at the discretion of individual editors, subject to agreement with other editors on the article. Because templates can be contentious, editors should not change an article with a distinctive citation format to another without gaining consensus. Where no agreement can be reached, defer to the style used by the first major contributor.
Metadata
Citations may be accompanied by metadata, though it is not mandatory. Most citation templates on Wikipedia use the COinS standard. Metadata such as this allow browser plugins and other automated software to make citation data accessible to the user, for instance by providing links to their library's online copies of the cited works. In articles that format citations manually, metadata may be added manually in a span, according to the COinS specification; or the templates Template:Citation metadata or Template:COinS can be used.
User:Citation bot (formerly DOI bot) – a bot that automatically fixes common errors in individual citations, and adds missing fields
User:CitationTool – a tool for finding article-level citation errors and fixing them. Not currently functional.
Reflinks adds titles to bare references and other cleanup
Programming tools
Wikicite is a free program that helps editors to create citations for their Wikipedia contributions using citation templates. It is written in Visual Basic .NET, making it suitable only for users with the .NET Framework installed on Windows, or, for other platforms, the Mono alternative framework. Wikicite and its source code is freely available; see the developer's page for further details.
Wikicite+ is a program based on the original Wikicite source code. It features extra validation, bug fixes, additional cite templates (such as cite episode) as well as tools for stub sorting and more. It is also available for free under the Apache License 2.0 and is open source.
User:Richiez has tools to automatically handle citations for a whole article at a time. Converts occurrences of {{pmid XXXX}} or {{isbn XXXX}} to properly formatted footnote or Harvard-style references. Written in ruby and requires a working installation with basic libraries.
pubmed2wiki.xsl an XSL stylesheet transforming the XML output of PubMed to Wikipedia refs.
RefTag by Apoc2400 creates a prefilled {{cite book}} template with various options from a Google Books URL. The page provides a bookmarklet for single-click transfer.
wikiciter web interface, does google books, pdf files, beta.
Citation export tools
You can insert a link beside each citation in Wikipedia, allowing you to export the citation to a reference manager, such as EndNote. Just copy this code:
To help prevent dead links, persistent identifiers are available for some sources. Some journal articles have a digital object identifier (DOI); some online newspapers and blogs, and also Wikipedia, have permalinks that are stable. When permanent links aren't available, consider archiving the referenced document when writing the article; on-demand web archiving services such as WebCite (http://www.webcitation.org) are fairly easy to use (see pre-emptive archiving).
Dead links should be repaired or replaced if possible. Do not delete a citation merely because the URL is not working today. Follow these steps when you encounter a dead URL being used as a reliable source to support article content:
Confirm status: First, check the link to confirm that it is dead and not temporarily down. Search the website to see whether it has been rearranged.
Check for web archives: Several archive services exist; add one of these URLs if available:
The Internet Archive and WebCite have billions of archived webpages. See Wikipedia:Using the Wayback Machine and Wikipedia:Using WebCite.
Note: Most archives currently operate with a delay of ~18 months before a link is made public. As a result, editors should wait ~24 months after the link is first tagged as dead before declaring that no web archive exists. Dead URLs to reliable sources should normally be tagged with {{dead link|date=ଅପ୍ରେଲ ୨୦୨୪}}, so that you can estimate how long the link has been dead.
Remove convenience links: If the material was published on paper (e.g., academic journal, newspaper article, magazine, book), then the URL is not necessary. Simply remove it.
Find a replacement source: Search the web for quoted text or the article title. Consider contacting the website/person that originally published the reference and asking them to republish it. Ask other editors for help finding the reference somewhere else. Find a different source that says essentially the same thing as the reference in question.
Remove hopelessly lost web-only sources: If the source material does not exist offline, and if there is no archived version of the webpage (be sure to wait ~24 months), and if you are unable to find another copy of the material, then the dead citation should be removed and the material it supports should be regarded as unverifiable. If it is material that is specifically required by policy to have an inline citation, then please consider tagging it with {{citation needed}}. It may be helpful to future editors if you move the citation to the talk page with an explanation.
Wikipedia:Verification methods – listing examples of the most common ways that citations are used in Wikipedia articles.
Wikipedia:Citing sources/example style – listing examples of full citations using APA and Harvard referencing techniques.
Wikipedia:Citing sources/Example edits for different methods – showing comparative edit mode representations for different citation methods and techniques.
Wikipedia:Citing sources/Further considerations – information of additional interest.
