Help:Citation Style 1

Citation Style 1 (CS1) is a collection of reference citation templates that can be modified to create different styles for different referenced materials. Its purpose is to provide a set of default formats for references on Wikipedia. It includes a series of templates that in turn use Module:Citation/CS1.

Wikipedia does not have a single house style. Editors may choose any option they want; one article need not match what is done in other articles or what is done in professional publications or recommended by academic style guides. However, citations within a given article should follow a consistent style.

If the article you are editing is already using a particular citation style, you should follow it; if you believe it is inappropriate for the needs of the article, seek consensus for a change on the talk page.

CS1 uses (in addition to Wikipedia's own Manual of Style) elements of The Chicago Manual of Style and the , with significant adaptations.

There are a number of templates that use a name starting with cite; many were developed independently of CS1 and are not compliant with the CS1 style. There are also a number of templates that use one of the general use templates as a meta-template to cite a specific source.

The following is a list of templates that implement Citation Style 1 for one or more types of citations but are not restricted to any specific source.

There are a number of templates that are CS1 compliant, because they use a CS1 template as a base, but are tied to a specific source; these are listed in .

This help page uses the names most commonly used across the templates series; see each template's documentation for details.

(where "n.d." could also be any other valid date formatted per the MOS)

An author may be cited using separate parameters for the author's surname and given name by using |last= and |first= respectively. If a cited source has multiple authors, subsequent authors can be listed in the citation using |last2= and |first2=, |last3= and |first3=, etc.[Note 1] For symmetry with the other numbered parameters, |last1= and |first1= are available as well, as shown in the following example:

For symmetry with similar parameters for editors and other contributors (discussed further below), longer parameter forms are also available for authors: |author-last= and |author-first=, as well as numbered variants like |author-lastn= and |author-firstn= or |authorn-last= and |authorn-first= (with n referring to this author's number in the list). Because the shorthand parameters might erroneously have been used also for editors and other types of contributors by some Wikipedians in the past, please make sure that the parameters actually refer to authors when expanding |last= and |first= parameters to their longer equivalents (equivalent parameters for editors etc. exist as well, see below).

If a cited source has a large number of authors, one can limit the number of authors displayed when the citation is published by using the |display-authors= parameter as described in detail in the Display options section of this help page.

If a cited author is notable and the author has a Wikipedia article, the author's name can be linked with |author-link=.[Note 2] If a citation includes multiple notable authors, one may use |author-linkn= or |authorn-link=, etc. This method is used because the |last=- and |first=-type parameters do not allow wikilinking. However, |author-link= cannot be used to link to an external website; the external link will not render correctly.[Note 2] Below is an example of a wikilinked author credit:

When an author is cited, the date of the cited work is displayed after the author's name, as shown in the example below:

If no author is cited, the date appears after the title, as shown in the example below:

If the cited source does not credit an author, as is common with newswire reports, press releases or company websites use:

This HTML comment alerts fact-checking and citation-fixing editors, and potentially bots, that the cited source did not name an author—the author was not overlooked. Without this entry editors and bots would waste time researching cited sources for a non-existent author credit.

Editors should use an |author= organizational citation when the cited source, such as a committee report, specifically names an official body or a sub-unit of the publisher as the collective author of the work, e.g. |author=Commission on Headphone Safety or |author=Rules Sub-committee. Do not use |author= to assert what you think was probably the collective author when the source itself does not specifically specify a collective author; doing so is original research and falsification of source verifiability and reliability.

|author= should never hold the name of more than one author. Separate individual authors into enumerated individual |authorn= parameters.

An editor may be cited using separate parameters for the editor's last and first name. A single or first editor would use |editor-last= and |editor-first=; subsequent editors would use |editor2-last= and |editor2-first=, |editor3-last= and |editor3-first=, etc.

If an editor has a Wikipedia article, you may wikilink to that Wikipedia article using |editor-link=.[Note 2] If a cited work has multiple editors, you may use |editor2-link=, |editor3-link=, etc. to wikilink to each editor's Wikipedia article. This method is used because |editor-last= and |editor-first= do not allow wikilinking. |editor-link= cannot be used to link to an external website.

If a cited source has a large number of editors, one can limit the number of editors displayed when the citation is published using the |display-editors= parameter as described in detail in the Display options section of this help page.

A translator may be cited using separate parameters for the translator's last and first name. A single or first translator would use |translator-last= and |translator-first=; subsequent translators would use |translator2-last= and |translator2-first=, |translator3-last= and |translator3-first=, etc.

If a translator has a Wikipedia article, you may wikilink to that Wikipedia article using |translator-link=.[Note 2] If a cited work has multiple translators, you may use |translator2-link=, |translator3-link=, etc. to wikilink to each translator's Wikipedia article. This method is used because |translator-last= and |translator-first= do not allow wikilinking. |translator-link= cannot be used to link to an external website.

When a source does not have a publication date, use |date=n.d. or |date=nd

Acceptable date formats are shown in the "Acceptable date formats" table of the . Further points:

CS1 uses (MOS:DATEFORMAT) as the reference for all date format checking performed by Module:Citation/CS1. For various reasons, CS1 is not fully compliant with MOS:DATEFORMAT. This table indicates CS1 compliance with the listed sections of MOS:DATEFORMAT.

If dates are used, the year range is 100 to present without era indication (AD, BC, CE, BCE). In the case where the same author has written more than one work in the same year, a lower-case letter may be appended to the year in the date parameter (|date=July 4, 1997b) or the year parameter (|year=1997b).

Example: to have the CS1/CS2 templates in an article render their publication dates in the long form (fully spelled-out month names) with access-/archive-dates rendered in short form (abbreviated month names), write:

This global setting may be overridden in individual CS1/CS2 templates by use of |df=; abbreviated date forms are not supported by |df=.

Titles containing certain characters will both display and link incorrectly unless those characters are replaced or encoded like this:

Language codes known to cs1|2 for languages that do not use a Latin script are:

An editor may use any one of the following parameters in a given citation to refer to the specific page(s) or place in a cited source that contains the information that supports the article text. If more than one of the following parameters are used in the same citation, the error message Extra |pages= or |at= (help) will display in the published citation. When more than one of the following parameters is used in error, |page= overrides both |pages= and |at=; |pages= overrides |at=. To resolve the error, remove extra parameters of this type until only one remains in the affected citation.

When MediaWiki encounters an external link URL with a '.pdf' or '.PDF' extension, it renders the external link with a in place of the usual . To make rendered cs1|2 citations that link to PDF documents somewhat more accessible, cs1|2 automatically adds a parenthetical PDF annotation so that those readers using screen-reader technology can know the type of the linked file. This is imperfect because some on-line sources redirect .pdf URLs to .html landing pages (this is common for PDF documents behind paywalls or registration barriers). Because the parenthetical PDF annotation happens automatically, editors are not required to set |format=PDF, though doing so causes no harm. The |format=PDF parameter may be deleted as part of a more substantial edit but editors should consider that many cs1|2 templates are copied from en.Wikipedia to other-language Wikipedias when articles here are translated to that other language. Do not assume that other-language Wikipedias use up-to-date cs1|2 templates; many do not so removing |format=PDF here can affect readers/translators at other Wikipedias.

Links to sources are regarded as conveniences and are not required, except when citing Web-only sources. There are many digital libraries with works that may be used as sources.

Links should be kept as simple as possible. For example, when performing a search for a Google Book, the link for Monty Python and Philosophy would look like:

A direct link to a specific page may be used if supported by the host. For example, the link to page 172 of Monty Python and Philosophy on Google Books:

URLs must begin with a supported URI scheme. http:// and https:// will be supported by all browsers; however, ftp://, gopher://, irc://, ircs://, mailto: and news: may require a plug-in or an external application and should normally be avoided. IPv6 host-names are currently not supported.

If URLs in citation template parameters contain certain characters, then they will not display and link correctly. Those characters need to be percent-encoded. For example, a space must be replaced by %20. To encode the URL, replace the following characters with:

Single apostrophes do not need to be encoded; however, unencoded multiples will be parsed as italic or bold markup. Single curly closing braces also do not need to be encoded; however, an unencoded pair will be parsed as the double closing braces for the template transclusion.

The original link may become unavailable. When an archived version is located, the original URL is retained and |archive-url= is added with a link to an archived copy of a web page, usually from services like WebCite and the Internet Archive. |archive-date= must be added to show the date the page was archived, not the date the link was added. When |archive-url= is used, |url= and |archive-date= are required, else an error will show. When an archived link is used, the citation displays with the title linked to the archive and the original link at the end: . Archived from on 2013-05-01.

When the original URL has been usurped for the purposes of spam, advertising, or is otherwise unsuitable, setting |url-status=unfit or |url-status=usurped suppresses display of the original URL (but |url= and |archive-url= are still required).

The following identifiers create links and are designed to accept a single value. Using multiple values or other text will break the link and/or invalidate the identifier. In general, the parameters should include only the variable part of the identifier, e.g. |rfc=822 or |pmc=345678.

In very rare cases, valid identifiers (f.e., as actually printed on publications) do not follow their defined standard format or use non-conforming checksums, which would typically cause an error message to be shown. Do not alter them to match a different checksum. In order to suppress the error message, some identifiers (|doi=, |eissn=, |isbn=, |issn=, and |sbn=) support a special accept-this-as-written markup which can be applied to disable the error-checking (as |<param>=((<value>))). If the problem is down to a mere typographical error in a third-party source, correct the identifier value instead of overriding the error message.

For some identifiers, it is possible to specify the access status using the corresponding |<param>-access= parameter.

It is not necessary to specify a URL to a link identical to a link also produced by an identifier. The |url= parameter (or |title-link=) can then be used for providing a direct deep link to the corresponding document or a convenience link to a resource that would not otherwise be obviously accessible.

Citations of online sources that require registration or a subscription are acceptable in Wikipedia as documented in Verifiability § Access to sources. As a courtesy to readers and other editors, editors should signal restrictions on access to material provided via the external links included in a citation. These levels describe requirements or constraints related to accessing and viewing the cited material; they are not intended to indicate the ability to reuse, or the copyright status, of the material, since that status is not relevant to verifying claims in articles.

As there are often multiple external links with different access levels in the same citation, each value is attributed to a specific external link.

Online sources linked by |url=, |article-url=, |chapter-url=, |contribution-url=, |entry-url=, |map-url=, and |section-url= are presumed to be free-to-read. When they are not free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. Because the sources linked by these url-holding parameters are presumed to be free-to-read, they may not be marked as free.

For example, this cites a web page that requires registration but not subscription:

Links inserted by named identifiers are presumed to lie behind a paywall or registration barrier – exceptions listed below. When they are free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. When the sources linked by these named-identifier parameters are not presumed to carry a free-to-read full text (for instance because they're just abstracting services), they may not be marked as limited, registration, or subscription.

Some named-identifiers are always free-to-read. For those named identifiers there are no access-indicator parameters; the access level is automatically indicated by the template. These named identifiers are:

For embargoed pmc that will become available in the future, see pmc-embargo-date.

The module creates HTML IDs by default suitable for use with shortened footnotes using the Harv- and sfn-family templates. These styles use in-text cites with a link that will jump to the ID created by the CS1 template. The ID is created from up to four author last names and the year, of the format CITEREFlastname(s)year.

These features are not often used, but can customize the display for use with other styles.

et al. is the abbreviation of the Latin et alii ('and others'). It is used to complete a list of authors of a published work, where the complete list is considered overly long. The abbreviation is widely used in English, thus it is not italicized per MOS:FOREIGN.

There are occasions where Module:Citation/CS1 emits error or maintenance messages because of, or makes changes to, the values assigned to a select set of parameters. Special markup can be used to enforce that a value will nonetheless be accepted as written. The markup for this is ((<value>)), i.e., wrap the entire parameter value in two sets of parentheses. Parameters that support this markup are:

When viewing the page, CS1 templates render the URL to the title to create a link; when printing, the URL is printed. External link icons are not printed.

Not all factually accurate pieces of information about a source are used in a Citation Style 1 citation. Examples of information not included:

This section documents interactions between WP:TemplateData and tools which use that data to edit Wikipedia such as VisualEditor and bots. Before making changes to the TemplateData be aware of these interactions.

Double open brackets [[ are used in a field without closing double brackets ]].
The use of an URL in |author-link= will break the link; this field is for the name of the Wikipedia article about the author, not a website.
Multiple author or editor names are defined and one or more does not show
These parameters are mutually exclusive, and only one will show; by design.