View source for Help:CS1 errors

{{pp-semi-indef}}{{Wikipedia how to}}

This page describes the error messages reported by the {{cs1}} and {{cs2}} citations, what they mean, and how editors might resolve the errors.

Prior to 2013, the CS1|2 templates used the meta-template {{tlx|citation/core}}. In 2013, as part of the [[WP:LUA]] project, Wikipedia editors upgraded the CS1|2 series of templates to use a single [[Lua (programming language)|Lua]] module. [[Module:Citation/CS1]] is the engine that controls how CS1|2 citations are displayed and how citation data are passed to external referencing tools through [[COinS]] metadata. The benefits of the upgrade are enhanced performance, reduced complexity and redundancy, and for the purposes of this page, improved error detection, categorization, and reporting.

==Controlling error message display==
<section begin=control_error_messages_help_text /><section begin=show_error_messages_help_text /><section begin=show_all_messages_help_text />While most of the {{cs1}} and {{cs2}} error messages are visible to all readers, some remain hidden. Editors who wish to see all of the CS1|2 error messages can do so by updating their [[Special:MyPage/common.css|common]] or [[Special:MyPage/skin.css|skin]] CSS stylesheet to include:
:{{code|.citation-comment {display: inline !important;} /* show all Citation Style 1 error messages */||lang=css}}

Even with this css installed, older pages in ''Wikipedia''{{'}}s cache may not have been updated to show these error messages even though the page is listed in one of the tracking categories. A [[WP:NULLEDIT]] will resolve that issue.<section end=show_error_messages_help_text />

The above code is required if you wish see maintenance category messages:
:<span class="citation-comment" style="color:#33aa33">Category:CS1 maintenance ([[:Category:CS1 maintenance|link]])</span><section end=show_all_messages_help_text />

<section begin=hide_error_messages_help_text />Editors who do not wish to see any of the CS1 error messages can hide them all by updating their [[Special:MyPage/common.css|common]] or [[Special:MyPage/skin.css|skin]] CSS stylesheet to include:
:{{code|.citation-comment {display: none;} /* hide all Citation Style 1 error messages */ |lang=css}}<section end=hide_error_messages_help_text /><section end=control_error_messages_help_text />

==<span id="accessdate_missing_url">|access-date= requires |url{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=accessdate_missing_url_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|access-date=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|url=</code></span> (error message hidden by default)

The {{para|access-date}} (or its alias, {{para|accessdate}}) is the date that the online resource addressed by {{para|url}} was added to the article. If {{para|access-date}} has been included in the citation without {{para|url}} then this message appears. If the citation does not use a web link, then {{para|access-date}} is redundant and should be removed.

When the online resource has a publication or other fixed date associated with it, {{para|access-date}} is of limited value though may be useful in identifying an appropriate archived version of the resource. Without {{para|url}}, {{para|access-date}} is not considered useful.

To resolve this error, provide a value for {{para|url}} or remove {{para|access-date}}. Editors should try to determine why the citation has {{para|access-date}} without {{para|url}}. For example, the citation may never have had a {{para|url}}, or {{para|url}} may have been removed because it links to a site that violates the creator's copyright (see [[WP:COPYLINK]]), or because {{para|url}} was deemed to be dead and (mistakenly) removed. If the citation never had {{para|url}} or it was removed for copyright violations, remove {{para|access-date}}. When a dead {{para|url}} has been removed, restore the {{para|url}} and if possible repair it (see [[WP:LINKROT]]).

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages using citations with accessdate and no URL | Category:Pages using citations with accessdate and no URL | [[:Category:Pages using citations with accessdate and no URL]]}}.<ref group="lower-alpha" name="categories" /><section end=accessdate_missing_url_help_text />

==<span id="archive_missing_date">|archive-url= requires |archive-date{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=archive_missing_date_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|archive-url=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|archive-date=</code></span>

{{para|archive-date}} (or its alias, {{para|archivedate}}), identifies the date that the web resource was archived.

To resolve this error, provide a value for {{para|archive-date}}. For web resources archived at archive.org,<ref name="archive.org" /> the archival date can be found in the {{para|archive-url}}; for resources archived at webcitation.org,<ref name="webcitation.org" /> the cache date is included in the archive header.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with archiveurl citation errors | Category:Pages with archiveurl citation errors | [[:Category:Pages with archiveurl citation errors]] }}.<ref group="lower-alpha" name="categories" /><section end=archive_missing_date_help_text />

==<span id="archive_missing_url">|archive-url= requires |url{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=archive_missing_url_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|archive-url=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|url=</code></span>

A properly formatted citation that includes {{para|archive-url}} and {{para|archive-date}} requires {{para|url}}. When the citation includes {{para|dead-url|no}}, the ordering of elements in the rendered citation is changed to put the original url first.

To resolve this error, provide a value for {{para|url}}. For web resources archived at archive.org,<ref name="archive.org" /> the original url can be found in the {{para|archive-url}} value; for resources archived at webcitation.org,<ref name="webcitation.org" /> the original url is included in the archive header.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with archiveurl citation errors | Category:Pages with archiveurl citation errors | [[:Category:Pages with archiveurl citation errors]]}}.<ref group="lower-alpha" name="categories" /><section end=archive_missing_url_help_text />

==<span id="arxiv_missing">|arxiv= required</span>== <!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=arxiv_missing_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|arxiv=</code> required</span>

{{tlx|cite arxiv}} requires one, but not both, of the identifier parameters {{para|arxiv}} or {{para|eprint}}.

To resolve this error, ensure that the template has {{para|arxiv}} or {{para|eprint}} with a properly constructed value.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: arXiv| Category:CS1 errors: arXiv | [[:Category:CS1 errors: arXiv]]}}.<ref group="lower-alpha" name="categories" /><section end=arxiv_missing_help_text />

==<span id="chapter_ignored">|chapter= ignored</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=chapter_ignored_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|chapter=</code> ignored</code></span>

{{cs1}} templates {{tlx|cite web}}, {{tlx|cite news}}, {{tlx|cite journal}}, {{tlx|cite press release}}, {{tlx|cite podcast}}, {{tlx|cite newsgroup}}, and template {{tlx|citation}} when {{tld|citation}} uses {{para|work}} or any of its aliases, do not support {{para|chapter}} or the aliases {{para|contribution}}, {{para|entry}}, {{para|article}}, or {{para|section}}.

To resolve this error, use a more appropriate citation template or place the content of the {{para|chapter}} parameter in {{para|title}}.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: chapter ignored | Category:CS1 errors: chapter ignored | [[:Category:CS1 errors: chapter ignored]]}}.<ref group="lower-alpha" name="categories" /><section end=chapter_ignored_help_text />

==<span id="bad_arxiv">Check |arxiv= value</span>== <!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_arxiv_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|arxiv=</code> value</span>

When {{cs1}} and {{cs2}} templates contain {{para|arxiv}}, a test is done to see if the arXiv identifier conforms with the arXiv identifier scheme.<ref>{{cite web |url=http://arxiv.org/help/arxiv_identifier |title=Understanding the arXiv identifier |website=[[Cornell University Library]] |accessdate=2014-08-20}}</ref> The identifier is checked for a valid number of digits in the article id; valid year and month values; and properly-placed hyphens, slashes, and dots.

To resolve this error, ensure that the {{para|arxiv}} value is correct.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: arXiv| Category:CS1 errors: arXiv | [[:Category:CS1 errors: arXiv]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_arxiv_help_text />

==<span id="bad_asin">Check |asin= value</span>== <!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->

<section begin=bad_asin_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|asin=</code> value</span>

When {{cs1}} and {{cs2}} templates contain {{para|asin}}, a test is done to see if the [[ASIN]] identifier is contains ten upper-case alphanumeric characters without punctuation or spaces and that if the first character is numeric, that the ASIN conforms to the rules for a ten-digit [[ISBN]].  

To resolve this error, ensure that the {{para|asin}} value is correct.

If the {{para|asin}} value is correct and all-numeric, use {{para|isbn}} instead and delete any {{para|asin-tld}} parameters.  Articles with CS1 citations that use {{para|asin}} with all numeric values are categorized in {{cl|CS1 maint: ASIN uses ISBN}}.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: ASIN| Category:CS1 errors: ASIN | [[:Category:CS1 errors: ASIN]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_asin_help_text />

==<span id="bad_authorlink">Check |author-link= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_authorlink_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|author-link=</code> value</span>

The {{para|author-link}} (or any of its aliases, such as {{para|authorlink}}) links an associated {{para|author}} (or {{para|last}} / {{para|first}} pair) parameter value to the author's existing Wikipedia article. It should contain only the Wikipedia article name. [[Module:Citation/CS1]] checks {{para|author-link}} for a [[URI scheme]] (<code>http://</code>, <code>https://</code>, the protocol relative scheme <code>//</code>, etc.).

To resolve this error, ensure that the {{para|author-link}} value is the full name of a Wikipedia article (without brackets), and not a link to an external site.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: authorlink | Category:CS1 errors: authorlink | [[:Category:CS1 errors: authorlink]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_authorlink_help_text />

==<span id="bad_date">Check date values in: |param1=, |param2=, ...</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_date_help_text />{{help desk}}<span class="error">Check date values in: <code style="color:inherit; border:inherit; padding:inherit;">|param1=, |param2=, ...</code></span>

When {{cs1}} and {{cs2}} templates contain date-holding parameters, an automated test is done to see if the dates are real dates that comply with a [[Help:Citation Style 1#Dates|subset]] of Wikipedia's Manual of Style, specifically [[Wikipedia:Manual of Style/Dates and numbers#Dates and years|MOS:BADDATEFORMAT]].

To resolve this error, ensure that the date is an actual date and that the date format follows the Wikipedia Manual of Style in the named parameter. Some things to look for:
*misplaced, incorrect, or extraneous punctuation
*extraneous text
*incomplete year-initial dates
*hyphens instead of en dashes
*misspelling or improper capitalization (see [[MOS:ALLCAPS]] for more detail that is not in the above-linked Dates section)
*date formats listed in [[MOS:BADDATEFORMAT]]
*impossible dates (e.g., 29 February 2011)
*errors in {{para|date}} caused by errors in {{para|year}} or {{para|month}}
*more than one date in a date-holding parameter

[[WP:DATERANGE|The MOS section on date ranges]] describes how to separate dates in a date range. Do not use <code>&amp;nbsp;</code>, <code>&amp;ndash;</code>, or {{tlx|spaced ndash}} as these corrupt the metadata. To add an en dash, use the [[Help:CharInsert#Insert|CharInsert]] edit tool or see [[Wikipedia:How to make dashes]]. A bot is often able to correct the separator, provided the overall format is unambiguous.

Future dates in {{para|date}} in CS1|2 citations are limited to current year + 1; that is, for {{#time:Y}}, citation dates in {{#time:Y|now +1 year}} are acceptable but citation dates in {{#time:Y|now +2 year}} and beyond are not.

Dates prior to 1582 are treated as [[Julian calendar]] dates. Dates from 1582 onward are treated as [[Gregorian calendar]] dates. The Julian calendar was used in some places until approximately 1923. Three Julian calendar dates in the overlap period, 29 February in the years 1700, 1800, and 1900, will cause this error message because those years are not leap years in the Gregorian calendar.

The access date (in {{para|access-date}}) is checked to ensure that it is between 15 January 2001 (the founding date of Wikipedia) and today's date plus one day (currently {{#time:j F Y|today+1 day}} [[UTC]]), because it represents the date that an editor viewed a web-based source to verify a statement on Wikipedia. Because editors may be in time zones that are one day ahead of the UTC date, one extra day is accepted.
 
Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: dates | Category:CS1 errors: dates | [[:Category:CS1 errors: dates]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_date_help_text />

{| class="wikitable"
|+ Examples of unacceptable dates and how to fix them
|-
! Issue !! Unacceptable !! Acceptable
|-
| Hyphen (use dash) || {{para|plain=y|date|2002{{red|-}}2003}} || {{para|plain=y|date|2002{{green|–}}2003}}
|-
| Slash (use dash) || {{para|plain=y|date|2002{{red|/}}2003}} || {{para|plain=y|date|2002{{green|–}}2003}}
|-
| Month capitalization  || {{para|plain=y|date|28 {{red|f}}ebruary 1900}} || {{para|plain=y|date|28 {{green|F}}ebruary 1900}}
|-
| Month capitalization  || {{para|plain=y|date|28 F{{red|EBRUARY}} 1900}} || {{para|plain=y|date|28 F{{green|ebruary}} 1900}}
|-
| Season capitalization || {{para|plain=y|date|{{red|s}}pring 2011}} || {{para|plain=y|date|{{green|S}}pring 2011}}
|-
| Future date (typo) || {{para|plain=y|date|2{{red|10}}2}} || {{para|plain=y|date|2{{green|01}}2}}
|-
| Access date impossibly far in the past (typo) || {{para|plain=y|access-date|1 January 20{{red|01}}}} || {{para|plain=y|access-date|1 January 20{{green|10}}}}
|-
| Ambiguous date range or year and month || {{para|plain=y|date|2002-{{red|03}}}} || {{plainlist|
*{{para|plain=y|date|2002–{{green|20}}03}}
*{{para|plain=y|date|{{green|March}} 2002}}}}
|-
| Bad abbreviation || {{para|plain=y|date|{{red|Febr.}} 28, 1900}} || {{plainlist|
*{{para|plain=y|date|{{green|Feb}} 28, 1900}}
*{{para|plain=y|date|{{green|February}} 28, 1900}}}}
|-
| Nonexistent date || {{para|plain=y|date|{{red|February 29, 1900}}}} ||
|-
| Comma in month and year || {{para|plain=y|date|February{{red|,}} 1900}} || {{para|plain=y|date|February 1900}}
|-
| Non-date text  || {{para|plain=y|date|2008{{red|, originally 2000}}}} || {{para|plain=y|date|2008}} {{green|{{para|plain=y|orig-year|2000}}}}
|-
| Zero-padding  || {{para|plain=y|date|January {{red|04}}, 1987}} || {{para|plain=y|date|January {{green|4}}, 1987}}
|-
| Date with slashes  || {{para|plain=y|date|12{{red|/}}6{{red|/}}87}} || {{plainlist|
*{{para|plain=y|date|{{green|December 6, 19}}87}}
*{{para|plain=y|date|{{green|12 June 19}}87}}}}
|-
| Two-digit year  || {{para|plain=y|date|{{red|87}}-12-06}} || {{para|plain=y|date|{{green|19}}87-12-06}}
|-
| One-digit month or day || {{para|plain=y|date|2007-{{red|3}}-{{red|6}}}} || {{para|plain=y|date|2007-{{green|03}}-{{green|06}}}}
|-
| Wikified date || {{para|plain=y|date|{{red|&#91;[}}April 1{{red|]]}}, {{red|&#91;[}}1999{{red|]]}} }} || {{para|plain=y|date|{{green|April 1, 1999}}}}
|-
| "mm-dd-yyyy" or "dd-mm-yyyy" date format || {{para|plain=y|date|{{red|07-12-}}2009}} || {{para|plain=y|date|{{green|July 12,}} 2009}} or {{para|plain=y|date|{{green|December 7,}} 2009}}
|-
|Approximate or uncertain dates || {{para|plain=y|date|{{red|circa}} 1970}} or {{para|plain=y|date|{{red|<nowiki>{{circa}}</nowiki>}} 1970}} ||{{para|plain=y|date|{{green|c.}} 1970}}
|-
|}

==<span id="bad_doi">Check |doi= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_doi_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|doi=</code> value</span>

When {{cs1}} and {{cs2}} templates contain {{para|doi}}, a test is done to see if the prefix portion of the [[Digital object identifier|DOI]] value contains the proper <code>10.</code> registry identifier. Additionally, the {{para|doi}} value is checked to make sure that it does not contain spaces or en dashes and does not end with punctuation. Further validation of the DOI is not performed.

To resolve this error, ensure that the {{para|doi}} value is correct.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: DOI | Category:CS1 errors: DOI | [[:Category:CS1 errors: DOI]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_doi_help_text />

==<span id="bad_isbn">Check |isbn= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_isbn_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|isbn=</code> value</span>

{{cs1}} and {{cs2}} templates that contain {{para|isbn}} are checked to ensure that the [[ISBN]] is the proper length (ten or thirteen digits), that the ISBN uses the correct optional separators (simple space or hyphen), and that the final [[check digit]] is correct according to the ISBN specification. Only one ISBN is allowed in this field because the whole {{para|isbn}} value is included in the citation's [[COinS]] [[metadata]]. See also [[Wikipedia:COinS]]. More than one ISBN, or characters that are not part of the ISBN, corrupt the COinS metadata and may also corrupt the link to [[Special:BookSources]].

To resolve this error, ensure that the {{para|isbn}} value is correct, that only one ISBN is used, that the proper optional separators are used, and that no other text is included. Use the 13-digit ISBN ''when it is available''. When a 10-digit ISBN is used, if the check digit is a lowercase 'x', change it to an uppercase 'X'.

*'''Do not''' try to resolve the error by simply recalculating the check digit.  The check digit is there to check whether the main part of the number is correct.  If the ISBN is failing to validate, it is likely that there is a typo in the main part of the number.  In this case, recalculating the check digit results in an apparently valid ISBN that leads to the wrong source (or to nowhere).
*If you only have a 10-digit ISBN, '''do''' use the number as-is, do not try to convert it to the 13-digit form.
*If the ISBN as printed in your source is refusing to validate, '''do''' check both the front matter and the book cover for ISBNs.  It is not uncommon for the ISBN to be misprinted in the front matter but correct on the cover.
*'''Do''' preview your edit and check that the new ISBN does now link to the correct source.

In very rare cases, publishers have released books with malformed ISBNs. If you are certain that a non-conforming ISBN truly corresponds to the published work, then you can add {{para|ignore-isbn-error|true}} to the citation in order to suppress the error message. In many cases, books may have been reissued with a corrected ISBN. Use a corrected ISBN when possible.

See also [[Wikipedia:ISBN]].

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with ISBN&#32;errors | Category:Pages with ISBN errors | [[:Category:Pages with ISBN errors]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_isbn_help_text /><!-- See [[bugzilla:47049]] about {{FULLPAGENAME}}, category pagenames containing ISBN, and #ifeq: -->

==<span id="bad_ismn"/>Check |ismn= value==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_ismn_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|ismn=</code> value</span>

{{cs1}} and {{cs2}} templates that contain {{para|ismn}} are checked to ensure that the [[ISMN]] is the proper length (thirteen digits), that the ISMN uses the correct optional separators (simple space or hyphen), and that the final [[check digit]] is correct according to the ISMN specification. Only one ISMN is allowed in this field because the whole {{para|ismn}} value is included in the citation's [[COinS]] [[metadata]]. See also [[Wikipedia:COinS]]. More than one ISMN, or characters that are not part of the ISMN, corrupt the COinS metadata.

To resolve this error, ensure that the {{para|ismn}} value is correct, that only one ISMN is used, that the proper optional separators are used, and that no other text is included. Make sure that the ISMN contains exactly 13 digits.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: ISMN | Category:CS1 errors: ISMN | [[:Category:CS1 errors: ISMN]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_ismn_help_text />

==<span id="bad_issn">Check |issn= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_issn_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|issn=</code> value</span>

{{cs1}} and {{cs2}} templates that contain {{para|issn}} are checked to ensure that the [[ISSN]] is the proper length (eight digits) and that the final [[check digit]] validates according to the ISSN specification. Only one ISSN is allowed in this field because the whole {{para|issn}} value is included in the citation's [[COinS]] [[metadata]]. See also [[Wikipedia:COinS]]. The ISSN is always rendered as two four-digit numbers separated with a hyphen.

To resolve this error, ensure that the {{para|issn}} value is correct, that only one ISSN is used, and that no other text is included (allowable characters are 0-9, X, and -). If the check-digit is a lowercase 'x', change it to an uppercase 'X'.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: ISSN | Category:CS1 errors: ISSN | [[:Category:CS1 errors: ISSN]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_issn_help_text /><!-- See [[bugzilla:47049]] about {{FULLPAGENAME}}, category pagenames containing ISBN, and #ifeq: -->

==<span id="bad_lccn">Check |lccn= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_lccn_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|lccn=</code> value</span>

The {{para|lccn}} parameter is the [[Library of Congress Control Number]] identifier. It is checked to ensure that the identifier is the proper length and has the correct initial digits.

LCCN is a character string 8–12 characters long. The length of the LCCN dictates the character type of the initial 1–3 characters; the rightmost eight are always digits.<ref>{{cite web |url=http://www.loc.gov/marc/lccn-namespace.html#syntax |title=The LCCN Namespace |website=Network Development and MARC Standards Office |publisher=[[Library of Congress]] |date=November 2003}}</ref>
{|class="wikitable"
|+LCCN format description
!Length!!Description
|-
|8 || all characters are digits
|-
|9 || first character is a lower case letter
|-
|10|| first two characters are either both lower case letters or both digits
|-
|11|| first character is a lower case letter, second and third characters are either both lower case letters or both digits
|-
|12|| first two characters are both lower case letters
|-
|}

Further validation is not performed.

To resolve this error, ensure that the {{para|lccn}} value is correct and that there are no other letters, punctuation, or other characters.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: LCCN | Category:CS1 errors: LCCN | [[:Category:CS1 errors: LCCN]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_lccn_help_text />

==<span id="bad_message_id">Check |message-id= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_message_id_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|message-id=</code> value</span>

The {{para|message-id}} parameter holds the unique identifier associated with a netnews message.<ref>{{cite web |url=//tools.ietf.org/html/rfc5536 |title=Netnews Article Format |website=[[Internet Engineering Task Force]] |at=[//tools.ietf.org/html/rfc5536#section-3.1.3 3.1.3]|id=rfc5536 |date=November 2009}}</ref>  The value in {{para|message-id}} is checked to make sure that it contains <code>@</code> between left and right identifiers. {{para|message-id}} is also checked to make sure that the first character is not <code><</code> and the last character is not <code>></code>. [[Module:Citation/CS1]] adds the uri <code>news:</code> to the value in {{para|message-id}}.  If the value in {{para|message-id}} is wrapped in <code><...></code> characters, the link created fails.

Further validation is not performed.

To resolve this error, ensure that the {{para|message-id}} value is correct, that it contains <code>@</code> and is not wrapped in <code><...></code> characters.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: message-id | Category:CS1 errors: message-id | [[:Category:CS1 errors: message-id]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_message_id_help_text />

==<span id="bad_ol">Check |ol= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_ol_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|ol=</code> value</span>

The {{para|ol}} parameter is the [[Open Library]] identifier. The identifier is one or more digits followed by a last character that is either <code>A</code> (authors), <code>M</code> (books), or <code>W</code> (works). Further validation is not performed.

To resolve this error, ensure that the {{para|ol}} value is correct. Do not include "OL" in the value.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: OL | Category:CS1 errors: OL | [[:Category:CS1 errors: OL]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_ol_help_text />

==<span id="bad_pmc">Check |pmc= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_pmc_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|pmc=</code> value</span>

The {{para|pmc}} parameter is the [[PubMed Central]] identifier. PMCs are sequential numbers beginning at 1 and counting up. [[Module:Citation/CS1]] checks the PMC identifier to make sure that the value is a number greater than zero and less than 5000000 and that the identifier contains only digits. Further validation is not performed.

To resolve this error, ensure that the {{para|pmc}} value is correct, and that there are no letters, punctuation, or other characters. Do not include "PMC" in the value. 

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: PMC | Category:CS1 errors: PMC | [[:Category:CS1 errors: PMC]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_pmc_help_text />

==<span id="bad_pmid">Check |pmid= value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_pmid_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|pmid=</code> value</span>

The {{para|pmid}} parameter is the [[PubMed#PubMed identifier|PubMed identifier]]. PMIDs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value greater than or equal to 1 and less than or equal to 30000000. Further validation is not performed.

To resolve this error, ensure that the {{para|pmid}} value is correct. If you find something that looks like a PMID and begins with "PMC", use {{para|pmc}} instead of {{para|pmid}}.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: PMID | Category:CS1 errors: PMID | [[:Category:CS1 errors: PMID]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_pmid_help_text />

==<span id="bad_url">Check |url= scheme</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bad_url_help_text />{{help desk}}<span class="error">Check <code style="color:inherit; border:inherit; padding:inherit;">|url=</code> scheme</span>

External links in {{cs1}} and {{cs2}} templates are made from two parts: the ''title'' ({{para|title}}, {{para|chapter}}, etc.) and the ''URL'' ({{para|url}}, {{para|archive-url}}, {{para|chapter-url}}, {{para|lay-summary}}, etc.). The {{para|url}} parameter and other URL parameters must begin with a supported [[URI scheme]]. The URI schemes <code>http://</code>, <code>https://</code> and the protocol relative scheme <code>//</code> are most commonly used; <code>irc://</code>, <code>ircs://</code>, <code>ftp://</code>, <code>news:</code>, <code>mailto:</code> and <code>gopher://</code> are also supported.

The URL field is checked to ensure that it does not contain spaces.  The URL may be protocol relative (begins with <code>//</code>).  If there are no spaces and the URL is not protocol relative, then the scheme must comply with <nowiki>RFC 3986</nowiki>.<ref>{{citation |mode=cs1 |contribution-url=http://tools.ietf.org/html/std66#section-3.1 |contribution=Scheme |title=Uniform Resource Identifier (URI): Generic Syntax |publisher=[[Internet Engineering Task Force]] |date=January 2005}}</ref> Further validation is not performed.

To resolve this error, ensure that {{para|url}} and other URL parameters contain valid URLs.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with URL errors | Category:Pages with URL errors | [[:Category:Pages with URL errors]]}}.<ref group="lower-alpha" name="categories" /><section end=bad_url_help_text />

==<span id="deprecated_params">Cite uses deprecated parameters==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=deprecated_params_help_text />{{help desk}}<span class="error">Cite uses deprecated parameters</span> (error message hidden by default)

Over time, some parameters have become obsolete or unnecessary.  When this happens, the parameters are identified as deprecated.  Editors are encouraged to use other parameters that accomplish the same purpose as those that have been deprecated. The CS1|2 deprecated parameters are listed in the following table, along with recommended replacement parameters. Parameter names are case-sensitive. Editors should expect that support for deprecated parameters will be withdrawn. 

{|class="wikitable"
|+Deprecated CS1{{pipe}}2 parameters
!Deprecated parameter!!Replace with 
|-
|{{para|coauthor}}<br/>{{para|coauthors}}||{{plainlist|
*{{para|last1}}, {{para|first1}}, {{para|last2}}, {{para|first2}}, etc.; or
*{{para|author1}}, {{para|author2}}, ...; or
*{{para|vauthors}}; or
*{{para|authors}}}}
|-
|{{para|Ref}}||{{para|ref}}
|}

To resolve this error, use an alternate parameter.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages containing cite templates with deprecated parameters‎ | Category:Pages containing cite templates with deprecated parameters‎ | [[:Category:Pages containing cite templates with deprecated parameters]]}}.<ref group="lower-alpha" name="categories" /><section end=deprecated_params_help_text />

==<span id="coauthors_missing_author">|coauthors= requires |author{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=coauthors_missing_author_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|coauthors=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|author=</code></span>

{{para|coauthor}} and {{para|coauthors}} are deprecated parameters. Where they exist without accompanying {{para|author}}, {{para|authors}}, or {{para|last}}, the content of {{para|coauthor}} or {{para|coauthors}} is not displayed.

To resolve this error, use {{para|author1}}, {{para|author2}}, etc., or use {{para|last1}}, {{para|first1}}, {{para|last2}}, {{para|first2}}, etc. to individually list all authors.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: coauthors without author | Category:CS1 errors: coauthors without author | [[:Category:CS1 errors: coauthors without author]]}}.<ref group="lower-alpha" name="categories" /><section end=coauthors_missing_author_help_text />

==<span id="displayeditors">|display-editors= suggested</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=displayeditors_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|display-editors=</code> suggested</span> (error message hidden by default)

To resolve this error for cited sources with more than four editors, add the remaining editors to the citation or set {{para|display-editors}} to <code>3</code> or some lesser value to truncate the editor list. If there are exactly four editors, then set {{para|display-editors}} to <code>4</code> or higher to display all four editors without including "et al."

Prior to the introduction of [[WP:LUA|Lua]]-based citations, the citation formatting templates were designed to support no more than four editors. Specifically, if four (or more) editor parameters were specified, then the template would display three editor names followed by "et al." to indicate that the list had been truncated. Some editors relied on this behavior to include the "et al." label. For example:

{{cite compare |mode=book |editor-last=First |editor2-last=Second |editor3-last=Third |editor4-last=Fourth |editor5-last=Fifth |last=Milquetoast |first=Caspar |author-link=Caspar Milquetoast |title=If You Won't Think it Presumptuous of Me}}

The Lua-based citation templates can accommodate an arbitrarily large number of editors. The Lua-based templates can also explicitly include an "et al." label with the new {{para|display-editors}} parameter, a parameter that was not available to the old-style templates.

{{cite compare |mode=book |editor-last=First |editor2-last=Second |editor3-last=Third |editor4-last=Fourth |editor5-last=Fifth |last=Milquetoast |first=Caspar |author-link=Caspar Milquetoast |title=If You Won't Think it Presumptuous of Me |displayeditors=2}}

The old-style templates supported at most four editors. The new Lua-based templates cannot know if ''Wikipedia'' editors created citations with exactly four editors because there were only four editors or, because old-style citations were limited to four editors. This error message is reported by citations with exactly four editors but without {{para|display-editors}}. To preserve the behavior of old-style citations, Lua-based citations display "et al." in place of the fourth editor.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages using citations with old-style implicit et al. in editors| Category:Pages using citations with old-style implicit et al. in editors| [[:Category:Pages using citations with old-style implicit et al. in editors]]}}<ref group="lower-alpha" name="categories" /><section end=displayeditors_help_text />

==<span id="empty_citation">Empty citation</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=empty_citation_help_text />{{help desk}}<span class="error">Empty citation</span>

"Empty" may mean that the {{cs1}} or {{cs2}} template contains no recognizable parameter identifiers. For example, this citation isn't "empty" because it contains usable information:
:<code><nowiki>{{cite web | http://www.foobar.com | The Foobar Bar}}</nowiki></code>
The citation is "empty" because it doesn't contain the necessary parameter identifiers (in this case {{para|url}} and {{para|title}}) that tell {{tlx|cite web}} how to use the information that the citation does contain.

"Empty" may also mean that an editor meant to use another template entirely. Perhaps the editor used {{tlx|citation}} when the intent was to use {{tlx|citation needed}} or {{tlx|quote}}.

To resolve this error, add appropriate parameter identifiers or replace the CS1|2 template with a more appropriate template.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with empty citations | Category:Pages with empty citations | [[:Category:Pages with empty citations]]}}.<ref group="lower-alpha" name="categories" /><section end=empty_citation_help_text />

==<span id="param_has_ext_link">External link in |<param>=</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=param_has_ext_link_help_text />{{help desk}}<span class="error">External link in <code style="color:inherit; border:inherit; padding:inherit;">|<param>=</code></span>

This error occurs when any of the [[Help:Citation Style 1|CS1]] or [[Help:Citation Style 2|CS2 citation]] title-holding parameters –  {{para|title}}, {{para|chapter}}, {{para|work}} or any of their aliases – hold a properly formatted external link (URL). External links in these parameters corrupt the citation's metadata and can be the source of a variety of other error messages.

To resolve this error, remove external link syntax and put the url in the appropriate parameter ({{para|url}}, {{para|chapter-url}} etc.).

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: external links | Category:CS1 errors: external links | [[:Category:CS1 errors: external links]]}}.<ref group="lower-alpha" name="categories" /><section end=param_has_ext_link_help_text />

==<span id="extra_pages">Extra |pages= or |at=</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=extra_pages_help_text />{{help desk}}<span class="error">Extra <code style="color:inherit; border:inherit; padding:inherit;">|pages=</code> or <code style="color:inherit; border:inherit; padding:inherit;">|at=</code></span>

This error occurs when [[Help:Citation Style 1|CS1 citations]] attempt to simultaneously use more than one of the parameters: {{para|page}}, {{para|pages}}, or {{para|at}}. Each of these parameters is meant to provide a different way of specifying the location within a larger work, of the cited content, that is, of the specific page(s) or place in a cited source that contains the information that supports the article text.  Only one of these parameters is displayed in any rendered citation. According to their intended purpose, {{para|page}} should be used to specify a single page that is relevant to the cited content, {{para|pages}} should be used to specify a range or list of pages (e.g. 37–42) that are relevant, and {{para|at}} should be used to indicate a location in the larger work that is not a numbered page (e.g. "back cover"). Sometimes, editors misunderstand the meaning of {{para|pages}}, and attempt to use it to indicate the total number of pages in the resource.

When {{para|page}} is used with either or both of {{para|pages}} or {{para|at}}, only the {{para|page}} value is displayed. Similarly, when {{para|pages}} is used with {{para|at}}, only the {{para|pages}} value is displayed.

To resolve this error, remove the inappropriate parameter(s).

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations using conflicting page specifications | Category:Pages with citations using conflicting page specifications | [[:Category:Pages with citations using conflicting page specifications]]}}.<ref group="lower-alpha" name="categories" /><section end=extra_pages_help_text />

==<span id="first_missing_last">|first''n''= missing |last''n''= in Authors/Editors list</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->

<section begin=first_missing_last_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|first''n''=</code> missing <code style="color:inherit; border:inherit; padding:inherit;">|last''n''=</code> in Authors list<br /><code style="color:inherit; border:inherit; padding:inherit;">|first''n''=</code> missing <code style="color:inherit; border:inherit; padding:inherit;">|last''n''=</code> in Editors list</span>

{{cs1}} and {{cs2}} templates requires a {{para|last''n''}} parameter for each {{para|first''n''}} parameter in a citation. Author and editor lists are checked for proper last/first pairing.  CS1|2 will emit this error message for the first mismatch it detects.  If there are more last/first mismatches in a citation, subsequent mismatches are not detected.

There is no requirement that each {{para|last''n''}} have a matching {{para|first''n''}}.

The error message uses a sort of shorthand: {{para|last''n''}} can refer to any of the legitimate {{para|author}} aliases in the authors list.  Similarly, {{para|last''n''}} refers to any of the {{para|editor-last}} aliases in the editors list.

To resolve this error, ensure that each {{para|first''n''}} has a corresponding {{para|last''n''}}. 

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | CS1 errors: missing author or editor| CS1 errors: missing author or editor | [[:Category:CS1 errors: missing author or editor]]}}.<ref group="lower-alpha" name="categories" /><section end=first_missing_last_help_text />

==<span id="format_missing_url">|format= requires |url{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=format_missing_url_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|format=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|url=</code></span> (error message hidden by default)<br /><span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|...-format=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|...-url=</code></span> (error message hidden by default)

These errors occur when {{cs1}} and {{cs2}} templates use {{para|format}} or {{para|...-format}} without also providing a corresponding URL for {{para|url}} or {{para|...-url}}, respectively. The {{para|format}} and {{para|...-format}} parameters are used to specify the file format of a web resource (e.g. [[PDF]], [[Doc (computing)|DOC]], [[Microsoft Excel file format|XLS]], etc.). In some cases an editor may have intended to use {{para|type}} to specify a kind of document (e.g. hard cover, paperback, pamphlet, etc.) The {{para|format}} and {{para|...-format}} value is always displayed.

The list of {{para|...-format}} parameters is:
:{{para|archive-format}}, {{para|chapter-format}}, {{para|conference-format}}, {{para|contribution-format}}, {{para|event-format}}, {{para|lay-format}}, {{para|section-format}}, {{para|transcript-format}}

As of 29 November 2014, {{para|chapter-format}} is a new parameter.  Citations that relied on the old, somewhat odd use of {{para|url}} and {{para|format}} may need adjustment.

To resolve this error, remove {{para|format}} or {{para|chapter-format}}; define {{para|url}} or {{para|chapter-url}}; or change {{para|format}} to {{para|type}} (or to {{para|chapter-format}} if {{para|chapter-url}} is used without {{para|url}}.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages using citations with format and no URL | Category:Pages using citations with format and no URL | [[:Category:Pages using citations with format and no URL]]}}.<ref group="lower-alpha" name="categories" /><section end=format_missing_url_help_text />

==<span id="invalid_param_val">Invalid parameter value</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=invalid_param_val_help_text />{{help desk}}<span class="error">Invalid <code style="color:inherit; border:inherit; padding:inherit;">|<parameter>=<value></code></span>

To function properly, some parameters are limited to a certain set set of acceptable values.  This error message indicates that a parameter has been assigned a value that is not a member of the parameter's defined set of acceptable values. 
{|class="wikitable"
|+Parameters with limited acceptable values
|-
!parameter !! acceptable values
|-
|{{para|dead-url}}||<code>no</code>, <code>true</code>, <code>y</code>, <code>yes</code>, <code>unfit</code>, <code>usurped</code>
|-
|{{para|ignore-isbn-error}}||rowspan=2|<code>true</code>, <code>y</code>, <code>yes</code>
|-
|{{para|last-author-amp}}
|-
|{{para|mode}}||<code>cs1</code>, <code>cs2</code>
|-
|{{para|name-list-format}}||<code>vanc</code>
|-
|{{para|nopp}}||rowspan=4|<code>true</code>, <code>y</code>, <code>yes</code>
|-
|{{para|no-tracking}}
|-
|{{para|registration}}
|-
|{{para|subscription}}
|-
|}

To resolve this error, use an appropriate value.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: invalid parameter value | Category:CS1 errors: invalid parameter value | [[:Category:CS1 errors: invalid parameter value]]}}.<ref group="lower-alpha" name="categories" /><section end=invalid_param_val_help_text />

==<span id="missing_name">Missing |last''n''= in Authors/Editors list</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->

<section begin=missing_name_help_text />{{help desk}}<span class="error">Missing <code style="color:inherit; border:inherit; padding:inherit;">|last''n''=</code> in Authors list<br/>Missing <code style="color:inherit; border:inherit; padding:inherit;">|last''n''=</code> in Editors list</span>

So that all authors and editors are listed in a rendered citation, {{cs1}} and {{cs2}} templates requires ''n'' in {{para|last''n''}} (and its aliases) to increment by 1 for each author or editor.  This error message is emitted when there is a 'hole' in the numbering (an author list made up of {{para|author1}} and {{para|author3}} but without {{para|author2}} for example).

The test will not detect a 'hole' that is larger than 1.  It is presumed that when {{para|author''n''}} and {{para|author''n+1''}} are both not present, then the test has reached the end of the list.

The error message uses a sort of shorthand: {{para|last''n''}} can refer to any of the legitimate {{para|author}} aliases in the authors list.  Similarly, {{para|last''n''}} refers to any of the {{para|editor-last}} aliases in the editors list.

To resolve this error, ensure that the numbering of the {{para|last''n''}} parameters increments properly. 

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | CS1 errors: missing author or editor| CS1 errors: missing author or editor | [[:Category:CS1 errors: missing author or editor]]}}.<ref group="lower-alpha" name="categories" /><section end=missing_name_help_text />

==<span id="missing_title">Missing or empty |title{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
There are two slightly different error conditions that can arise when [[Help:Citation Style 1|CS1 citations]] lack appropriate titles. In each case, CS1 reports this error message. The necessary resolution may vary depending on the cause of the error. The error message links to the appropriate description below.

===<span id="bare_url_missing_title">Bare URL without a title</span>===<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=bare_url_missing_title_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">&#124;<param>=</code> missing title</span>

All {{cs1}} and {{cs2}} templates report this error when one of the [[URL]]-containing parameters cannot be paired with an associated title. This error may also occur when {{para|title}} cannot be linked with {{para|url}} because the citation also contains a conflicting {{para|title-link}} parameter.

{|class="wikitable"
|+URL-containing parameters and associated title parameters
|-
!URL parameters
!Title parameters
|-
| {{para|archive-url}}
| {{para|title}}
|-
|{{para|chapter-url}}
| {{para|chapter}}, {{para|contribution}}, {{para|entry}}, {{para|article}}
|-
| {{para|conference-url}}
| {{para|conference}}
|-
| {{para|contribution-url}}
| {{para|chapter}}, {{para|contribution}}, {{para|entry}}, {{para|article}}
|-
| {{para|transcript-url}}
| {{para|transcript}}
|-
| {{para|url}}
| {{para|title}}
|}

A unique case exists: if {{para|pmc}} has a value and {{para|url}} is omitted or empty, then {{para|title}} is linked with the same URL as the PMC.

Because URLs are ugly and generally uninformative, it is expected that editors should provide a meaningful title for each URL. In most cases this can be accomplished by using the {{para|title}} parameter.

To resolve this error, provide an appropriate title for the URL-containing parameter. In the case where {{para|url}} and {{para|title-link}} are contending for {{para|title}} you must choose which one to keep. Consider moving {{para|url}} or {{para|title-link}} to a more suitable parameter.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations having bare URLs | Category:Pages with citations having bare URLs | [[:Category:Pages with citations having bare URLs]]}}.<ref group="lower-alpha" name="categories" /><section end=bare_url_missing_title_help_text />

===<span id="citation_missing_title">Citation without a title of any form</span>===<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=citation_missing_title_help_text />{{help desk}}<span class="error">Missing or empty <code style="color:inherit; border:inherit; padding:inherit;">&#124;title=</code></span>

This error occurs for {{cs1}} and {{cs2}} templates when all of the associated title parameters are omitted or left blank. Depending on the type of citation ({{tlx|cite web}}, {{tlx|cite book}}, {{tlx|cite journal}}, etc.), the possible title parameters may include {{para|title}}, {{para|chapter}}, {{para|article}}, {{para|journal}}, {{para|book-title}}, and so forth. At least one such title parameter must be provided for each citation.

{{tl|cite episode}} will show this error if {{para|series}} is blank (even if a {{para|title}} is provided).

Sometimes this error occurs because an editor has used a CS1|2 citation as a [[Help:Shortened footnotes|shortened footnote]] when {{tlx|sfn}} or one of the {{tlx|harv}} family of templates would have been more appropriate. This error also occurs when an editor used {{tlx|citation}} but intended to use {{tlx|citation needed}}.

To resolve this error, provide a value for {{para|title}} or replace the CS1|2 template with a more appropriate template. If you are listing a periodical or an issue of a periodical in a bibliography rather than within {{tag|ref}} tags, {{tlx|List journal}} may be more appropriate.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations lacking titles | Category:Pages with citations lacking titles | [[:Category:Pages with citations lacking titles]]}}.<ref group="lower-alpha" name="categories" /><section end=citation_missing_title_help_text />

==<span id="cite_web_url">Missing or empty |url{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=cite_web_url_help_text />{{help desk}}<span class="error">Missing or empty <code style="color:inherit; border:inherit; padding:inherit;">|url=</code></span> (error message hidden by default)

This error message is reported by {{tlx|cite web}}, {{tlx|cite podcast}}, and {{tlx|cite mailing list}} when the template parameters {{para|url}} and {{para|archive-url}} are both missing, blank or not properly entered. Note that {{para|website}} or {{para|work}} is the name of the site, not the URL.

To resolve this error, provide a value for {{para|url}} or use a more appropriate template such as {{tl|cite book}}, {{tl|cite journal}} or other {{cs1}} or {{cs2}} template.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages using web citations with no URL | Category:Pages using web citations with no URL | [[:Category:Pages using web citations with no URL]]}}.<ref group="lower-alpha" name="categories" /><section end=cite_web_url_help_text />

==<span id="redundant_parameters">More than one of |param1=, |param2=, and |param3= specified</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=redundant_parameters_help_text />{{help desk}}<span class="error">More than one of <code style="color:inherit; border:inherit; padding:inherit;">|param1=</code>, <code style="color:inherit; border:inherit; padding:inherit;">|param2=</code>, and <code style="color:inherit; border:inherit; padding:inherit;">|param3=</code> specified</span>

This error occurs when a {{cs1}} or {{cs2}} template includes more than one parameter that maps to the same meaning. For example, {{para|author}}, {{para|last}}, and {{para|last1}} are all synonyms of each other, so no more than one of these parameters should ever be used in a single template.

To resolve this error, remove or modify the redundant parameter(s).

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations having redundant parameters | Category:Pages with citations having redundant parameters | [[:Category:Pages with citations having redundant parameters]]}}.<ref group="lower-alpha" name="categories" /><section end=redundant_parameters_help_text />

==<span id="text_ignored">Text "????" ignored</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=text_ignored_help_text />{{help desk}}<span class="error">Text "????" ignored</span>

Unlike many Wikipedia templates, the {{cs1}} and {{cs2}} templates do not use unnamed or positional parameters. When a citation contains text between [[vertical bar]]s and that text does not contain an equal sign (=), CS1|2 ignores the text and reports the error. This is true even when the text is the name of a valid parameter.

This error can also be caused by vertical bars that are part of URLs or titles. When vertical bars occur in URLs, replace each vertical bar with <code>%7c</code>. When vertical bars occur in parameter values that are not URLs, replace each vertical bar with <code>&amp;#124;</code>.

To resolve this error, remove the extraneous text, add '=', add an appropriate parameter name from the template you're using to complete the parameter, or properly encode vertical bars in URLs and titles.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations using unnamed parameters | Category:Pages with citations using unnamed parameters | [[:Category:Pages with citations using unnamed parameters]]}}.<ref group="lower-alpha" name="categories" /><section end=text_ignored_help_text />

==<span id="trans_missing_title">|trans-<param>= requires |<param>{{=}}</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=trans_missing_title_help_text />{{help desk}}<span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|trans-title=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|title=</code></span><br /><span class="error"><code style="color:inherit; border:inherit; padding:inherit;">|trans-chapter=</code> requires <code style="color:inherit; border:inherit; padding:inherit;">|chapter=</code></span>

{{cs1}} and {{cs2}} templates report this error when the citation has an English translation of the title in {{para|trans-title}} or chapter title in {{para|trans-chapter}} but does not have the original-language title in {{para|title}} or original-language chapter title in {{para|chapter}}.

To resolve this error, provide the original language title for {{para|title}} or chapter title for {{para|title}}. Consider adding {{para|language}} if not already part of the citation.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: translated title | Category:CS1 errors: translated title | [[:Category:CS1 errors: translated title]]}}.<ref group="lower-alpha" name="categories" /><section end=trans_missing_title_help_text />

==<span id="parameter_ignored">Unknown parameter |xxxx= ignored</span><span id="parameter_ignored_suggest"> </span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=parameter_ignored_help_text />{{help desk}}<span class="error">Unknown parameter <code style="color:inherit; border:inherit; padding:inherit;">|xxxx=</code> ignored<br />Unknown parameter <code style="color:inherit; border:inherit; padding:inherit;">|xxxx=</code> ignored (<code style="color:inherit; border:inherit; padding:inherit;">|yyyy=</code> suggested)</span>

{{cs1}} and {{cs2}} templates report this error when the name portion of a parameter's {{para|name|value}} pair is not recognized as a valid name. Typically, this is caused by spelling or capitalization errors.

With the old-style citation templates, it was possible to include information within the template that was simply ignored as unrecognized parameters. The Lua-based CS1|2 engine does not ignore unrecognized parameters. The purpose of the citation is to properly identify the source; not act as a repository of notes and ancillary information.

CS1|2 template parameters are lower case. CS1|2 will report this error when the parameter's name contains uppercase letters ({{!xt|Xxxx, xxXx, XXXX}}) but the parameter's name is defined as lowercase ({{xt|xxxx}}). The identifier parameters, like {{para|isbn}}, {{para|pmc}}, {{para|doi}}, etc., can be either lower case or upper case, but not of mixed case ({{xt|{{para|isbn}}}} or {{xt|{{para|ISBN}}}} but not {{!xt|{{para|Isbn}}}}). For [[Module:Citation/CS1/Suggestions|common parameter misspellings]], like {{para|pubisher}} instead of {{para|publisher}}, CS1|2 will suggest a valid parameter name.

To resolve this error, replace the erroneous parameter name with a correct one, possibly using the suggested name. Ensure that the parameter's name is correctly spelled and that there are no characters except spaces between the parameter's name and the leading vertical bar (|) or trailing equals sign (=). A list of valid parameters can be found by consulting [[Help:Citation Style 1]] or visiting the description page of the specific template being used, such as {{tlx|cite web}}, {{tlx|cite book}}, {{tlx|cite journal}}, etc. Consider moving information associated with the unknown parameter into an appropriate parameter or to a section of the article's talk page for preservation.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:Pages with citations using unsupported parameters | Category:Pages with citations using unsupported parameters | [[:Category:Pages with citations using unsupported parameters]]}}.<ref group="lower-alpha" name="categories" /><section end=parameter_ignored_help_text />

==<span id="arxiv_params_not_supported">Unsupported parameter(s) in cite arXiv</span>== <!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=arxiv_params_not_supported_help_text />{{help desk}}<span class="error">Unsupported parameter(s) in cite arXiv</span>

{{tlx|cite arxiv}} uses a limited subset of the common {{cs1}} parameters.  This error message is emitted when parameters not in the {{tld|cite arxiv}} subset occur in a {{tld|cite arxiv}} template.

To resolve this error, remove the unsupported parameters.  See [[Template:Cite arxiv]] for the complete list of supported parameters.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: arXiv| Category:CS1 errors: arXiv | [[:Category:CS1 errors: arXiv]]}}.<ref group="lower-alpha" name="categories" /><section end=arxiv_params_not_supported_help_text />

==<span id="wikilink_in_url">URL–wikilink conflict</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=wikilink_in_url_help_text />{{help desk}}<span class="error">URL–wikilink conflict</span>

External links in a rendered citation are a combination of url-holding parameters, {{para|url}}, {{para|chapter-url}}, etc., with title-holding parameters, {{para|title}}, {{para|chapter}}, etc. Title-holding parameters may be [[wikilink]]ed to another Wikipedia article but not when there is a matching url-holding parameter in the citation. When this condition occurs, the wikilink is suppressed, the wiki markup ignored, and the rendered citation links to the external site.

Some [[Help:Template|templates]] will also cause this error if they are part of a title-holding parameter. The error occurs when the template produces wikilinked content. For example, {{tlx|lang}} templates output a wikilinked category. Templates in url-holding parameters may also corrupt the citation's [[WP:COinS|COinS]] metadata. As a general rule, avoid using templates in title-holding parameters unless you know that the template's affects are entirely visual ({{tlx|!}} and the like).

This type of error may also occur in identifier-based templates ({{tlx|cite doi}}, etc.). When this happens, the error message is shown in the article but the error is actually located in the identifier-based citation template.

To resolve this error, remove wikilinks from title-holding parameters that are intended to be externally linked or remove the external URL, which will allow the internal wikilinks to work as expected. If wikilink-producing templates are important to the citation, move them out of the CS1 template but leave them inside the citation's {{tag|ref}} tags. Some of the functionality provided by templates may also be available through CS1 parameters.

To resolve errors in identifier-based citation templates, the template must be edited to correct the error. Exercise caution when editing these templates because identifier-based citation templates are often used in multiple articles.
CS1 errors: URL–wikilink conflict
Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: URL–wikilink conflict | Category:CS1 errors: URL–wikilink conflict | [[:Category:CS1 errors: URL–wikilink conflict]]}}.<ref group="lower-alpha" name="categories" /><section end=wikilink_in_url_help_text />

==<span id="vancouver">Vancouver style error</span>==<!-- do not remove or change span id without also changing links in Module:Citation/CS1 -->
<section begin=vancouver_help_text />{{help desk}}<span class="error">Vancouver style error</span>

This error is reported for citations that use {{para|name-list-format|vanc}}. [[Vancouver style]] restricts author or editor names to the Latin alphabet. For the purposes of this test, [[Module:Citation/CS1]] defines the Latin alphabet as the letters defined in the [[Unicode]] Latin character sets:
:C0 Controls and Basic Latin<ref>{{cite web |url=http://www.unicode.org/charts/PDF/U0000.pdf |title=C0 Controls and Basic Latin |website=[[Unicode]] |accessdate=2015-04-19}}</ref> (0041–005A, 0061–007A)
:C1 Controls and Latin-1 Supplement<ref>{{cite web |url=http://www.unicode.org/charts/PDF/U0080.pdf |title=C1 Controls and Latin-1 Supplement |website=Unicode |accessdate=2015-04-19}}</ref> (00C0–00D6, 00D8–00F6, 00F8–00FF)
:Latin Extended-A<ref>{{cite web |url=http://www.unicode.org/charts/PDF/U0100.pdf |title=Latin Extended-A |website=Unicode |accessdate=2015-04-19}}</ref> (0100–017F)
:Latin Extended-B<ref>{{cite web |url=http://www.unicode.org/charts/PDF/U0180.pdf |title=Latin Extended-B |website=Unicode |accessdate=2015-04-19}}</ref> (0180–01BF, 01C4–024F)

This error is also reported when a corporate or institutional author is listed in {{para|vauthors}} without proper delimiters.  Corporate authors should be listed this way:
:{{para|vauthors|First Surname FM, Surname AB, {{green|((}}Corporate or institutional Author{{green|))}}, Lastsurname XY}}

While normally correct, sometimes the names listed on a PMID page contain errors when the author surname has a lowercase [[nobiliary particle]].  For example, PMID 17726700 lists Magnus von Knebel Doeberitz as Doeberitz Mv which is not correct.  This author's name should be listed as {{para|vauthors|von Knebel Doeberitz M}}.<ref>{{cite web |url=http://www.ncbi.nlm.nih.gov/books/NBK7282/box/A33081/ |title=Other surname rules |website=National Center for Biotechnology Information}}</ref>

Certain punctuation will be flagged as an error.  For example, Unicode U+2019, right single quotation mark, causes an error because it is not a member of the Latin character sets identified above: {{para|vauthors|Van{{red|’}}t Veer M}}.  Replace this character with the straight (or typewriter) apostrophe: {{para|vauthors|Van{{green|'}}t Veer M}}.

To resolve this error, Romanize author and editor names.<ref>{{cite book |last=Patrias |first=K |editor-last=Wendling |editor-first=D |location=Bethesda |publisher=National Library of Medicine |date=2007 |chapter=Names in non-roman alphabets or character-based languages |chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK7258/box/A48818/ |title=Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers [Internet]. |edition=2nd |name-list-format = vanc}}</ref>  Romanizing can result in two-letter initials, for example, the Greek letter 'Θ' Romanizes to 'Th'.<ref>{{cite web |url=http://www.loc.gov/catdir/cpso/romanization/greek.pdf |title=Greek |website=Library of Congress}}</ref> When author names have this kind of initial, Module:Citation/CS1 can't know if the this kind of initial is a typo or a legitimate Romanized character so it will emit the Vancouver error.  To suppress the error after determining that the two-character initial is correct and not a typo, treat the name as if it were a corporate name by wrapping it in doubled parentheses: {{para|vauthors|...,  Tatarinov IuS, ...}} → {{para|vauthors|...,  ((Tatarinov IuS)), ...}}

Similarly, Chinese hyphenated given names may appear in PubMed listings.  For example: 'Wang Hsien-yu' may be listed on PubMed as 'Wang Hy' which will result in a Vancouver error.  When this occurs, and upon verification that such names are correct, wrap them in doubled parentheses.

Pages with this error are automatically placed in {{#ifeq: {{FULLPAGENAME}} | Category:CS1 errors: Vancouver style | Category:CS1 errors: Vancouver style | [[:Category:CS1 errors: Vancouver style]]}}.<ref group="lower-alpha" name="categories" /><section end=vancouver_help_text /><section begin=notes_help_text />

==Notes==
{{reflist |group=lower-alpha |refs=
<ref group="lower-alpha" name="categories">Pages in the Book talk, Category talk, Draft, Draft talk, Education Program talk, File talk, Help talk, MediaWiki talk, Module talk, Portal talk, Talk, Template talk, TimedText talk, User, User talk, and Wikipedia talk namespaces are not included in the error tracking categories.</ref>
}}<section end=notes_help_text />
<section begin=references_help_text />
==References==
{{reflist |refs=
<ref name="archive.org">{{cite web |url=http://www.archive.org |title=archive.org website}}</ref>
<ref name="webcitation.org">{{cite web |url=http://www.webcitation.org |title=webcitation.org website}}</ref>
}}<section end=references_help_text />

{{Wikipedia referencing}}
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