Help:CS1 errors

This page describes the error messages reported by the Citation Style 1 and Citation Style 2 citations, what they mean, and how editors might resolve the errors.

Prior to 2013, the CS1|2 templates used the meta-template {{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 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

While most of the Citation Style 1 and Citation Style 2 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 common or skin CSS stylesheet to include:

<syntaxhighlight lang="css" class="" id="" style="" inline="1">.citation-comment {display: inline !important;} /* show all Citation Style 1 error messages */</syntaxhighlight>

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.

The above code is required if you wish see maintenance category messages:

Category:CS1 maintenance (link)

Editors who do not wish to see any of the CS1 error messages can hide them all by updating their common or skin CSS stylesheet to include:

<syntaxhighlight lang="css" class="" id="" style="" inline="1">.citation-comment {display: none;} /* hide all Citation Style 1 error messages */ </syntaxhighlight>

|access-date= requires |url=

Help desk

(error message hidden by default)

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

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

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

Pages with this error are automatically placed in Category:Pages using citations with accessdate and no URL.

|archive-url= requires |archive-date=

Help desk

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

To resolve this error, provide a value for |archive-date=. For web resources archived at archive.org, the archival date can be found in the |archive-url=; for resources archived at webcitation.org, the cache date is included in the archive header.

Pages with this error are automatically placed in Category:Pages with archiveurl citation errors.

|archive-url= requires |url=

Help desk

A properly formatted citation that includes |archive-url= and |archive-date= requires |url=. When the citation includes |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 |url=. For web resources archived at archive.org, the original url can be found in the |archive-url= value; for resources archived at webcitation.org, the original url is included in the archive header.

Pages with this error are automatically placed in Category:Pages with archiveurl citation errors.

|arxiv= required

Help desk

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

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

Pages with this error are automatically placed in Category:CS1 errors: arXiv.

|chapter= ignored

Help desk

Citation Style 1 templates {{cite web}}, {{cite news}}, {{cite journal}}, {{cite press release}}, {{cite podcast}}, {{cite newsgroup}}, and template {{citation}} when {{citation}} uses |work= or any of its aliases, do not support |chapter= or the aliases |contribution=, |entry=, |article=, or |section=.

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

Pages with this error are automatically placed in Category:CS1 errors: chapter ignored.

Check |arxiv= value

Help desk

When Citation Style 1 and Citation Style 2 templates contain |arxiv=, a test is done to see if the arXiv identifier conforms with the arXiv identifier scheme. 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 |arxiv= value is correct.

Pages with this error are automatically placed in Category:CS1 errors: arXiv.

Check |asin= value

Help desk

When Citation Style 1 and Citation Style 2 templates contain |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 |asin= value is correct.

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

Pages with this error are automatically placed in Category:CS1 errors: ASIN.

Check |author-link= value

Help desk

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

To resolve this error, ensure that the |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 Category:CS1 errors: authorlink.

Check date values in: |param1=, |param2=, ...

Help desk

When Citation Style 1 and Citation Style 2 templates contain date-holding parameters, an automated test is done to see if the dates are real dates that comply with a subset of Wikipedia's Manual of Style, specifically 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 |date= caused by errors in |year= or |month=
• more than one date in a date-holding parameter

The MOS section on date ranges describes how to separate dates in a date range. Do not use  , –, or {{spaced ndash}} as these corrupt the metadata. To add an en dash, use the 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 |date= in CS1|2 citations are limited to current year + 1; that is, for 2024, citation dates in 2025 are acceptable but citation dates in 2026 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 |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 15 November 2024 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 Category:CS1 errors: dates.

Examples of unacceptable dates and how to fix them

Issue	Unacceptable	Acceptable
Hyphen (use dash)	date=2002-2003	date=2002–2003
Slash (use dash)	date=2002/2003	date=2002–2003
Month capitalization	date=28 february 1900	date=28 February 1900
Month capitalization	date=28 FEBRUARY 1900	date=28 February 1900
Season capitalization	date=spring 2011	date=Spring 2011
Future date (typo)	date=2102	date=2012
Access date impossibly far in the past (typo)	access-date=1 January 2001	access-date=1 January 2010
Ambiguous date range or year and month	date=2002-03	|date=2002–2003 |date=March 2002
Bad abbreviation	date=Febr. 28, 1900	|date=Feb 28, 1900 |date=February 28, 1900
Nonexistent date	date=February 29, 1900
Comma in month and year	date=February, 1900	date=February 1900
Non-date text	date=2008, originally 2000	date=2008 |orig-year=2000
Zero-padding	date=January 04, 1987	date=January 4, 1987
Date with slashes	date=12/6/87	|date=December 6, 1987 |date=12 June 1987
Two-digit year	date=87-12-06	date=1987-12-06
One-digit month or day	date=2007-3-6	date=2007-03-06
Wikified date	date=[[April 1]], [[1999]]	date=April 1, 1999
"mm-dd-yyyy" or "dd-mm-yyyy" date format	date=07-12-2009	date=July 12, 2009 or |date=December 7, 2009
Approximate or uncertain dates	date=circa 1970 or |date={{circa}} 1970	date=c. 1970

Check |doi= value

Help desk

When Citation Style 1 and Citation Style 2 templates contain |doi=, a test is done to see if the prefix portion of the DOI value contains the proper 10. registry identifier. Additionally, the |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 |doi= value is correct.

Pages with this error are automatically placed in Category:CS1 errors: DOI.

Check |isbn= value

Help desk

Citation Style 1 and Citation Style 2 templates that contain |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 |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 |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 |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 Category:Pages with ISBN errors.

Check |ismn= value

Help desk

Citation Style 1 and Citation Style 2 templates that contain |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 |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 |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 Category:CS1 errors: ISMN.

Check |issn= value

Help desk

Citation Style 1 and Citation Style 2 templates that contain |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 |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 |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 Category:CS1 errors: ISSN.

Check |lccn= value

Help desk

The |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.

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 |lccn= value is correct and that there are no other letters, punctuation, or other characters.

Pages with this error are automatically placed in Category:CS1 errors: LCCN.

Check |message-id= value

Help desk

The |message-id= parameter holds the unique identifier associated with a netnews message. The value in |message-id= is checked to make sure that it contains @ between left and right identifiers. |message-id= is also checked to make sure that the first character is not < and the last character is not >. Module:Citation/CS1 adds the uri news: to the value in |message-id=. If the value in |message-id= is wrapped in <...> characters, the link created fails.

Further validation is not performed.

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

Pages with this error are automatically placed in Category:CS1 errors: message-id.

Check |ol= value

Help desk

The |ol= parameter is the Open Library identifier. The identifier is one or more digits followed by a last character that is either A (authors), M (books), or W (works). Further validation is not performed.

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

Pages with this error are automatically placed in Category:CS1 errors: OL.

Check |pmc= value

Help desk

The |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 |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 Category:CS1 errors: PMC.

Check |pmid= value

Help desk

The |pmid= parameter is the 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 |pmid= value is correct. If you find something that looks like a PMID and begins with "PMC", use |pmc= instead of |pmid=.

Pages with this error are automatically placed in Category:CS1 errors: PMID.

Check |url= scheme

Help desk

External links in Citation Style 1 and Citation Style 2 templates are made from two parts: the title (|title=, |chapter=, etc.) and the URL (|url=, |archive-url=, |chapter-url=, |lay-summary=, etc.). The |url= parameter and other URL parameters must begin with a supported URI scheme. The URI schemes http://, https:// and the protocol relative scheme // are most commonly used; irc://, ircs://, ftp://, news:, mailto: and gopher:// are also supported.

The URL field is checked to ensure that it does not contain spaces. The URL may be protocol relative (begins with //). If there are no spaces and the URL is not protocol relative, then the scheme must comply with RFC 3986. Further validation is not performed.

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

Pages with this error are automatically placed in Category:Pages with URL errors.

Cite uses deprecated parameters

Help desk

(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.

2 parameters

Deprecated parameter	Replace with
coauthor= |coauthors=	|last1=, |first1=, |last2=, |first2=, etc.; or |author1=, |author2=, ...; or |vauthors=; or |authors=
Ref=	ref=

To resolve this error, use an alternate parameter.

Pages with this error are automatically placed in Category:Pages containing cite templates with deprecated parameters.

|coauthors= requires |author=

Help desk

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

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

Pages with this error are automatically placed in Category:CS1 errors: coauthors without author.

|display-editors= suggested

Help desk

(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 |display-editors= to 3 or some lesser value to truncate the editor list. If there are exactly four editors, then set |display-editors= to 4 or higher to display all four editors without including "et al."

Prior to the introduction of 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 book compare

{{ cite book | last=Milquetoast | editor-last=First | first=Caspar | author-link=Caspar Milquetoast | editor3-last=Third | title=If You Won't Think it Presumptuous of Me | editor2-last=Second | editor4-last=Fourth | editor5-last=Fifth }}
Old	Milquetoast, Caspar. First; Second; Third et al. eds. If You Won't Think it Presumptuous of Me.
Live	Milquetoast, Caspar. First; Second; Third; Fourth; Fifth (eds.). 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 |display-editors= parameter, a parameter that was not available to the old-style templates.

Cite book compare

{{ cite book | last=Milquetoast | editor-last=First | first=Caspar | author-link=Caspar Milquetoast | displayeditors=2 | editor3-last=Third | title=If You Won't Think it Presumptuous of Me | editor2-last=Second | editor4-last=Fourth | editor5-last=Fifth }}
Old	Milquetoast, Caspar. First; Second; Third et al. eds. If You Won't Think it Presumptuous of Me.
Live	Milquetoast, Caspar. First; Second; et al. (eds.). If You Won't Think it Presumptuous of Me.

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 |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 Category:Pages using citations with old-style implicit et al. in editors

Empty citation

Help desk

"Empty" may mean that the Citation Style 1 or Citation Style 2 template contains no recognizable parameter identifiers. For example, this citation isn't "empty" because it contains usable information:

{{cite web | http://www.foobar.com | The Foobar Bar}}

The citation is "empty" because it doesn't contain the necessary parameter identifiers (in this case |url= and |title=) that tell {{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 {{citation}} when the intent was to use {{citation needed}} or {{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 Category:Pages with empty citations.

External link in |<param>=

Help desk

This error occurs when any of the CS1 or CS2 citation title-holding parameters – |title=, |chapter=, |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 (|url=, |chapter-url= etc.).

Pages with this error are automatically placed in Category:CS1 errors: external links.

Extra |pages= or |at=

Help desk

This error occurs when CS1 citations attempt to simultaneously use more than one of the parameters: |page=, |pages=, or |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, |page= should be used to specify a single page that is relevant to the cited content, |pages= should be used to specify a range or list of pages (e.g. 37–42) that are relevant, and |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 |pages=, and attempt to use it to indicate the total number of pages in the resource.

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

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

Pages with this error are automatically placed in Category:Pages with citations using conflicting page specifications.

|firstn= missing |lastn= in Authors/Editors list

Help desk

Citation Style 1 and Citation Style 2 templates requires a |lastn= parameter for each |firstn= 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 |lastn= have a matching |firstn=.

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

To resolve this error, ensure that each |firstn= has a corresponding |lastn=.

Pages with this error are automatically placed in Category:CS1 errors: missing author or editor.

|format= requires |url=

Help desk

(error message hidden by default)
(error message hidden by default)

These errors occur when Citation Style 1 and Citation Style 2 templates use |format= or |...-format= without also providing a corresponding URL for |url= or |...-url=, respectively. The |format= and |...-format= parameters are used to specify the file format of a web resource (e.g. PDF, DOC, XLS, etc.). In some cases an editor may have intended to use |type= to specify a kind of document (e.g. hard cover, paperback, pamphlet, etc.) The |format= and |...-format= value is always displayed.

The list of |...-format= parameters is:

|archive-format=, |chapter-format=, |conference-format=, |contribution-format=, |event-format=, |lay-format=, |section-format=, |transcript-format=

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

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

Pages with this error are automatically placed in Category:Pages using citations with format and no URL.

Invalid parameter value

Help desk

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.

Parameters with limited acceptable values

parameter	acceptable values
dead-url=	no, true, y, yes, unfit, usurped
ignore-isbn-error=	true, y, yes
last-author-amp=
mode=	cs1, cs2
name-list-format=	vanc
nopp=	true, y, yes
no-tracking=
registration=
subscription=

To resolve this error, use an appropriate value.

Pages with this error are automatically placed in Category:CS1 errors: invalid parameter value.

Missing |lastn= in Authors/Editors list

Help desk

So that all authors and editors are listed in a rendered citation, Citation Style 1 and Citation Style 2 templates requires n in |lastn= (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 |author1= and |author3= but without |author2= for example).

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

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

To resolve this error, ensure that the numbering of the |lastn= parameters increments properly.

Pages with this error are automatically placed in Category:CS1 errors: missing author or editor.

Missing or empty |title=

There are two slightly different error conditions that can arise when 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.

Bare URL without a title

Help desk

All Citation Style 1 and Citation Style 2 templates report this error when one of the URL-containing parameters cannot be paired with an associated title. This error may also occur when |title= cannot be linked with |url= because the citation also contains a conflicting |title-link= parameter.

URL-containing parameters and associated title parameters

URL parameters	Title parameters
archive-url=	title=
chapter-url=	chapter=, |contribution=, |entry=, |article=
conference-url=	conference=
contribution-url=	chapter=, |contribution=, |entry=, |article=
transcript-url=	transcript=
url=	title=

A unique case exists: if |pmc= has a value and |url= is omitted or empty, then |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 |title= parameter.

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

Pages with this error are automatically placed in Category:Pages with citations having bare URLs.

Citation without a title of any form

Help desk

This error occurs for Citation Style 1 and Citation Style 2 templates when all of the associated title parameters are omitted or left blank. Depending on the type of citation ({{cite web}}, {{cite book}}, {{cite journal}}, etc.), the possible title parameters may include |title=, |chapter=, |article=, |journal=, |book-title=, and so forth. At least one such title parameter must be provided for each citation.

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

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

To resolve this error, provide a value for |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 <ref>...</ref> tags, {{List journal}} may be more appropriate.

Pages with this error are automatically placed in Category:Pages with citations lacking titles.

Missing or empty |url=

Help desk

(error message hidden by default)

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

To resolve this error, provide a value for |url= or use a more appropriate template such as {{cite book}}, {{cite journal}} or other Citation Style 1 or Citation Style 2 template.

Pages with this error are automatically placed in Category:Pages using web citations with no URL.

More than one of |param1=, |param2=, and |param3= specified

Help desk

This error occurs when a Citation Style 1 or Citation Style 2 template includes more than one parameter that maps to the same meaning. For example, |author=, |last=, and |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 Category:Pages with citations having redundant parameters.

Text "????" ignored

Help desk

Unlike many Wikipedia templates, the Citation Style 1 and Citation Style 2 templates do not use unnamed or positional parameters. When a citation contains text between vertical bars 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 %7c. When vertical bars occur in parameter values that are not URLs, replace each vertical bar with |.

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 Category:Pages with citations using unnamed parameters.

|trans-<param>= requires |<param>=

Help desk

Citation Style 1 and Citation Style 2 templates report this error when the citation has an English translation of the title in |trans-title= or chapter title in |trans-chapter= but does not have the original-language title in |title= or original-language chapter title in |chapter=.

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

Pages with this error are automatically placed in Category:CS1 errors: translated title.

Unknown parameter |xxxx= ignored

Help desk

Citation Style 1 and Citation Style 2 templates report this error when the name portion of a parameter's |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 (Xxxx, xxXx, XXXX) but the parameter's name is defined as lowercase (xxxx). The identifier parameters, like |isbn=, |pmc=, |doi=, etc., can be either lower case or upper case, but not of mixed case (|isbn= or |ISBN= but not |Isbn=). For common parameter misspellings, like |pubisher= instead of |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 {{cite web}}, {{cite book}}, {{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 Category:Pages with citations using unsupported parameters.

Unsupported parameter(s) in cite arXiv

Help desk

{{cite arxiv}} uses a limited subset of the common Citation Style 1 parameters. This error message is emitted when parameters not in the {{cite arxiv}} subset occur in a {{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 Category:CS1 errors: arXiv.

URL–wikilink conflict

Help desk

External links in a rendered citation are a combination of url-holding parameters, |url=, |chapter-url=, etc., with title-holding parameters, |title=, |chapter=, etc. Title-holding parameters may be wikilinked 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 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, {{lang}} templates output a wikilinked category. Templates in url-holding parameters may also corrupt the citation's COinS metadata. As a general rule, avoid using templates in title-holding parameters unless you know that the template's affects are entirely visual ({{!}} and the like).

This type of error may also occur in identifier-based templates ({{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 <ref>...</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 Category:CS1 errors: URL–wikilink conflict.

Vancouver style error

Help desk

This error is reported for citations that use |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 (0041–005A, 0061–007A)

C1 Controls and Latin-1 Supplement (00C0–00D6, 00D8–00F6, 00F8–00FF)

Latin Extended-A (0100–017F)

Latin Extended-B (0180–01BF, 01C4–024F)

This error is also reported when a corporate or institutional author is listed in |vauthors= without proper delimiters. Corporate authors should be listed this way:

|vauthors=First Surname FM, Surname AB, ((Corporate or institutional Author)), 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 |vauthors=von Knebel Doeberitz M.

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: |vauthors=Van’t Veer M. Replace this character with the straight (or typewriter) apostrophe: |vauthors=Van't Veer M.

To resolve this error, Romanize author and editor names. Romanizing can result in two-letter initials, for example, the Greek letter 'Θ' Romanizes to 'Th'. 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: |vauthors=..., Tatarinov IuS, ... → |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 Category:CS1 errors: Vancouver style.