Help:CS1 errors

This page describes the error messages reported by the and  citations, what they mean, and how editors might resolve the errors. Category:CS1 errors is the general errors category and Category:CS1 maintenance is the general maintenance category.

Errors issued by Wikipedia's  system, in which citation templates are typically embedded, can be found at w:Help:Cite errors.

Controlling error message display
By default, and  error messages are visible to all readers and maintenance category messages are hidden from all readers.

To display maintenance messages, include the following text in your common CSS page or your specific skin's CSS page (common.css and skin.css respectively):

To display hidden-by-default error messages:

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 null edit will resolve that issue.

To hide normally-displayed error messages:

You can personalize the display of these messages (such as changing the color), but you will need to ask someone who knows CSS or at the technical village pump if you do not understand how.

Most common errors

 * , ~56k pages
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 * , ~9k pages

|access-date= requires |url=


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. 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. 

|archive-url= is malformed


Archive.org allows a variety of URLs to access snapshots of an archived page. Some of these are:
 * – a single snapshot; this is the preferred form for use with archive-url
 * – a wildcard search results page; useful for locating an appropriate snapshot but not appropriate in a citation
 * – incomplete timestamp; archive.org returns the most recent snapshot
 * – saves a new snapshot of the current target; do not use this form

There are two forms of the basic URL:
 * – the old form
 * – the new form

The error message identifies the reason for the message. The reasons are:
 * – the archive.org URL is the save command
 * – web/ was expected but something else was found
 * – the timestamp portion of the URL path is not 14 digits
 * – the flag portion of the URL path (if present; new form URLs only) is not 2 lowercase letters followed by an underscore: 'id_'
 * –  is a deprecated form of the domain name

When the archive.org URL has any of these errors, Module:Citation/CS1 does not link to archive.org and emits an appropriate error message.

To resolve this error, choose the URL of an appropriate snapshot from those held at archive.org. Search for the target URL.

Pages with this error are automatically placed in. 

|archive-url= requires |archive-date=


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 (see acceptable date formats in MOS:DATEFORMAT). 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. 

|archive-url= requires |url=


A properly formatted citation that includes archive-url and archive-date requires url. When the citation includes live, 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. 

<span id="arxiv_missing">|arxiv= required
<section begin="arxiv_missing_help_text" />

requires one, but not both, of the identifier parameters arxiv or eprint to specify an arXiv identifier.

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. <section end="arxiv_missing_help_text" />

<span id="asintld_missing_asin">|asin-tld= requires |asin=
<section begin="asintld_missing_asin_help_text" />

When asin-tld is used in a CS1|2 template, asin or ASIN (with value) must also be present.

To resolve this error, either add the missing ASIN or remove the 'broken' parameter.

Pages with this error are automatically placed in. <section end="asintld_missing_asin_help_text" />

<span id="biorxiv_missing">|biorxiv= required
<section begin="biorxiv_missing_help_text" />

requires the identifier parameter biorxiv.

To resolve this error, ensure that the template has biorxiv with a properly constructed value.

Pages with this error are automatically placed in. <section end="biorxiv_missing_help_text" />

<span id="chapter_ignored">|chapter= ignored
<section begin="chapter_ignored_help_text" />

templates, , , , , , as well as template when it 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, or
 * for cite news, department can be used to give the name of the newspaper's section, such as "Obituaries", or
 * for citation, remove work or its aliases such as website and place their content in title if appropriate

Pages with this error are automatically placed in. <section end="chapter_ignored_help_text" />

<span id="invisible_char">&lt;char> character in |&lt;param>= at position n
<section begin="invisible_char_help_text" />

This error is reported for citations with parameter values that contain invisible or non-printable characters known as control characters; the error includes the position at which the character can be found. Module:Citation/CS1 detects parameter values that contain any of these characters:


 * non-breaking space, U+00A0
 * soft hyphen, U+00AD
 * replacement character, U+FFFD
 * hair space, U+200A
 * zero width space, U+200B
 * zero width joiner, U+200D
 * horizontal tab, U+0009 (HT)
 * line feed, U+0010 (LF)
 * carriage return, U+0013 (CR)
 * delete character, U+007F (DEL)
 * C0 control, U+0000–U+001F (NULL–US)
 * C1 control, U+0080–U+009F (XXX–APC)

To resolve invisible-character errors, remove or replace the identified character. Because these characters are mostly invisible, the error message identifies the character's position in the parameter value counted from the left. Space characters between the assignment operator (the '=' sign) and the parameter value are not counted. If you move through the citation with the arrow keys then the cursor may stand still once at an invisible character which can be removed with or. If you copy-paste a string to the "Characters" field at https://r12a.github.io/app-conversion/ and click "View in UniView" then the position and name of all characters is shown.

Strip markers are special sequences of characters that MediaWiki inserts as a place-holder for certain xml-like tags. These tags include <gallery ></gallery>, <math ></math>, <nowiki ></nowiki>, <pre ></pre>, and <ref ></ref>. The strip markers are replaced with content before the final page rendering. The module ignores math and nowiki strip markers.

To resolve strip marker errors, remove or replace the identified tag. The error message identifies the strip marker's position in the parameter value counted from the left. Space characters between the assignment operator (the '=' sign) and the parameter value are not counted.

Strip marker errors can also be caused by unsupported additional text or templates in parameter values—for example, ISBN in title. Resolve the problem by moving the extraneous text outside of the citation template or by removing the extraneous text or template markup, as appropriate.

Pages with this error are automatically placed in. <section end="invisible_char_help_text" />

<span id="bad_arxiv">Check |arxiv= value
<section begin="bad_arxiv_help_text" />

When and  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. <section end="bad_arxiv_help_text" />

<span id="bad_asin">Check |asin= value
<section begin="bad_asin_help_text" />

When and  templates contain asin, a test is done to see if the ASIN identifier 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.

Pages with this error are automatically placed in. <section end="bad_asin_help_text" />

<span id="bad_asin_tld">Check |asin-tld= value
<section begin="bad_asin-tld_help_text" />

and templates contain a test for known asin-tld values to specify the top-level domain of a given ASIN identifier link. The list of currently supported values is:

,,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,

It is not necessary to provide asin-tld to specify the default (United States). If you want to specify this condition explicitly, a pseudo-value of  can be given to denote this.

All these values are automatically resolved to the correct TLD following one of the schemes,  ,  ,  , and.

If an unsupported value is encountered, the template will issue this error message.

To resolve this error, ensure that the asin-tld value is correct.

If the value is correct, please report this at Help talk:Citation Style 1, so that it can be added to the list of supported values.

Pages with this error are automatically placed in. <section end="bad_asin-tld_help_text" />

<span id="bad_bibcode">Check |bibcode= &lt;message>
<section begin="bad_bibcode_help_text" />

When and  templates contain bibcode, a test is done to see if the bibcode identifier has the proper format. Bibcodes are expected to match these requirements:
 * length must be 19 characters (&lt;message> = ' length ')
 * characters in position(s): (except as specified otherwise, violations produce ' value ' in the &lt;message> portion of the error message):
 * 1–4 must be digits and must represent a year in the range of 1000 – next year (&lt;message> = ' year ')
 * 5 must be a letter
 * 6–8 must be a letter, ampersand, or dot (ampersand cannot directly precede a dot; &. (&lt;message> = ' journal '))
 * 9 must be a letter or dot
 * 10–18 must be a letter, digit, or dot
 * 19 must be a letter or dot

To resolve this error, ensure that the bibcode value is correct.

Pages with this error are automatically placed in. <section end="bad_bibcode_help_text" />

<span id="bad_biorxiv">Check |biorxiv= value
<section begin="bad_biorxiv_help_text" />

When and  templates contain biorxiv, a test is done to see if the bioRxiv identifier has the proper form. There are two valid forms, each beginning with bioRxiv's doi directory indicator and registrant code (10.1101) and followed by:
 * six numeric characters without punctuation or spaces:
 * 10.1101/######
 * – 6-digit bioRxiv identifier
 * ymd format date prefix followed by six numeric characters without punctuation or spaces followed by optional version:
 * 10.1101/yyyy.mm.dd.######v# where:
 * – represents a date no earlier than 11 December 2019 and no later than tomorrow's date; date must be a valid date
 * – 6-digit bioRxiv identifier
 * – optional version indicator

A common error is to include the bioRxiv URL.

To resolve this error, ensure that the biorxiv value is correct.

Pages with this error are automatically placed in. <section end="bad_biorxiv_help_text" />

<span id="bad_citeseerx">Check |citeseerx= value
<section begin="bad_citeseerx_help_text" />

When and  templates contain citeseerx, a test is done to see if the CiteSeerX identifier has the proper format. The expected identifier is the value assigned to the  query key in the URL of a CiteSeerX document. (This query key should not be confused with a Digital Object Identifier: it should not be input as doi.)

For instance, if you want to link to, use 10.1.1.220.7880.

Pages with this error are automatically placed in. <section end="bad_citeseerx_help_text" />

<span id="bad_date">Check date values in: |&lt;param1>=, |&lt;param2>=, ...
<section begin="bad_date_help_text" />

When and  templates contain date-holding parameters, an automated test is done to see if the dates are real dates that comply with a subset of the date rules in  Wikipedia's Manual of Style, specifically checking for violations of MOS:DATEFORMAT.

To resolve this error, ensure that the date is an actual date and that the date format follows the Wikipedia Manual of Style's guidance on dates in the named parameter. See examples of unacceptable dates and how to fix them, below. Or, some conceptual issues to look for:
 * impossible dates, such as 29 February 2011 (2011 was not a leap year)
 * access-date must specify a day, not just a month or year.
 * misplaced, incorrect, or extraneous punctuation
 * extraneous text
 * hyphens or slashes instead of en dashes in date ranges (en dashes are required)
 * misspelling or improper capitalization (see MOS:ALLCAPS for more detail that is not in Wikipedia Manual of Style's guidance on dates)
 * other unacceptable date formats listed in MOS:BADDATEFORMAT
 * more than one date in a date-holding parameter
 * years before 100 AD, including BCE/BC dates. Try using parameter orig-date instead.

See Help: Citation Style 1 for information about limitations in the CS1 citation templates' handling of date formats. The MOS section on date ranges describes how to separate dates in a date range. Do not use,  , or  as these corrupt the metadata. To add an en dash, use the CharInsert edit tool or see How to make dashes. You may also use this one: –. 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, citation dates in are acceptable but citation dates in  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 contains a full date (day, month, and year) and is between 15 January 2001 (the founding date of Wikipedia) and today's date plus one day, 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. <section end="bad_date_help_text" />

<span id="bad_doi">Check |doi= value
<section begin="bad_doi_help_text" />

When and  templates contain doi, a test is done to see if the prefix portion of the DOI value is correctly formatted and has what appears to be a valid registrant code. A proper DOI prefix begins with the  directory indicator. The remaining portion of the prefix is a string of digits and the dot character which form the registrant code. When the directory indicator is, the CS1|2 templates test for a valid registrant code. Valid registrant codes: Additionally, the doi value is checked to make sure that it does not contain spaces, en dashes, does not end with punctuation. Further validation of the DOI is not performed.
 * must be composed of digits
 * must be in the range:
 * 1000–9999
 * 10000–49999
 * may have one or more subcodes that begin with a dot followed by digits (1000.10)
 * must not be 5555 (invalid/temporary/test)

Do not include the  scheme and domain name from a URL. A proper doi value looks like 10.1103/PhysRevLett.80.904.

To resolve this error, ensure that the doi value is correct.

In very rare cases, publishers have released works with a DOI deviating from the standard form. If you are certain that such a non-conforming DOI truly corresponds to the published work, then you can add accept-this-as-written markup around the identifier to suppress the error message. (Do not use this markup for DOIs, which are inactive rather than non-conforming. Instead, use doi-broken-date for them.)

Pages with this error are automatically placed in. <section end="bad_doi_help_text" />

<span id="bad_hdl">Check |hdl= value
<section begin="bad_hdl_help_text" />

When and  templates contain hdl, a test is done to see if the hdl value looks like a properly defined value. The hdl 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 hdl is not performed.

To resolve this error, ensure that the hdl value is correct.

Pages with this error are automatically placed in. <section end="bad_hdl_help_text" />

<span id="bad_isbn">Check |isbn= value
<section begin="bad_isbn_help_text" />

and 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 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. (If relevant, they can be specified using id instead.)

The error message &lt;type> indicator can be:
 * – ISBN is not 10 or 13 digits
 * – ISBN has one or more incorrect digits; look for typos and transposition
 * – ISBN has one or more 'digits' that is not in the allowed set appropriate to ISBN length
 * – 13-digit ISBNs must begin with '978' or '979'
 * – 10-digit ISBNs with the mis-positioned 'X' character
 * – 13-digit ISBN begins with '9790'; this prefix / group ID combination is reserved to ISMN

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 ISBN printed on the work rather than one retrieved from third-party sources. If both are available, use the 13-digit ISBN.. 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 accept-this-as-written markup around the identifier to suppress the error message. In many cases, books may have been reissued with a corrected ISBN. Use a corrected ISBN when possible.

Sometimes there are numbers assigned to isbn that appear to be legitimate – length is right, check digit is correct – but that aren't true ISBN numbers. This tool may be helpful.

See also ISBN.

Pages with this error are automatically placed in. <section end="bad_isbn_help_text" />

<span id="bad_ismn">Check |ismn= value
<section begin="bad_ismn_help_text" />

and 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 COinS. More than one ISMN, or characters that are not part of the ISMN, corrupt the COinS metadata. (If relevant, they can be specified using id instead.)

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. <section end="bad_ismn_help_text" />

<span id="bad_issn">Check |issn= value
<section begin="bad_issn_help_text" />

and templates that contain issn and/or eissn 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 each of ISSN and eISSN is allowed in this field because the whole issn and eissn values are included in the citation's COinS metadata. See also COinS. (If relevant, they can be specified using id instead.)

The ISSN and eISSN are always rendered as two four-digit numbers separated with a hyphen.

To resolve this error, ensure that the issn and eissn values are correct, that only one value per parameter 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'.

In very rare cases, publishers have released works with a malformed identifier. If you are certain that a non-conforming identifier truly corresponds to the published work, then you can add accept-this-as-written markup around the identifier to suppress the error message. In some cases, works may have been reissued with a corrected identifier. Use the corrected one when possible.

Pages with this error are automatically placed in. <section end="bad_issn_help_text" />

<span id="bad_jfm">Check |jfm= value
<section begin="bad_jfm_help_text" />

When and  templates contain jfm, a test is done to see if the JFM identifier value looks like a properly defined value. The jfm identifier is checked to make sure that it has the form:  where   is any digit 0–9. Further validation of the JFM identifier is not performed.

To resolve this error, ensure that the jfm value is correct.

Pages with this error are automatically placed in. <section end="bad_jfm_help_text" />

<span id="bad_jstor">Check |jstor= value
<section begin="bad_jstor_help_text" />

When and  templates contain jstor, a test is done to see if the JSTOR identifier value looks like a properly defined value. Error messages are emitted when the assigned value has some form of the string 'jstor' (case-agnostic), or has a URI scheme ( or  ), or has any space characters.

To resolve this error, ensure that the jstor value is correct.

Pages with this error are automatically placed in. <section end="bad_jstor_help_text" />

<span id="bad_lccn">Check |lccn= value
<section begin="bad_lccn_help_text" />

The lccn parameter is for 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.

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.

When receiving this error, be on the lookout for publishers who omitted leading zeros in the LCCN following the two or four digit year. For example, an LCCN that is properly 92-035427 could be shortened in the printed work to 92-35247. When experimenting with inserting omitted zeroes, cross-check the finished number against the LCCN permalinks online.

Pages with this error are automatically placed in. <section end="bad_lccn_help_text" />

<span id="bad_message_id">Check |message-id= value
<section begin="bad_message_id_help_text" />

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 scheme  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. <section end="bad_message_id_help_text" />

<span id="bad_mr">Check |mr= value
<section begin="bad_mr_help_text" />

When and  templates contain mr, a test is done to see if the MR identifier value looks like a properly defined value. The mr identifier is checked to make sure that it contains only digits and that it is no more than seven digits in length. Further validation of the MR identifier is not performed.

To resolve this error, ensure that the mr value is correct.

Pages with this error are automatically placed in. <section end="bad_mr_help_text" />

<span id="bad_oclc">Check |oclc= value
<section begin="bad_oclc_help_text" />

The oclc parameter is for the OCLC identifier. Only a single OCLC identifier is allowed. (If relevant, multiple OCLCs can be specified using id instead.)

The identifier must be in one of these forms: Further validation is not performed.
 * 1) prefix   followed by 8 digits
 * 2) prefix   followed by 9 digits
 * 3) prefix   followed by 10 (or more) digits
 * 4) prefix   followed by a variable number of digits without leading zeros
 * 5) 1 to 10 (or more) digits without prefix

To resolve this error, ensure that the oclc value is correct.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

A tip for fixing this error: Editors sometimes place valid ISBN, LCCN, ASIN, or other identifiers in oclc.

Pages with this error are automatically placed in. <section end="bad_oclc_help_text" />

<span id="bad_ol">Check |ol= value
<section begin="bad_ol_help_text" />

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

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

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<span id="bad_osti">Check |osti= value
<section begin="bad_osti_help_text" />

The osti parameter is for the Office of Scientific and Technical Information (OSTI) identifier. OSTIs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value between 1018 and. Further validation is not performed.

A common error is to include the OSTI URL, or the OSTI DOI.

To resolve this error, ensure that the osti value is correct.

If the value is correct and lower than 1018 or larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

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<span id="bad_paramlink">Check |&lt;param>-link= value
<section begin="bad_paramlink_help_text" />

These link-holding parameters and their matching title-holding parameters are combined to create a working wikilink to a related article.


 * author-link
 * contributor-link
 * editor-link
 * episode-link
 * interviewer-link
 * series-link
 * subject-link
 * title-link
 * translator-link
 * author
 * contributor
 * editor
 * episode
 * interviewer
 * series
 * subject
 * title
 * translator

(Parameters checked for this error may also be of the form author-linkn or authorn-link.)

This error occurs when any of these &lt;param>-link parameters contain a wikilink or a URL, or they contain any of the characters not permitted in Wikipedia article titles per WP:TITLESPECIALCHARACTERS (except  (underscore), used as a replacement for spaces, and , used as a fragment identifier when linking to article sections). The prohibited characters are:.

The &lt;param>-link parameter value should contain only the title of a Wikipedia article or a link to a section of a Wikipedia article. Module:Citation/CS1 checks the &lt;param>-link parameter values for wikimarkup and for a URI scheme (, , the protocol relative scheme  , etc.). Interlanguage links in any of the &lt;param>-link parameters require a leading colon:

While primarily intended to catch the errors mentioned above, Module:Citation/CS1 will also catch malformed interlanguage wikilinks wherever they occur. Interlanguage wikilinks that have the form:

do not create visible clickable links in the article text. Instead, these links appear in the left pane in the languages list. Module:Citation/CS1 disables interlanguage links in this form and emits an error message. The correct form is:

This error can also be caused when there is a &lt;param>-link value and the matching &lt;param> parameter contains a wikilink.

To resolve this error, do one of the following:
 * Ensure that the &lt;param>-link value is the full name of a Wikipedia article (without brackets) or a section of an article, and not a link to an external web site.
 * Make sure that there are no wikilinks in the matching &lt;param> parameters.
 * If you want to link to a URL outside of Wikipedia, move the link to url or a similar parameter, if one is available in the template you are using.

Pages with this error are automatically placed in. <section end="bad_paramlink_help_text" />

<span id="bad_pmc">Check |pmc= value
<section begin="bad_pmc_help_text" />

The pmc parameter is for 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 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.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

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<span id="bad_pmid">Check |pmid= value
<section begin="bad_pmid_help_text" />

The pmid parameter is for the PubMed identifier. PMIDs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value between 1 and. 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.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

Pages with this error are automatically placed in. <section end="bad_pmid_help_text" />

<span id="bad_rfc">Check |rfc= value
<section begin="bad_rfc_help_text" />

The rfc parameter is for the Internet Engineering Task Force (IETF) RFC identifier (unrelated to Wikipedia's internal RfCs). IETF RFCs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value between 1 and. Further validation is not performed.

To resolve this error, ensure that the rfc value is correct.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

Pages with this error are automatically placed in. <section end="bad_rfc_help_text" />

<span id="bad_sbn">Check |sbn= value
<section begin="bad_sbn_help_text" />

and templates that contain sbn are checked to ensure that the SBN is the proper length (nine digits), that the SBN uses the correct optional separators (simple space or hyphen), and that the final check digit is correct according to the SBN specification. Only one SBN is allowed in this field because the whole sbn value is included in the citation's COinS metadata. See also COinS. More than one SBN, or characters that are not part of the SBN, corrupt the COinS metadata and may also corrupt the link to Special:BookSources.

The error message &lt;type> indicator can be:
 * length – SBN is not 9 digits
 * checksum – SBN has one or more incorrect digits; look for typos and transposition
 * invalid character – SBN has one or more 'digits' that is not in the allowed set
 * invalid form – mis-positioned 'X' check digit

To resolve this error, ensure that the sbn value is correct, that only one SBN is used, that the proper optional separators are used, and that no other text is included. 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 SBN 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 the SBN as printed in your source is refusing to validate, do check both the front matter and the book cover for SBNs. It is not uncommon for the SBN to be misprinted in the front matter but correct on the cover.
 * Do preview your edit and check that the new SBN does now link to the correct source.

In very rare cases, publishers have released books with malformed SBNs. If you are certain that a non-conforming SBN truly corresponds to the published work, then you can add accept-this-as-written markup around the identifier to suppress the error message. In many cases, books may have been reissued with a corrected SBN. Use a corrected SBN when possible.

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<span id="bad_ssrn">Check |ssrn= value
<section begin="bad_ssrn_help_text" />

The ssrn parameter is for the Social Science Research Network identifier. SSRNs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value between 100 and. Further validation is not performed.

To resolve this error, ensure that the ssrn value is correct.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

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<span id="bad_s2cid">Check |s2cid= value
<section begin="bad_s2cid_help_text" />

The s2cid parameter is for the Semantic Scholar corpus identifier. S2CIDs are checked to ensure that the identifier is a simple number without punctuation or spaces with a value between 1 and. Further validation is not performed.

To resolve this error, ensure that the s2cid value is correct.

If the value is correct and larger than the currently configured limit of, please report this at Help talk:Citation Style 1, so that the limit can be updated.

Pages with this error are automatically placed in. <section end="bad_s2cid_help_text" />

<span id="bad_url">Check |url= value
<section begin="bad_url_help_text" />

External links in and  templates are made from two parts: the title (title, chapter, etc.) and the URL (url, archive-url, chapter-url, lay-url, etc.). The url parameter and other URL parameters must begin with a supported URI scheme. The URI schemes,   and the protocol relative scheme   are most commonly used;  ,  ,  ,  ,   and   are also supported.

The URL field is checked to ensure that it contains only Latin characters and 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.

Top- and second-level domain names are checked for proper form. Generally, top-level domain names must be two or more letters; second-level domain names must be two or more letters, digits, or hyphens (first and last character must be a letter or digit). Single-letter second-level domains are supported for: Third- and subsequent-level domain names are not checked. The path portion of the URL is not checked.
 * all cc TLDs (the country code is not validated)
 * the .org TLD
 * certain letters of the .com TLD (q, x, z)
 * certain letters of the .net TLD (i, q)

To resolve this error, ensure that url and other URL parameters contain valid URLs. Online tools are available to internationalize URLs that are written in non-Latin scripts:

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<span id="bad_zbl">Check |zbl= value
<section begin="bad_zbl_help_text" />

When and  templates contain zbl, a test is done to see if the Zbl identifier value looks like a properly defined value. The zbl identifier is checked to make sure that it has the form:  where   is any digit 0–9. Up to three leading zeros in the first quartet may be omitted. Further validation of the Zbl identifier is not performed.

To resolve this error, ensure that the zbl value is correct.

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<span id="param_unknown_empty">Cite has empty unknown parameter: &lt;param>
<section begin="param_unknown_empty_help_text" />

This error message is hidden. To show this error message see Controlling error message display.

This error message highlights CS1|2 templates that hold empty parameters with names that are not known to CS1|2. This error message is a companion to Unknown parameter |xxxx= ignored.

Empty positional parameters, which typically look like two adjacent pipes in a template,, or a pipe and then the end of the template,  , are identified as numbered parameters:. Similarly, a pipe followed by an HTML comment that encloses everything before the next pipe or closing brace,  will be identified as an empty numbered parameter. Parameters that have both a pipe and an equal sign but do not have a name are identified as empty-string parameters:  or   →. Various templates that wrap CS1|2 templates may cause this error when they use constructs like this:. When  does not have a value, the template creates.

To resolve this error, remove the extra pipe, correct the parameter name, or remove the parameter from the CS1|2 template.

Pages with this error are automatically placed in. <section end="param_unknown_empty_help_text" />

<span id="missing_periodical"> Cite &lt;template> requires |&lt;param>
<section begin="missing_periodical_help_text" />

This error message is hidden. To show this error message see Controlling error message display.

These CS1 periodical templates require a periodical parameter. The periodical templates are:

The error message suggests a periodical parameter that matches the template, but there is no requirement to use the suggested parameter; any one of these periodical parameters may be used:
 * journal
 * magazine
 * newspaper
 * periodical
 * website
 * work

In some cases, an incorrect template has been used (e.g. for a web page, book, or standalone document). The appropriate resolution in these cases is to change the incorrect template to, , or a different, more appropriate template.

Pages with this error are automatically placed in. <section end="missing_periodical_help_text" />

<span id="deprecated_params"> Cite uses deprecated parameter |&lt;param>=
<section begin="deprecated_params_help_text" />

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.

To resolve this error, use a supported parameter.

Plan for the future: All non-hyphenated, multiword parameter names are aliases of hyphenated multiword parameter names. The non-hyphenated aliases exist only for legacy support. Editors should expect that support for non-hyphenated parameter names will be withdrawn. Choose the hyphenated form when adding parameters to a citation template. Consider replacing non-hyphenated parameters with the hyphenated equivalents at the same time.

Pages with this error are automatically placed in. <section begin="deprecated_params_table" />

<span id="generic_title">Cite uses generic title
<section begin="generic_title_help_text" />

Articles are listed in this category when Module:Citation/CS1 identifies template title parameters that use place-holder titles. Such titles may have been provided by bots or other tools that are unable to identify the source's correct title. Pages in this category should only be added by Module:Citation/CS1.

CS1|2 maintains a short list of 'titles' that are typically not the title of the cited source. Some examples are:
 * Wayback machine
 * This website is for sale
 * Are you a robot?

To resolve this error, replace the place-holder title with the source's actual title.

Pages with this error are automatically placed in.

See also the maintenance category Category:CS1 maint: archived copy as title.<section end="generic_title_help_text" />

<span id="citeseerx_missing">|citeseerx= required
<section begin="citeseerx_missing_help_text" />

requires the identifier parameter citeseerx.

To resolve this error, ensure that the template has citeseerx with a properly constructed value.

Pages with this error are automatically placed in. <section end="citeseerx_missing_help_text" />

<span id="class_ignored">|class= ignored
<section begin="class_ignored_help_text" />

Only used in templates, class is only appropriate when the template uses YYMM.NNNN or YYMM.NNNNN identifier formats; see Cite arXiv §Usage.

To resolve this error, remove class.

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<span id="contributor_ignored">|contributor= ignored
<section begin="contributor_ignored_help_text" />

Only used in book citations, contributor identifies the author of a contribution, typically an afterword, foreword, introduction, preface, etc., to another (primary) author's work. This error occurs when contributor is used in a template that is not or  or is one of these two templates and one of the work parameter aliases is set.

To resolve this error, choose a more appropriate CS1 or CS2 template or remove contributor.

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<span id="contributor_missing_required_param">|contributor= requires |&lt;param>=
<section begin="contributor_missing_required_param_help_text" />

Only used in book citations, contributor identifies the author of a contribution, typically an afterword, foreword, introduction, preface, etc., to another (primary) author's work. As such, the primary author is required (author or appropriate alias) as is the title of the contribution (contribution).

To resolve this error, include the book's primary author in author1, or last1, first1, or vauthors and include the contribution title in contribution; or remove contributor.

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<span id="doibroken_missing_doi">|doi-broken-date= requires |doi=
<section begin="doibroken_missing_doi_help_text" />

When doi-broken-date is used in a CS1|2 template, doi or DOI (with value) must also be present.

To resolve this error, either add the missing DOI or remove the 'broken' parameter.

Pages with this error are automatically placed in. <section end="doibroken_missing_doi_help_text" />

<span id="err_extra_text_edition">|edition= has extra text
<section begin="extra_text_edition_help_text" />

The templates are responsible for static text rendered in the citation. When edition is used in a template, cs1|2 adds the abbreviation 'ed.' to the value in the parameter so:
 * 1st

renders as:
 * 1st ed.

The templates emit this error message when various forms of,  , or   are found in the value assigned to edition.

To resolve this error, remove the extraneous text from the parameter value.

Pages with this error are automatically placed in. <section end="extra_text_edition_help_text" />

<span id="empty_citation">Empty citation
<section begin="empty_citation_help_text" />

A or  template marked as "Empty" contains no recognizable parameter identifiers. For example, this citation is marked as "empty" even though it contains usable information:

The citation is "empty" because it does not contain the necessary parameter identifiers (in this case url and title) that tell how to use the information that the citation does contain.

A citation is also marked as "empty" when it contains only parameters that it doesn't recognize:

This citation is "empty" because the Italian-language parameters titolo and anno are not recognized as valid parameter names on the English Wikipedia.

"Empty citation" may also mean that an editor meant to use another template entirely. Perhaps the editor used when the intent was to use  or.

To resolve this error, add appropriate parameter identifiers, translate foreign language parameter names to their English equivalents, or replace the CS1/CS2 template with a more appropriate template.

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<span id="explicit_et_al">Explicit use of et al.
<section begin="explicit_etal_help_text" />

This error occurs where a or  template detects that one of the names parameters contains some form of "et al." either as a separate name parameter (et al.) or as a suffix added to a name list (Smith, A.B. et al.) or first name (John, et al.).

This error can occur in any of the author, editor, interviewer, translator, or contributor parameters.

Use the display-authors parameter instead (or other applicable display- parameter), as documented at Help:Citation Style 1.

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<span id="param_has_ext_link">External link in |&lt;param>=
<section begin="param_has_ext_link_help_text" />

This error occurs when any of the CS1 or CS2 citation title-holding parameters – title, chapter, publisher, work or any of its aliases: journal, magazine, newspaper, periodical and website – hold an 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 the external link from the identified parameter. Consider placing the external link in a more appropriate parameter:
 * for chapter, the URL may belong in chapter-url.
 * for other parameters, it may belong in url.

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<span id="first_missing_last">|&lt;first>n= missing |&lt;last>n=
<section begin="first_missing_last_help_text" />

and templates requires a &lt;last>n parameter for each &lt;first>n parameter in a citation. Author, contributor, editor, interviewer, and translator 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 &lt;last>n have a matching &lt;first>n.

To resolve this error, ensure that each &lt;first>n has a corresponding &lt;last>n.

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<span id="format_missing_url">|format= requires |url=
<section begin="format_missing_url_help_text" />

These errors occur when and  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, such as PDF, DOC, or XLS. In some cases an editor may have intended to use type to specify a kind of document, such as hard cover, paperback, or pamphlet. The format and ...-format value is always displayed.

The list of ...-format parameters is:
 * archive-format, article-format, chapter-format, conference-format, contribution-format, entry-format, event-format, lay-format, map-format, section-format, transcript-format

(Citations that relied on the pre-2014, somewhat odd use of url and format may need adjustment in regard to chapter-format.)

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.

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<span id="disp_name">Invalid |display-&lt;names>=&lt;value>
<section begin="disp_name_help_text" />

These error messages are emitted when Module:Citation/CS1 identifies citations that use one or more of the display-&lt;names> parameters with an invalid assigned. An invalid assigned  is a number that is greater than or equal to the number of   in the associated name-list or it is non-numeric text that Module:Citation/CS1 cannot recognize as a form of the keyword.

To resolve this error, do one of the following:
 * Remove the display-&lt;names> parameter from the citation (because "et al." is not appropriate in the citation)
 * Change the  of the display-&lt;names> parameter such that it is less than the number of   in the name-list (thereby truncating the displayed list to the number)
 * Change the  of the display-&lt;names> parameter to , which will cause "et al" to display after the last.

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<span id="invalid_param_val">Invalid &lt;param>=&lt;value>
<section begin="invalid_param_val_help_text" />

To function properly, some parameters are limited to a certain 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.

Letters in values must all be in lower case, as shown below.

To resolve this error, use an appropriate value.

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<span id="script_parameter">Invalid |script-&lt;param>=: &lt;type>
<section begin="script_parameter_help_text" />

The various script-&lt;param> parameters are checked for proper form. When an error is detected, the error message briefly identifies the type of the error:
 * missing title part – the script-&lt;param> parameter has a language-code prefix but is otherwise empty
 * missing prefix – the script-&lt;param> parameter has text but is missing the required language-code prefix; the prefix has the form  or   where   or   is a valid ISO 639-1 or ISO 639-3 language code known to CS1|2 as a language that uses a non-Latin script; the colon  is required
 * unknown language code – the script-&lt;param> parameter has a (possibly valid) language code that CS1|2 does not recognize as a language using a non-Latin script

Language codes known to CS1|2 for languages that do not use a Latin script are:

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<span id="apostrophe_markup">Italic or bold markup not allowed in: |&lt;param>=
<section begin="apostrophe_markup_help_text" />

Italic or bold  wikimarkup is not allowed in publisher and periodical parameters. These parameters include: To resolve this error, remove wiki markup from the named parameter's value and ensure that the template is using the correct parameters; when citing a newspaper, use newspaper for the newspaper's name, not publisher, etc.
 * publisher
 * journal
 * magazine
 * newspaper
 * periodical
 * website
 * work

Pages with this error are automatically placed in. <section end="apostrophe_markup_help_text" />

<span id="missing_name">Missing |&lt;name>n=
<section begin="missing_name_help_text" />

So that all names are listed in a rendered citation, and  templates require n in &lt;last>n (and its aliases) to increment by 1 for each name in the list (author, contributor, editor, interviewer, translator). 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.

To resolve this error, ensure that the numbering of the &lt;last>n parameters increments properly.

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<span id="missing_title">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.

<span id="bare_url_missing_title">Bare URL without a title
<section begin="bare_url_missing_title_help_text" />

All and  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.

A unique case exists for cite journal: if pmc or doi has a value, url is omitted or empty, and title-link does not point to an article, then title is automatically linked with the same URL as the PMC or DOI. This default behaviour can be overridden using none/pmc/doi.

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.

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<span id="citation_missing_title">Citation without a title of any form
<section begin="citation_missing_title_help_text" />

This error occurs for and  templates when all of title, trans-title, and script-title are omitted or left blank. At least one of these title parameters must be provided for each citation.

will show this error if series is omitted or left 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 or one of the  family of templates would have been more appropriate. This error also occurs when an editor used but intended to use.

To resolve this error, provide a value for title, trans-title, and/or script-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, may be more appropriate.

Pages with this error are automatically placed in. <section end="citation_missing_title_help_text" />

<span id="cite_web_url">Missing or empty |url=
<section begin="cite_web_url_help_text" />

This error message is reported by, , and 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 or  template.

Pages with this error are automatically placed in. <section end="cite_web_url_help_text" />

<span id="missing_pipe">Missing pipe
<section begin="missing_pipe_help_text" />

and templates report this error when one parameter has text that looks like it is a parameter missing a pipe. This error occurs when a template parameter value contains characters and digits followed by an equal sign. If the alphanumeric text immediately preceding the equal sign is a valid CS1|2 parameter name, the module assumes that the template is missing a pipe and emits this error message.

Some legitimate titles will contain a CS1|2 parameter name followed by an equal sign. In that case, enclose the equal sign in nowiki tags, like this: <nowiki >=</nowiki>. For most other cases, simply add the missing pipe.

Pages with this error are automatically placed in. <section end="missing_pipe_help_text" />

<span id="redundant_parameters">More than one of |&lt;param1>=, |&lt;param2>=, and |&lt;param3>= specified
<section begin="redundant_parameters_help_text" />

This error occurs when a or  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).

This error occurs when a CS1 or CS2 template uses more than one type of author or editor name-list style. There are three kinds of incompatible author-name-list styles:
 * authorn and lastn / firstn (and their various aliases), vauthors, and authors

and similarly, three editor-name-list styles:
 * editorn and editor-lastn / editor-firstn (and their various aliases) as well as veditors

To resolve this error, choose one name-list-style. Use the chosen style for both of the author and editor name-lists.

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<span id="err_extra_text_pages">|page(s)= has extra text
<section begin="extra_text_pages_help_text" />

The templates are responsible for static text rendered in the citation. When page/p, pages/pp, quote-page or quote-pages is used in a template, cs1|2 inserts the appropriate pagination prefix 'p.' or 'pp.' ahead of the value in the parameter so:
 * 123

renders as:
 * p. 123

and:
 * 123–125

renders as:
 * pp. 123–125

The templates emit this error message when various forms of,  ,  ,  ,  , or   are found in the value assigned to page/p, pages/pp, quote-page or quote-pages.

To resolve this error, remove the extraneous text from the parameter value.

Pages with this error are automatically placed in. <section end="extra_text_pages_help_text" />

<span id="param_access_requires_param">&#124;&lt;param>-access= requires &#124;&lt;param>=
<section begin="param_access_requires_param_help_text" />

This error is reported when an access level has been specified for some external link, but the corresponding required parameter is missing or empty. The parameter can be one of

To resolve this error, either provide a value for the parameter, or remove the access level specification.

Pages with this error are automatically placed in. <section end="param_access_requires_param_help_text" />

<span id="embargo_missing_pmc">|pmc-embargo-date= requires |pmc=
<section begin="embargo_missing_pmc_help_text" />

When pmc-embargo-date is used in a CS1|2 template, pmc or PMC (with value) must also be present.

To resolve this error, either add the missing PMC or remove the 'broken' parameter.

Pages with this error are automatically placed in. <section end="embargo_missing_pmc_help_text" />

<span id="ssrn_missing">|ssrn= required
<section begin="ssrn_missing_help_text" />

requires the identifier parameter ssrn.

To resolve this error, ensure that the template has ssrn with a properly constructed value.

Pages with this error are automatically placed in. <section end="ssrn_missing_help_text" />

<span id="text_ignored">Text "????" ignored
<section begin="text_ignored_help_text" />

Unlike many Wikipedia templates, the and  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 (pipe characters) that are part of URLs or titles. When vertical bars occur in URLs, replace each vertical bar with. When vertical bars occur in parameter values that are not URLs, replace each vertical bar with  or.

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.

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<span id="trans_missing_title">|trans-&lt;param>= requires |&lt;param>= or |script-&lt;param>
<section begin="trans_missing_title_help_text" />

and 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 chapter. Consider adding language if not already part of the citation.

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<span id="parameter_ignored">Unknown parameter |&lt;param>= ignored<span id="parameter_ignored_suggest">
<section begin="parameter_ignored_help_text" /> and templates report this error when the name portion of a parameter's value pair is not recognized as a valid name. Typically, this is caused by spelling or capitalization errors or when a page is reverted to a version where the citation template did support the parameter.

The CS1|2 engine does not ignore unrecognized parameters. The purpose of the citation is to properly identify the source, not to 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). Some 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 !mxt=y). For common parameter misspellings, like pubisher instead of publisher and some former template parameters, CS1|2 will suggest a valid parameter name. The list of deprecated and recently removed parameters may contain additional information as well.

Reported unknown parameters following a DUPLICATE_&lt;param> scheme are created by Citation Bot when it finds duplicate parameters &lt;param> in a template.

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, , , 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.

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<span id="wikilink_in_url">URL–wikilink conflict
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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, 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 effects are entirely visual ( and the like).

This type of error may also occur in identifier-based templates (, 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.

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Vancouver style error
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This error is reported for citations that use vauthors, veditors, 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 more than two initials are used: in case of more than two initials, list only the first two.

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:
 * First Surname FM, Surname AB, Corporate or institutional Author, Last Surname 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, lists Magnus von Knebel Doeberitz as Doeberitz Mv which is not correct. This author's name should be listed as 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: Vant Veer M. Replace this character with the straight (or typewriter) apostrophe: Vant 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 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: ..., Tatarinov IuS, ... → ..., ((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.

Specific Rules for Names: Pages with this error are automatically placed in. <section end="vancouver_help_text" /><section begin="notes_help_text" />
 * Surnames with hyphens and other punctuation in them
 * Other surname rules
 * Given names containing punctuation, a prefix, a preposition, or particle
 * Degrees, titles, and honors before or after a personal name
 * Designations of rank within a family, such as Jr and III
 * Names appearing in non-roman alphabets (Cyrillic, Greek, Arabic, Hebrew, Korean) or character-based languages (Chinese, Japanese)
 * Organizations as author
 * CS1|2 does not obey the semicolon-as-separator rule. Separate corporate and organizational names from each other and from individual names with a comma; wrap corporate and organizational names in doubled parentheses as described above.