Wikipedia:WikiProject Check Wikipedia/List of errors - Wikipedia

# Priority Cosmetic Error WPC AWB AF Type Reason 01
(dump) Low Yes Template contains useless word "template:" Syntax error Article contains a template that includes the redundant prefix "template:" (eg. {{template:reflist}}). Removing it is usually useful when copying page in another Wikipedia. 02
(dump) High Sometimes <br>, <center> or <small> tag with incorrect syntax. Cases of <span /> and <div />. Syntax error A <br> or <br /> tag (note the slash) are the only standard formats. See the HTML standard for <br> or <small>.
Mediawiki's Tidy tool will be replaced which may cause many now valid tags, such as </br> and <center />, to no longer work. 03
(dump) High No Reference list missing Display problem The article contains one or more <ref> tags, but is missing a {{Reflist}} or <references /> tag 04
(dump) Mid No HTML text style element <a> Display problems The article contains one or more <a> tags. <a> tags will not show up in the rendered article and should use normal wikilink code for external links. 05
(dump) High No Comment tag with no correct end Display problem Missing closing comment tag. <!-- --> 06 Low No DEFAULTSORT with special characters Syntax error Don't use special lettering in DEFAULTSORT 07
(dump) Mid No Headlines all start with three "=" Accessibility First headline starts with "=== XY ===". It should be "== XY ==" header. This causes organisational and accessibility problems. 08
(dump) High No Headline should end with "=" Display problem Headline should end with "=". 09
(dump) Low Yes Multiple categories on one line Against convention Two or more categories on one line. 10 High No Square brackets with no correct end Display problem Found a "[[" brackets with no corresponding "]]" brackets. 11 Off Yes HTML named entities Source readability HTML code found where a Unicode character could be used. For example, ä used instead of ä. It is difficult to comprehend for beginners. 12 Low ? HTML list elements Source readability Detection of <ol>, <ul>...</ul> or <li> tags. Sometimes it is necessary to have these tags, especially in infoboxes. 13
(dump) High No <math> tag without correct match Display problem Missing </math> or <math> tag. 14
(dump) High No <source> tag without correct match Display problem Missing </source> or <source> tag. 15
(dump) High No <code> tag without correct match Display problem Missing </code> or <code> tag. 16
(dump) Low Yes^[a] Unicode control characters Incident detection Detection of Unicode controls such as 0+FEFF, 0+200E, 0+200B and PUA characters. 17
(dump) Low Yes^[a] Category duplication Incident detection Unnecessary duplicate categories found. 18 Off Yes Category's first letter is small Against convention Against convention. If turned on again, check if CamelCase cases (e.g. Category:iPhone) have consensus to be changed to

(e.g. Category:IPhone).

19
(dump) High No Headlines start with one "=" Accessibility A heading section starts with just one "=". This causes organisational and accessibility problems 20
(dump) Low Yes Symbol for dead Source readability The article had a † and not † 21 Off No Category: in English Incident detection [[Category: ]] found when the native language should be used 22 Off Yes Category with space Against convention Category contains an unnecessary space, for example: [[ Category:ABC]] or [[Category : ABC]]. 23
(dump) High No <nowiki> without correct match Display problem Missing </nowiki> or <nowiki> tag. 24
(dump) High No <pre> without correct match Display problem Missing </pre> or <pre> tag. 25
(dump) Mid No Headline hierarchy Accessibility After a section headline "==", there should not be a headline of "====". This causes organisational and accessibility problems. 26
(dump) Low Yes HTML text style element <b> (bold) Accessibility
Source readability Found a <b> tag. Should use wiki markup of '''. See WP:Deviations 27 Off Yes Unicode syntax Source readability © gives very little clue as to what this is supposed to be. Use © or the symbol directly ©. Some entries, like the [ ] brackets should remain in unicode, or converted to {{!(}} and {{!)}} when used in external links. 28
(dump) High No Table with no correct end Display problem An opening table has "{|" tag, but no corresponding closing "|}" tag. 29
(dump) High No <gallery> without correct match Display problem Missing </gallery> or <gallery> tag. 30 Off No Image without alternate description Accessibility 31 Low ? HTML table element Source readability A <table>, <tr> or <td> tag was found. Should use wiki markup instead. 32 High No Double pipe in a link Display problem Article contains a wikilink like [[text|text2|text3]] (displays as text2|text3), [[text||text3]] or [[text|text2||]]. or a broken wikilink inside a table. 33 Off ? HTML text style element <u> (underline) Against convention 34 High No Template programming element Syntax error A template programming element, such as {{{1}}}, #if or #switch, was found. They are usually not needed or a regular template can be substituted instead. 35 Off No Image gallery without description Accessibility 36 Low No Redirect with incorrect syntax Display problem Redirect will not work 37 Low No DEFAULTSORT missing for titles with special letters Display problem Don't use special lettering for sorting. DEFAULTSORT should be set without the special lettering. 38
(dump) Low Yes HTML text style element <i> (italics) Accessibility
Source readability Found a <i> tag. Should use wiki markup of ''. See WP:Deviations 39 Low No HTML text style element <p> Accessibility Found a <p> tag. Usually should use wiki markup's blank line. Some tags, such as <ref> must use <p> due to a wikimedia bug. 40 Low ? HTML text style element <font> Against convention Found a <font> tag. This tag isn't used in HTML5 41 Off ? HTML text style element <big> Against convention Found a <big> tag. This tag isn't used in HTML5 42
(dump) Low ? HTML text style element <strike> Accessibility Found a <strike> tag. This tag isn't used in HTML5. Use <s> instead. However, strikes shouldn't be used at all for accessibility reasons, so removing the strike is usually the best option. 43 High No Template with no correct end Display problem Found a "{{" brackets with no corresponding "}}" brackets. 44 Low No Headlines with bold Against convention A headline is all or partially bold. This should rarely be used and may or not be bold depending on the browser used. 45 Low No Interwiki duplication Display problem Duplicate entry. Now that interwiki links have been moved to wikidata, this error is possibly due to wikilinks that ought to be rendered that omits the leading : in [[:pt:Jorge de Mascarenhas]]. Should often be converted to internal redlinks per WP:BUILD/WP:REDLINK. 46 High No Square brackets without correct beginning Display problem Found a "]]" brackets with no corresponding "[[" brackets. 47 High No Template without correct beginning Display problem Found a "}}" brackets with no corresponding "{{" brackets. 48
(dump) Low No Title linked in text Display problem A wikilink of the article's title was found. This creates an unnecessary circular wikilink per MOS:OVERLINK/WP:SELFREDIRECT and inappropriately bolds the linked word. 49 High No Headline with HTML Accessibility
Source readability Found a headline created with HTML tags <h1>, <h2>, etc. per MOS:DEVIATIONS and MOS:HEAD. 50 Off Yes en dash or em dash 51 Mid No Interwiki before last headline Syntax error With interwikis no long used, this usually means a syntax problem with a interlanguage link, ie [[de:foo]] instead of [[:de:foo]] 52 Low Yes Category before last headline Against convention Categories should be placed in the last section. If a link is intentional, used [[:Category:Foobar]] 53 Mid No Interwiki before last category Syntax error With interwikis no long used, this usually means a syntax problem with a interlanguage link, ie [[de:foo]] instead of [[:de:foo]] 54
(dump) Low No Break in list Accessibility WP:LISTGAP 55
(dump) Low No Double <small> tags Accessibility Causes the text to be smaller than 85%. This goes against accessibility guidelines. 56 Off No Arrow as ASCII art The article had an arrow like "<--" or "-->" or "<==" or "==>". Write better this arrow with the Unicode "←" or "→" or "⇐" or "⇒". 57 Low No Headlines end with a colon Against convention Remove the : 58 Mid No Headline all CAPS Against convention Headlines should normally use sentence case, unless referring to titles of works and all-caps acronyms. 59 Low Yes Template value ends with a <br> Syntax error May cause whitespace errors (unconfirmed as of 2023) 60 High No Template parameter with a problem Syntax error Usually means a broken wikilink inside a template. Can also mean the '=' sign is missing and replaced with another character. 61 Low No Reference before punctuation Display problem <ref> comes after not before various punctuation marks (.,?:;!); see WP:REFPUNC 62 High No URL without http:// Syntax error A URL was found that contained no http://. Example: [en.wikipedia.org Wikipedia] 63 Low No <small> in a <ref>, <sub> or <sup> Accessibility <ref> and <sub> tags already create smaller text. Adding a <small> would cause the text to be smaller than 85%. This goes against accessibility guidelines. 64
(dump) Low Yes Link equal to linktext Syntax error Finds cases of [[Foo|Foo]]. A Visual Editor bug causes wikilinks with italics or bold to be done incorrectly, usually some text outside the wikilink will also be bold or italized. Moreover, WP:NOPIPEDLINK. 65 Low Yes Image description ends with <br> Syntax error Clutter/Does nothing 66 Low No Image description with full <small> Accessibility Image description text is already smaller. Adding a <small> would cause the text to be smaller than 85%. This goes against accessibility guidelines. 67 Off No Reference after punctuation (see 61 instead) 68 Off No Link to other language 69
(dump) Mid No ISBN with incorrect syntax Incorrect content Per WP:ISBN, the correct format is ISBN 978-2345-78383-1. Also finds ISBNs inside external links as Wikimagick doesn't work and ISBN template can cause problems. 70
(dump) Mid No ISBN with wrong length Incorrect content ISBNs should have a length of 10 or 13 characters 71
(dump) Mid No ISBN with wrong position of X Incorrect content X is only allowed in the last position of the ISBN 72
(dump) Mid No ISBN-10 with wrong checksum Incorrect content ISBN checksum is wrong, verify the ISBN 73
(dump) Mid No ISBN-13 with wrong checksum Incorrect content ISBN checksum is wrong, verify the ISBN 74 High No Link with no target Against convention
Incorrect content [[|foobar]] links to foobar. The pipe is either unneeded, someone forgot to give a target, or someone vandalized the article. 75 Off ? Indented list 76 Low ? Link with encoded space Source readability Found a URI encoded space, ie %20, inside a wikilink. This usually indicates a badly constructed external link. 77 Off No Image description with partial <small> 78 Low No Reference list duplication Display problem Found two or more {{reflist}} or <references /> tags 79 Off No External link without description 80 High No External link with a line break Display problem Found a newline character inside an external link or a missing closing bracket. A newline character causes the link not to work. 81 Low ? Reference duplication Saves wikitext, and makes it easier to maintain the article, as you will only need to change one entry to update multiple instances of the same reference 82 Off ? Link to other wikiproject 83
(dump) Mid No Headlines start with three "=" and later with two "=" Accessibility Organisational and accessibility problems. 84 Off No Section without content 85 Low ? Tags without content Source readability An empty <ref></ref> or <span></span> serves no purpose. This can be confusing to editors, and lead to issues if someone interacts with the empty tags by mistake. 86 High No External link with two brackets Display problem Found an external links surround by double brackets.
Example: [[http://www.wikipedia.org Wikipedia]] # Priority Cosmetic Error WPC AWB AF Type Reason 87 Off No HTML named entities without semicolon Display problem 88 Low Yes DEFAULTSORT with a blank at first position Against convention The space in {{DEFAULTSORT: DuBois, Lewis}} is useless and ignored by MediaWiki. 89 Low No DEFAULTSORT with no space after the comma Syntax error The script found a DEFAULTSORT without a space after the comma {{DEFAULTSORT:DuBois,Lewis}}. The causes the article to be sorted as the first DuBois article. 90 Mid No Internal link written as an external link Syntax error The script found an external link that should be replaced with a wikilink. An example would be on enwiki [http://en.wikipedia.org/wiki/Larry_Wall Larry Wall] should be written as [[Larry Wall]]. 91 Mid No Interwiki link written as an external link Syntax error The script found an external link that should be replaced with an interwiki link. An example would be on enwiki [http://fr.wikipedia.org/wiki/Larry_Wall Larry Wall] should be written as [[:fr:Larry Wall]]. 92
(dump) Off No Headline double Accessibility This causes navigation and accessibility issues 93 Mid No External link with double http:// Syntax error The script found an external link that had double http://. An example would be [http://http://www.google.com] 94 Mid No Reference tags with no correct match Display problem A <ref> or </ref> tag was found without the corresponding beginning or ending tag. 95 Low No Editor's signature or link to user or draft space Syntax error See Wikipedia:UPYES and WP:SIGNHERE 96 Mid No Table of Contents after first headline Accessibility TOC should be placed at the end of the lead section of the text, before the first section heading. Users of screen readers do not expect any text between the TOC and the first heading. See WP:TOC. 97 Mid No TOC has material after it and before the first headline Accessibility Screen readers don't process material that comes between the Table of Contents and first headline. See WP:TOC. 98
(dump) High No <sub> with no correct end Display problem Missing </sub> tag. Can cause display problems in Visual Editor and mw:Html5Depurate 99
(dump) High No <sup> with no correct end Display problem Missing </sup> tag. Can cause display problems in Visual Editor and mw:Html5Depurate 100
(dump) Low ? List tag with no correct match Source readability List tag (<ol>, <ul> or <li>) with no correct match. 101
(dump) Low No Ordinal number found inside <sup> tags Against convention Ordinal numbers should be in regular text, not inside <sup> tags See MOS:ORDINAL. 102
(dump) Mid No PMID with incorrect syntax Incorrect content Per WP:PMID, the syntax should be PMID 4957203 Also checks if PMID is inside an external link as Magiclinks and {{PMID}} template won't work. 103
(dump) Mid No Pipe Template inside a wikilink Syntax error The magic word {{!}} shouldn't be used inside a wikilink. | should be used instead. 104
(dump) Mid No Unbalanced quotes in ref name Syntax error The script found unbalanced quotes in a reference tag. For example <ref name="ref 1> 105
(dump) High No Heading should begin with "=" Display problem A heading should begin with a "=". 106
(dump) Mid No ISSN with incorrect syntax Display problem The script found a problem with ISSN syntax. A normal ISSN looks like ISSN 3895-2372 or 3957-957X. There must be a - between the numbers (don't use dashes). Best if {{ISSN}} template is added. Also finds cases where the ISSN is inside an external linkss 107
(dump) Mid No ISSN with wrong length Incorrect content The script checked the ISSN and found it not containing 8 characters. ISSN should have 8 characters. 108
(dump) Mid No ISSN with wrong checksum Incorrect content The script checked the ISSN and found a problem with the checksum in the ISSN. Also see Category:Articles with invalid ISSNs. 109
(dump) High No Include tag error Display problem The script found a problem with opening or closing tags for <includeonly>, <onlyinclude> or <noinclude> tags. This can cause transclusion problems. 110 Off No Include tag found Display problem The script found a <includeonly>, <onlyinclude> or <noinclude> tags. 111
(dump) Off No Ref after last reference list Display problem There are <ref> tags, after the {{reflist}} or <references> tags. 112 Low ? Bad or deprecated css attributes Display problem Bad CSS should be fixed. Deprecated values should be updated for modern rendering. 113 Low No Newline inside a wikilink Display problem Found a newline character inside a wikilink. A newline character causes the wikilink not to work. Note: errors starting at #500 are not detected by CheckWiki, but only by WPC. 501 Bot No Spelling and typography Proposals for fixing spelling and typography based on suggestions. 502 Off Yes Template namespace in template usage Replaced by CW Error #1 503 Off No Internal link in title 504
(dump) Off No Reference in title 505 Off No Image without alternative description 506 Off No Reference with a numeric name 507 Off No Gallery without caption 508 Off No Missing template 509 Off Yes Internal link could be compacted 510 Off No Non working pipe trick 511 Off No Internal link written as external link Replaced by CW Error #90 512 Off No Interwiki link written as external link Replaced by CW Error #91 513
(dump) Off No Internal link inside external link An external links contains an internal link, see Special:LintErrors/wikilink-in-extlink 514 Off No Missing named reference 515 Off ? Title linked in text through redirect link 516 Off Yes <br /> tags in main namespace 517 Off ? strike tags Replaced by CW Error #42 518 Bot ? nowiki tags in main namespace nowiki tags are often not needed in main namespace 519 Off ? a tags in main namespace Replaced by CW Error #4 520 Off ? Weird characters (pawns, snowmen) in main namespace 521 Bot ? Date format in templates 522 Off ? Empty title An empty title (like == <nowiki /> ==) has been detected. 523 Off ? Duplicate image 524 Low ? Duplicate arguments in template calls See Category:Pages using duplicate arguments in template calls 525 Off ? Span tag 526
(dump) Off ? Incorrect date link Incorrect link to a date, like [[1985|2005]] 527 Low ? Reference with different content Reference tags have the same name but different content, see Category:Pages with duplicate reference names 528 Off ? PMID magic link PMID magic links will be removed from MW, see Category:Pages using PMID magic links 529 Off ? ISBN magic link ISBN magic links will be removed from MW, see Category:Pages using ISBN magic links 530 Off ? RFC magic link RFC magic links will be removed from MW, see Category:Pages using RFC magic links 531 Off ? Reference inside reference Reference tags have been found inside an other reference tag 532 Bot ? Missing end tag An opening tag has no matching end tag, see Special:LintErrors/missing-end-tag. 533 Bot ? Multi colon escape A link has been created with a multi colon escape like Test, see Special:LintErrors/multi-colon-escape. 534 Bot ? Bogus image options An image has been created with a bogus option, see Special:LintErrors/bogus-image-options. 535 Bot ? Tidy bug affecting font tags wrapping links Tidy bug affecting font tags wrapping links, see Special:LintErrors/tidy-font-bug. 536 Bot ? Tidy whitespace bug Tidy whitespace bug, see Special:LintErrors/tidy-whitespace-bug. 537 Bot ? Unclosed quotes in heading Unclosed quotes in heading, see Special:LintErrors/unclosed-quotes-in-heading. 538 Bot Yes Whitespace characters after heading Extra whitespace characters are present after a heading (like == Title == ). 539 Bot ? Misnested tags Misnested tags, see Special:LintErrors/misnested-tag. 540 Bot ? Missing end bold/italic Missing end bold/italic, see Special:LintErrors/missing-end-tag. 541 Off ? Obsolete tag Obsolete tag, see Special:LintErrors/obsolete-tag. 542 Bot ? Empty ref tag <ref> tag without any content like <ref></ref>. 543
(dump) Bot ? Pipe in external link like [https://test.org/toto.html| toto]. 544 Off ? Missing end template in a pair A template designed to be paired with another template is alone, like {{col-begin}} without {{col-end}}. 545 Low ? Template with deprecated parameter A template parameter is obsolete, like writing_credits in {{Soundtrack}}. 546 Off ? Article without categories An article doesn't have any category, except for optional maintenance categories. 547
(dump) Off ? Empty list item A list item is empty, like *. 548
(dump) Off ? Punctuation in link A link ends with a punctuation, which should usually be better placed after the link (like [[Test|test,]]). 549
(dump) Off ? Split link A link is split in several parts (like [[Test|te]][[Test|st]]). 550
(dump) Off ? Link without text A link doesn't have any text, so it's not displayed (like [[Test|<nowiki/>]]). 551
(dump) Off ? Empty line A line is only composed of non displayed elements (like ''<nowiki/>''). 552
(dump) Off ? Template ending with }}} A templates end with }}} instead of }}. 553
(dump) Off ? <nowiki /> after internal link An internal link is followed by a <nowiki /> tag. 554
(dump) Off ? <nowiki /> in <gallery>...</gallery> A <nowiki /> tag is inside a <gallery>...</gallery> tag. 555
(dump) Off ? <nowiki /> in the text A <nowiki /> tag is in the text. 556
(dump) Off ? External link External link in the text of the article. 557
(dump) Off ? Missing whitespace before a link A link is just after the preceding text. 558
(dump) Off ? Duplicated reference A reference is used several times for the same text. 559 Off ? Separator between <ref /> tags Consecutive <ref /> tags are not properly separated. 560
(dump) Off ? Duplicated attribute A tag contains the same attribute several time. 561 Off ? Redirection with target text An internal link targets a redirection but display the name of the final target (like [[REDIRECT|TARGET]] with REDIRECT being a redirect to TARGET). 562
(dump) Off ? Consecutive <nowiki /> tags Several <nowiki /> tags are used one after another. 563 Off ? Unused parameters A template has unused empty parameters. 564 Off ? Unknown parameters A template has unknown parameters. 565
(dump) Off ? <nowiki /> tag between bold/italic A <nowiki /> tag is used between bold/italic. 566 Off ? <abbr /> tag Abbreviation should use templates instead of <abbr /> tag. # Priority Cosmetic Error WPC AWB AF Type Reason