Help:Strip markers

This help page is a how-to guide.

It explains concepts or processes used by the Wikipedia community. It is not one of Wikipedia's policies or guidelines, and may reflect varying levels of consensus.

Shortcut

WP:UNIQ

Strip markers are alphanumeric strings of text that are enclosed by ?UNIQ...QINU? in place of expected output but do not normally show. Strip markers are placeholders that the MediaWiki parser inserts to indicate that more complicated content will be included. Strip markers can be exposed when the marker text is changed or truncated after it is inserted, or when badly-formed code causes the parser to be reset, and lose its memory of which strip marker corresponds to which piece of special content.

The MediaWiki software adds elements that look and act like HTML tags. Parser tags are included in MediaWiki whereas extension tags are added by optional software extensions.

For a machine-generated list, see Special:Version#mw-version-parser-extensiontags. It may include tags not documented here.

Parser tags: <gallery>, <includeonly>, <noinclude>, <nowiki>, <onlyinclude>, <pre>

Extension tags: <categorytree>, <charinsert>, <chem> (alias <ce>), <graph>, <hiero>, <imagemap>, <indicator>, <inputbox>, <mapframe>, <maplink>, <math>, <math chem>, <poem>, <ref>, <references>, <score>, <section>, <syntaxhighlight> (alias <source>), <templatedata>, <templatestyles>, <timeline>

Strip markers are used in parsing these extension tags. When a strip marker is exposed by an issue with an extension tag, the name of the tag causing the issue will show in the middle of the string. These tags are used in many templates, so the text is useful in determining the root cause.

Known causes of strip marker exposure:

Tracked in Phabricator
Task T16562

Tracked in Phabricator
Task T27417

A change in the MediaWiki software or a template may cause strip markers to be exposed under certain circumstances. Even when this has been fixed, pages that have not been edited since before the problem was introduced may still show the strip markers due to caching. To resolve this, purge the page. The update to MediaWiki 1.18 in October 2011 is one such instance of this issue. An update to Cite with 1.24wmf13 on July 24, 2014 also exposed the markers.
Using a parser tag inside a #tag construct will expose the strip markers. Examples: <ref> in #tag:nowiki; <nowiki> in #tag:source. T16562
Using <ref> in a piped link will expose the strip markers. T27417
Math markup <math>...</math> in section headings can expose strip markers in the table of contents as of December 2021^[update]. T295091

Wikipedia:Manual of Style/Mathematics#Typesetting of mathematical formulae says section headings should use HTML only.

Search for exposed strip markers: QINU site:en.wikipedia.org

See also