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{{short description|Project page on technical restrictions for page names}}
{{pp-semi-indef|small=yes}}
{{redirects here|Wikipedia:Technical restrictions|technical restrictions on editing privileges|Wikipedia:User access levels|technical restrictions on external links|WP:Spam blacklist|technical restrictions of MediaWiki template mechanism|Wikipedia:Template limits}}
{{Subcat guideline|naming convention|Technical restrictions|WP:NCTR}}
{{Naming conventions}}
Some [[Help:Page name|page names]] are not possible because of limitations imposed by the MediaWiki software. In some cases (such as names which should begin with a lowercase letter, like [[eBay]]), a template can be added to the article to cause the title header to be displayed as desired. In other cases (such as names containing restricted characters) it is necessary to adopt and display a different title. This page describes appropriate ways to handle these situations.

==Restrictions and workarounds==
Restrictions on page titles are listed at {{section link|Wikipedia:Page name|Technical restrictions and limitations}}. The most commonly encountered problems are that:
*titles cannot begin with a lowercase letter;
*titles cannot contain certain restricted characters.

There are two basic ways of handling a situation where the desired title of a page is technically impossible:
*Use the magic word [[WP:DISPLAYTITLE|DISPLAYTITLE]] to change the way the title header is displayed on the page (although the stored page name is not affected). This is often done through a template, the most common one being {{tl|lowercase}}, which causes the title to be displayed with an initial lowercase letter, as in [[iPod]].
*If this is not possible (due to restrictions on DISPLAYTITLE), choose a different title for the page, and use a template such as {{tl|correct title}} to place a hatnote stating what the correct title should be. This is normally necessary in the case of restricted characters.

These templates should never be [[Wikipedia:Template substitution|substituted (subst)]]. To see which articles have these naming problems you can click on "What links here" in the toolbox for each template. If the template is substituted, it will no longer be linked.

Before declaring the current title to be "wrong" with the "correct title" template (or one of the more specific templates), please consider whether the title you are proposing as "correct" would really comply with Wikipedia conventions, particularly [[Wikipedia:Naming conventions (use English)]], [[Wikipedia:Manual of Style (capital letters)]] and [[Wikipedia:Manual of Style (trademarks)]].

==Lowercase first letter==
{{Shortcut|WP:NCLOWERCASEFIRST}}
The MediaWiki software is configured so that a page title on the English Wikipedia (as stored in the database) cannot begin with a lower-case letter, and links that begin with a lower-case letter are treated as if capitalized, i.e. <tt><nowiki>[[foo]]</nowiki></tt> is treated the same as <tt><nowiki>[[Foo]]</nowiki></tt>.

Examples of articles affected by this problem are:

*'''eBay''', located at [[EBay]]
*'''{{nowrap|{{mvar|e}} (mathematical constant)}}''', located at {{nowrap|[[E (mathematical constant)]]}}
*'''iOS''', located at [[IOS]] (and various articles beginning with: {{Search link|iOS}})
*'''man page''', located at [[Man page]]
*'''pH''', located at [[PH]]
*'''p:Machinery''', located at [[P:Machinery]]

Examples of categories affected by this problem are:

*'''Category:macOS''', located at [[:Category:MacOS]] (and subcategories beginning with macOS)

Example of template affected by this problem:

*'''Template:iPhone models''', located at [[:Template:IPhone models]]

This also means that the page [[Long s]], on the character '''ſ''', cannot be moved to (or redirected from) [[ſ]], as '''ſ''' is a lowercase letter whose uppercase form is [[S]].

To fix this problem, you can place the {{tlx|lowercase title}} wiki markup at the top of the article, category or template page (and optionally at the top of their talk/discussion page). This will cause the page title to be displayed with the initial letter in lowercase, as at [[eBay]]. Note that it does not fix every occurrence, like Wikipedia search bar [[search suggest drop-down list]] feature and Search results, as well as the page history, edit, log pages, or the browser [[address bar]] (it only affects the page title on the rendered HTML page and tab/window title bars).

==Forbidden characters==
{{Shortcut|WP:NCHASHTAG|WP:FORBIDDEN}}
Due to clashes with various elements of the MediaWiki software, some characters (and "characters") are ''not'' allowed to be part of page titles (nor are they supported by [[WP:DISPLAYTITLE|DISPLAYTITLE]]).

===Clashes with wiki markup/HTML syntax===
The following characters are forbidden due to clashes with [[Help:Wiki markup|wiki markup]] and [[HTML]] syntax:

:<code># < > [ ] { } |</code>
For articles about these characters, see [[number sign]], [[less-than sign]], [[greater-than sign]], [[bracket]] (covers several characters), and [[vertical bar]], respectively.

If the desired title of an article contains any of these characters, then an alternative title must be used instead. Often, you can simply remove the characters (e.g. [[MARRS]] instead of ''M|A|R|R|S''). However, it may be necessary to spell out the character (e.g. [[C-sharp]] instead of ''C#'') or use another substitute. Note that the sharp sign ♯ (different from the keyboard # character) ''can'' be used, as in [[C♯ (musical note)]].

In any of these cases, a hatnote should be placed at the top of the article informing readers what the correct title is. This is done using one of the following templates:
*{{tlx|Correct title|''Correct title''|reason{{=}}#}} for titles containing #
*{{tlx|Correct title|''Correct title''|reason{{=}}bracket}} for titles containing < > [ ] { }
*{{tlx|Correct title|''Correct title''}} for cases not covered by any one of the above. Use {{tn|!}} to represent the | character within the correct title.

Examples:
* '''Song #3''' is located at [[Song 3]]
* '''#Beautiful''' is located at [[Beautiful (Mariah Carey song)]]
* '''''#willpower''''' is located at [[willpower (will.i.am album)|''willpower'' (will.i.am album)]]
* '''''Point #1''''' is located at ''[[Point No. 1]]''
* '''''Look Out for #1''''' is located at ''[[Look Out for Number 1]]''
* '''C# (programming language)''' is located at [[C Sharp (programming language)]]
* '''Cygnus OB2 #12''' is located at [[Cygnus OB2-12]]
* '''''[A→B] Life''''' is located at ''[[(A→B) Life]]''
* '''<|°_°|>''' is located at ''[[Robot Face]]''
* '''''While(1<2)''''' is located at ''[[While(1 Is Less Than 2)]]''
* '''''[title of show]''''' is located at ''[[title of show]]''
* '''''Cat #1''''' is located at [[Cat 1 (album)|''Cat 1'' (album)]]

===Clashes with invalid-UTF-8 handling===
Titles cannot contain invalid [[UTF-8]] sequences (for our purposes, those that would decode to [[UTF-16]] [[Universal Character Set characters#Surrogates|unpaired surrogates]] or code points beyond U+10FFFF). Thus, titles like [https://en.wikipedia.org/wiki/%ED%9F%C0 %ED%9F%C0] (contains a UTF-8 sequence decoding to code point U+D800, an unpaired surrogate) or [https://en.wikipedia.org/wiki/%F6%80%80 %F6%80%80] (contains a UTF-8 sequence decoding to code point U+180000, beyond the U+10FFFF limit) are invalid. (These examples use percent-encoded URLs rather than wikilinks, as the "characters" themselves ''should'' be impossible to insert into wikitext without percent-encoding.)

This also means that three ''valid'' UTF-8 sequences are forbidden in page titles (how these are displayed may vary depending on your browser and installed fonts):

:<code>� � �</code>

The first of these characters or "characters", the [[Specials (Unicode block)#Replacement character|replacement character]], is forbidden because the MediaWiki software uses the replacement character to represent invalid UTF-8 sequences, and cannot differentiate this use as a placeholder from an actual instance of the replacement character. The other two (the two [[Universal Character Set characters#Non-characters|noncharacters]] at the end of [[Plane (Unicode)|Unicode plane]] 0, the [[Plane (Unicode)#Basic Multilingual Plane|Basic Multilingual Plane]]) are forbidden because the MediaWiki software uses the replacement character as a placeholder for these, just as it does for invalid UTF-8 sequences. Note, however, that the other 64 Unicode noncharacters (a block of 32 from U+FDD0 through U+FDEF, plus the two at the end of each of planes 1 through 16 [totaling another 32]) are ''not'' forbidden in page titles, as can be seen in the following examples:

:[[﷐|Noncharacter encoded at U+FDD0]]
:[[􏿾|Noncharacter encoded at U+10FFFE]]

==Other problematic characters==
===Colons===
{{Shortcut|WP:NC-COLON|WP:NC-COLONS}}
In general, article titles containing colons are fine, subject to the following exceptions:
*Page names cannot begin with a colon. However, if the initial colon can be dropped to produce a satisfactory title, then this should be done, and the problem fixed with [[WP:DISPLAYTITLE|DISPLAYTITLE]]. (This will not work with more than one initial colon.). This happens because an initial colon is used for the [[Help:Colon trick|colon trick]].
*Article titles should not begin with a standard [[WP:Namespace|namespace]] prefix ('''Talk:''', '''Help:''' etc.), as this will place them in the wrong namespace, which (among other problems) will exclude them from standard search results. In this case, another title must be found (it won't help to change the capitalization of the prefix or put spaces before or after the colon). For example, '''Help: A Day in the Life''' is located at [[Help!: A Day in the Life]]. A [[WP:Redirect|redirect]] is created at the original title (in this case at [[Help:A Day in the Life]], which is what the above title [[WP:Canonical|resolves]] to).
*Article titles cannot begin with an [[Help:Interwiki linking|interwiki]] or [[Help:Interlanguage links|interlanguage]] prefix, or namespace [[Help:Namespace#Aliases|alias]]. Again, these are case-insensitive, and putting spaces before or after the colon will not help. Examples:
**'''Lad: A Dog''' is located at ''[[Lad, A Dog]]'' ('''lad:''' is the prefix for [[{{#language:lad|en}} Wikipedia]])
**'''DK: Jungle Climber''' is located at ''[[DK Jungle Climber]]'' ('''dk:''' is one of the prefixes for the [[Danish Wikipedia]], the other is '''da:''')
**'''Portal: No Escape''' is located at ''[[Portal – No Escape]]'' ('''Portal:''' is a prefix for [[Wikipedia:Portal|Wikipedia Portal Pages]])
**'''Project: Mersh''' is located at [[Project Mersh]] ('''Project:''' is an alias for the [[Wikipedia:Project namespace|Wikipedia namespace]])
**'''V: The New Mythology Suite''' is located at [[V – The New Mythology Suite]] ('''v:''' is a prefix for [[Wikiversity]])
**'''B: The Beginning''' is located at [[B – The Beginning]] ('''b:''' is a prefix for [[Wikibooks]])
**'''C:Real''' is located at [[C Real (Greek band)]] ('''c:''' is a prefix for [[Wikimedia Commons]])
**'''W:/2016Album/''' is located at ''[[:/2016Album/]]'' ('''w:''' is a prefix for the [[English Wikipedia]]).
:In the case of aliases a redirect can be created. In the third example above this will be at [[Wikipedia:Mersh]], which is what "Project: Mersh" [[WP:Canonical|resolves]] to.

Except in the case of initial colons and the w: and en: prefixes, DISPLAYTITLE will not work in the above situations. Use {{tlp|correct title|''correct title''|reason{{=}}:}}.

===Forward slashes and periods===
{{Shortcut|WP:NC-SLASH}}In [[WP:namespace|namespace]]s where the [[Help:Subpages|subpage feature]] is enabled, the forward slash (/) separates a subpage name from its main page name. However subpages are ''disabled'' in the [[WP:main namespace|main namespace]], so article names can contain slashes if appropriate, as in [[Providence/Stoughton Line]] – there is no need for such titles to be fixed. Be aware of the following side effects, however:
* Subpages are still enabled in the talk namespace as they are widely used for archiving old discussions. Therefore, if an article has a forward slash in its name, its corresponding talk page may display an extraneous subpage level-up link at the top (for example, [[Talk:Providence/Stoughton Line]] has a link to [[Talk:Providence]] at the top).
* If / is the first character of the title, then links to it from outside the main namespace will not work as expected (they will prepend the title of the current page); a workaround is to prepend a colon, or to use an HTML entity as the beginning of the link, e.g. <nowiki>[[:/dev/null]]</nowiki>, <nowiki>[[&#47;dev/null]]</nowiki> or <nowiki>[[&#x2f;dev/null]]</nowiki> to get to [[:/dev/null]].

Page names consisting of exactly one or two periods (full stops), or beginning with '''./''' or '''../''', or containing '''/./''' or '''/../''', or ending with '''/.''' or '''/..''', are not allowed. In most such cases [[WP:DISPLAYTITLE|DISPLAYTITLE]] will not work, so {{tl|correct title}} should be used. As a result of this, the abbreviation of ''[[Slashdot]]'', '''''/.''''', does not redirect to the page.

===Non-printable ASCII characters===
The non-printable characters with values 0 through 31 and the [[delete character]] (127 in ASCII) are also unusable in page titles.

===Percent and encoded characters===
A title can normally contain the character %. However it cannot contain % followed by two [[hexadecimal]] digits (which would cause it to be converted to a single character, by [[percent-encoding]]). Similarly a title cannot contain [[HTML character entities]] such as <code>&#47;</code> and <code>&ndash;</code>, even if the character they represent is allowed. In the unlikely event of such sequences appearing in a desired title, an alternative title must be constructed (for example by inserting a space after the %, or omitting a semicolon).

===Question marks and plus signs===
There is no reason why titles should not include ? or +. However, with such titles, attention is required when typing URLs into the address bar of a browser. Here ? is interpreted as beginning a [[query string]], and a + in a query string is interpreted as a space. When typing in URLs, ? and + should be replaced by their corresponding [[escape code]]s, %3F and %2B. (The same technique is necessary for many other special characters, depending on browser.)

===Semicolons===
Page titles on Wikipedia can only end in a semicolon if there are also one or more semicolons elsewhere in the title (eg. [[exam;ple;]]). This is not a limitation in the MediaWiki software itself, but a problem arising from Wikimedia's caching servers ({{phab|T238285}}). Clicking the link <code>[[;]]</code> will take users to the [[Main Page]] because the semicolon is stripped from the URL. The only way to bypass this is to use full URLs like so: [https://en.wikipedia.org/w/index.php?title=; /w/index.php?title=;], which correctly redirects to the article about the punctuation mark.

===Spaces and underscores===
In [[Help:Link|links]], spaces ({{char| }}) and underscores ({{char|_}}) are treated equivalently. Underscores are used in URLs, spaces in displayed titles. Leading and trailing spaces/underscores are stripped, consecutive spaces/underscores are reduced to a single one, and page names consisting of only spaces and underscores are not allowed at all.

Titles affected by this behavior can generally be made to display correctly using the [[WP:DISPLAYTITLE|DISPLAYTITLE]] magic word. However, this does not work for titles consisting of only spaces and underscores, which should use a parenthetical disambiguator e.g. [[_ (album)|''_'' (album)]] is located at [[(album)]]. Articles with underscores in titles are tracked in [[:Category:Articles with underscores in the title]].

===Three consecutive tildes===
Titles cannot contain three or more consecutive [[tilde]]s (<nowiki>~~~</nowiki>), as four consecutive tildes are used to create standard editors' [[WP:Signatures|signatures]] on talk pages, while three consecutive tildes generates an undated signature.

==Title length==
{{Shortcut|WP:TITLELENGTH}}
Titles must be fewer than 256 bytes long when encoded in [[UTF-8]]. Therefore, the full titles of ''[[The Boy Bands Have Won]]'' and ''[[When the Pawn...]]'' cannot be displayed properly, so they must be located under their common shorthand names.

==Italics and formatting==
It is not possible for a title ''as stored in the database'' to contain formatting, such as italics or bolding. The double or triple apostrophes normally used to produce these effects in wiki markup are treated just as groups of apostrophes if they appear in titles. Other wiki markup or HTML-based formatting would require characters that are not permissible in titles (see [[#Forbidden characters|Forbidden characters]] above).

It is technically possible to ''display'' formatting in titles using [[WP:DISPLAYTITLE|DISPLAYTITLE]]. A template, {{tl|italic title}}, exists to display the title in italics. For guidance on when this technique should be used, see [[WP:ITALICTITLE]].

==Pictorial names==
Titles cannot contain images (which would require forbidden characters in order to be displayed), only [[Unicode]] characters. For example, the recycling symbol [[♲]] is encoded in Unicode as U+2672, so it can be included, but the [[:File:Pictogram NDB.svg|non-directional beacon symbol]] is not a Unicode character and cannot appear in a page title.

==Browser support limitations==
{{see also|Wikipedia:Naming conventions (standard letters with diacritics)#Printability}}
Use [[precomposed character]]s when possible.

Use the [[Unicode normalization|text normalization]] NFC [https://www.w3.org/TR/charmod-norm/].

==Restrictions on usernames==
{{see also|Wikipedia:Username policy}}
Usernames are subject to the same technical restrictions as page titles (see [[#Forbidden characters|Forbidden characters]] above), in particular that the symbols <code># < > [ ] | { }</code> are not allowed. There are also additional restrictions:
* The username must not already exist, including in the [[WP:SUL|single unified login]] system.
* It may not contain the symbols <code>/ @ :</code>.
* It may not contain various control characters, unusual whitespace, or [[UTF-8]] [[private use characters]]: U+0080–U+009F, U+00A0, U+2000–U+200F, U+2028–U+202F, U+3000, or U+E000–U+F8FF.
* It may not be an IP address (including IPv6 such as 2606:4700:4700::1111), nor may it look like an IP address (for example, "564.348.992.800" is not a valid IP address, but since it looks like one, it is an invalid username).
* It may not be one of a list of configured reserved usernames (e.g. "MediaWiki default").
* It may not have a [[WP:namespace|namespace]] or [[WP:interwiki|interwiki]] prefix.
* It may not be more than 85 bytes long.
Additionally, there are the restrictions tested by [[mw:Extension:AntiSpoof|the AntiSpoof extension]], which includes more blacklisted characters (various '/'-lookalikes and characters from unusual scripts such as Runic, Ugaritic, and so on) and checks against mixed scripts. There are also limitations placed by [[meta:Title blacklist]], both the normal blacklisting rules and those tagged by <code><nowiki><newaccountonly></nowiki></code>. Among the more notable of these are that accounts containing strings implying advanced permissions (e.g. "admin") or impersonating high-profile users are blocked.

[[Category:Wikipedia naming conventions|Technical restrictions]]

Wikipedia:Naming conventions (technical restrictions) - Revision history

Tachyony: ←Created page with '{{short description|Project page on technical restrictions for page names}} {{pp-semi-indef|small=yes}} {{redirects here|Wikipedia:Technical restrictions|technic...'