Wikipedia:Naming conventions (technical restrictions)

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"Wikipedia:Technical restrictions" redirects here. For technical restrictions on editing privileges, see Wikipedia:User access levels. For technical restrictions on external links, see WP:Spam blacklist.

Some 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[edit]

Restrictions on page titles are listed at Wikipedia:Page name#Invalid page names. 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 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 {{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 {{correct title}} to place a hatnote stating what the correct title should be. This is normally necessary in the case of restricted characters.

IMPORTANT NOTE: These templates should never be 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.

ANOTHER IMPORTANT NOTE: 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[edit]

The MediaWiki software is configured so that a page title (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. [[foo]] is treated the same as [[Foo]].

Examples of articles affected by this problem are:

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, place the {{lowercase title}} tag at the top of the article page (and optionally at the top of its discussion page). This will cause the article title to be displayed with the initial letter in lowercase, as at eBay. Note that it does not fix every occurrence, like the history, edit, or log pages.

Forbidden characters[edit]

Due to clashes with wikitext and HTML syntax, the following characters can never be used in page titles (nor are they supported by DISPLAYTITLE):

# < > [ ] | { }

For articles about these characters, see number sign, less-than sign, greater-than sign, bracket (covers several characters), vertical bar.

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. Gtk Sharp instead of Gtk#) 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:

  • {{Correct title|Correct title|reason=#}} for titles containing #
  • {{Correct title|Correct title|reason=bracket}} for titles containing < > [ ] { }
  • {{Correct title|Correct title}} for cases not covered by any one of the above. Use {{!}} to represent the | character within the correct title.

Examples:

Other problematic characters[edit]

Forward slashes and periods[edit]

Shortcut:

In namespaces where the subpage feature is enabled, the forward slash (/) separates a subpage name from its main page name. However subpages are disabled in the main namespace, so article names can contain slashes if appropriate – 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 discussion. Therefore if an article has a forward slash in its name, its corresponding talk page may display a redundant subpage level-up link at the top (for example, Talk:R/2004 S 1 had a link to Talk:R at the top before it became a redirect).
  • 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 a html entity as the beginning of the link, e.g. [[:/dev/null]], [[&#47;dev/null]] or [[&#x2f;dev/null]] 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 DISPLAYTITLE will not work, so {{correct title}} should be used. As a result of this, the abbreviation of Slashdot, /., does not redirect to the page.

Spaces and underscores[edit]

In links, spaces ( ) and underscores (_) 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/underscores are not allowed at all.

Titles affected by this behavior (except for the last restriction) can generally be made to display correctly using the DISPLAYTITLE magic word.

Colons[edit]

In general, article titles containing colons are fine, subject to the following exceptions:

In the case of aliases a redirect can be created. In the fourth example above this will be at Wikipedia:Mersh, which is what "Project: Mersh" resolves to.


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

Percent and encoded characters[edit]

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 &#47; and &ndash;, 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[edit]

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 codes, %3F and %2B. (The same technique is necessary for many other special characters, depending on browser.)

Three consecutive tildes[edit]

Titles cannot contain 3 or more consecutive tildes (~~~), as strings of tildes are used to create editors' signatures on talk pages.

Title length[edit]

Titles must be less than 256 bytes long when encoded in UTF-8.

Italics and formatting[edit]

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 wikitext are treated just as groups of apostrophes if they appear in titles. Other wikitext or HTML-based formatting would require characters that are not permissible in titles (see Forbidden characters above).

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

Pictorial names[edit]

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 Armenian eternity sign ArmenianEternity.svg found in ArmSCII is not a Unicode character and so cannot appear in a page title.

Browser support limitations[edit]

See also: Wikipedia:Naming conventions (standard letters with diacritics)#Printability

Use precomposed characters when possible.

Use the text normalization NFC [1].

Restrictions on usernames[edit]

Usernames are subject to the same technical restrictions as page titles (see Forbidden characters above), in particular that the symbols # < > [ ] | { } are not allowed. There are also additional restrictions:

  • The username must not already exist, including in the single unified login system.
  • It may not contain the / character.
  • 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 contain '@' (unless $wgInvalidUsernameCharacters is changed).
  • It may not be an IP address.
  • It may not be one of a list of configured reserved usernames (e.g. "MediaWiki default").
  • It may not have a namespace or interwiki prefix.
  • It may not be more than 235 characters long (in practice the limit is 40 characters; see below).

Additionally there are the restrictions tested by mw:Extension:AntiSpoof, 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 and MediaWiki:Titleblacklist, both the normal blacklisting rules and those tagged <newaccountonly>. Among the more notable of these are that accounts containing strings implying advanced permissions (e.g. "admin") or impersonating high-profile users are blocked, and the maximum username length is reduced to 40 characters.