Page name

# Overview
The canonical form of a full page name is shown in large font as the page header. Another type of canonical form is what is in URLs generated by the system, for this page "Help:Page_name" with an underscore. Alternative names for this page (on most projects) are help:page name, help:Page name, Help:page name and Help:Page name, but not Help:Page Name; the alternative names for this page on this project are the bolded ones. For details, see below.

# Terms
The terms "full page name" and "full pagename" include the namespace prefix; the terms "page name" and "pagename" are somewhat ambiguous for pages outside the main namespace as they may or may not include the namespace prefix. To avoid ambiguity one can use "full pagename" and "pagename without namespace prefix".

# Restrictions

## Special characters
The following characters (the configuration is made in "$wgLegalTitleChars") are not allowed in page titles:
The non-printable characters with values 0 through 31, and the "delete" character 127, are also not allowed.
The reasons for disallowing these characters include:
- , {, }, and | have special meaning within Wikipedia's syntax, which are processed before the pagename is determined. For example, ] points at 2023, not a page called {{CURRENTYEAR}}.
In the default setup for MediaWiki, the + character is also not allowed in page titles.  This can be added to $wgLegalTitleChars with
in LocalSettings.php
See also w:en:Wikipedia:Naming conventions (technical restrictions), and the {{DISPLAYTITLE}} magic word.

## Forward slash (/)
Depending on the namespace and the settings, a forward slash in the pagename provides special functionality: see subpage feature.

## Namespace prefixes
Also, the first part of a page name may not coincide with a project-independent namespace prefix that is automatically converted to another one. As an example, the name Project: A-Kon on Wikipedia is not possible.
The first part of a page name can coincide with a namespace prefix that is not converted. For example, there might be articles in the English Wikipedia about books called Wikipedia: The Big Adventure and Talk: Secrets are Bad (but only without the space after the colon). However, in that case the pages are in the wrong namespace.  This may be inconvenient in searching or displaying a list of pages. Also, in the second case there is no link to a Talk page about the book. (As explained above, the second page name is not possible on e.g. the German Wikipedia: see w:de:Talk: Secrets are Bad).
--24.80.210.247 03:18, 5 March 2006 (UTC)--24.80.210.247 03:18, 5 March 2006 (UTC)

## Prefixes referring to other projects or pseudo-namespaces
A page name cannot start with a prefix that is in use to  refer to another project, including language codes, e.g. "en:" (list), or one of the pseudo-namespaces "Media:" and "Special:".
Thus e.g. an article about the album "Q: Are We Not Men? A: We Are Devo!" can not have that exact name. An attempt to create the article, whether by a link Q: Are We Not Men? A: We Are Devo! or a URL :Are_We_Not_Men%3F_A:_We_Are_Devo%21 leads to Wikiquote.
With regard to using the prefix of the project itself there is no consistency: a name like en:a cannot be used on en: (try w:en:a and w:en:en:a), while "Q: Are We Not Men? A: We Are Devo!" can exist on Wikiquote: q:Q: Are We Not Men? A: We Are Devo!.

## Maximum page name length
The maximum page name length is 255 bytes (excluding the namespace prefix). Be aware that non-ASCII characters may take up to four bytes in UTF-8 encoding, so the total number of characters you can fit into a title may be less than 255 depending on the language it's in.
See 
Test of maximum page name length: 255 characters; test of maximum page name length: 255 characters; test of maximum page name length: 255 characters; test of maximum page name length: 255 characters; test of maximum page name length: 255 characters; test.

# Spaces vs. underscores
In page names, a blank space is equivalent with an underscore. A blank space is displayed in the large font title at the top of the page, the URLs show an underscore. See also below.

# Case-sensitivity
If for the first letter of a page name two cases exist, as in the case of letters of the Latin, Greek, Cyrillic, and Armenian alphabets, the following applies.
All characters of namespace prefixes are case-insensitive. The canonical form, shown in  large font as page header, and in URLs generated by the system, is on most projects with one capital; Klingon is an exception, see w:tlh:Chen'ay':h:h, where the c is converted to lower-case, and w:tlh:Qah:Page name, where the h is converted to upper-case. Below "page name" refers to the name without the possible namespace prefix.

## Case-sensitivity of the first character
The first character of the page name (after the namespace prefix, if applicable) may or may not be case-sensitive, depending on the project (see mw:Manual:$wgCapitalLinks). ] gives on this project: Help:page name. If the first character of the page name is case-sensitive this is a link (to a different page), otherwise it is bold (a self link to this page).
On Wikimedia projects currently the first character of the page name is case-insensitive, except in all Wiktionaries.
Compare e.g. wikt:de:A and wikt:de:a.

### Case where the first character is case-insensitive
The canonical form is with a capital.
Note that in the case of a prefix that is not a namespace for the software, and in the case of a second prefix, the case-insensitivity does not apply to the first character after this prefix, e.g. Template:H:h Help and Template:H:H Help are distinguished.

## Case-sensitivity of the file name extension of an image
Note that even the file name extension of an image is case-sensitive: compare image:Stop_sign_us.jpg and   image:Stop_sign_us.JPG

# Ignored spaces/underscores
Spaces/underscores which are  ignored:
- those at the start and end of a full page name
- those at the end of a namespace prefix, before the colon
- those after the colon of the namespace prefix
- duplicate consecutive spaces
Some show up in the link label, e.g. ] becomes ___help__ :_ _template_ _, linking to Help:Template.
However, a space before or after a "normal" colon makes a difference, e.g. MediaWiki User's Guide: Editing overview and MediaWiki User's Guide : Editing overview, and MediaWiki User's Guide:Editing overview are all distinguished, because "MediaWiki User's Guide:" is a pseudo-namespace, not a real one.

# Coding of characters
A page name cannot contain e.g. %41, because that is automatically converted to the character A, for which %41 is the code. ] is rendered as A. Similarly %C3%80 is automatically converted to the character A. ] is rendered as A. The URL of the page is . One can argue what is the real name of the page, %C3%80 or A (a user will say the latter), but anyway there can not be distinct pages with these names.

# Canonical form
The inclusion tag for a non-existing page shows a link with the canonical form of the page name: {{qwsazx}}, {{:qwsazx}}, {{project:qws   azx}} give Template:Qwsazx, Qwsazx, wikidoc:Qws azx; compare with ordinary links Template:qwsazx, qwsazx, project:qws   azx; these work like Piped links, e.g. ]; in this case the conversion shows up on the referring page only when pointing at it: in the pop-up and in the status bar (if applicable for the browser); whether the target is a  redirect, and what the final target is, is not shown at all.
An attempt to include a page from another project results in just displaying the wikitext, e.g. {{en:qwsazx}};  ordinary interwiki links do not show existence and do not show a canonical form in the hover box or status bar:. The same applies if interwiki link style is used for a link to a page in the same project: m:project:qwsazx.
A saved redirect page shows the canonical form of the target, even though the preview renders the link in the usual way, compare  with the preview of .
Help:Alphabetic order

# Conversion of spaces to underscores etc.
There is no feature for just conversion of spaces to underscores and of special characters to escape codes, but there are two features for doing this in combination with something else: localurl (see Help:Variable) and PAGENAMEE.
Most needs for conversion are covered by these, but e.g. in a template one cannot link to a page with a given name {{{1}}} on a project with a different $wgScript.

## Variables PAGENAME and PAGENAMEE
The variable {{PAGENAME}} gives, for this page, Page name. {{PAGENAMEE}} gives Page_name.
Thus in the first case a space is used, in the second case an underscore, like in URLs. Similarly, A becomes the escape code %C3%80 (see above), and so on.
Example:
:Whatlinkshere&target={{NAMESPACE}}:{{PAGENAMEE}}
gives
:Whatlinkshere&target=:Page_name
Within localurl, {{PAGENAME}} should be used in the first part (because it is converted by localurl), or {{PAGENAMEE}} in the second part:
- {{fullurl:Special:Allpages|namespace=12&from={{PAGENAMEE}}}} gives here:
:Allpages&namespace=12&from=Page_name
- {{fullurl:Special:Allpages/{{PAGENAME}}|namespace=12}} gives here:
:Allpages/Page_name&namespace=12
Wrong:
- {{fullurl:Special:Allpages|namespace=12&from={{PAGENAME}}}} gives here:
:Allpages&namespace=12&from=Page name (wrong link)
- {{fullurl:Special:Allpages/{{PAGENAMEE}}|namespace=12}} gives here:
:Allpages/Page_name&namespace=12 (works here, the underscore, converted from a space, is not affected by the second conversion, but it does not work with special characters).