A Wikipedia namespace is a set of Wikipedia pages whose names begin with a particular reserved word recognized by the MediaWiki software (followed by a colon). For example, in the user namespace all titles begin with the prefix User:. In the case of the article (or main) namespace, in which encyclopedia articles appear, the reserved word and colon are absent. (Note: main space articles can optionally include a colon at the beginning with no reserved word, so
[[:Article]] are equivalent. This is usually only necessary for the advanced technique of transcluding a main space article into another page.)
Wikipedia has 30 current namespaces: 14 subject namespaces, 14 corresponding talk namespaces, and 2 virtual namespaces. These are all listed in the box to the right. While surfing Wikipedia, a list of namespaces is available in two clicks: do an empty search, then click Advanced under the search box. The list also makes itself available where needed in the dropdown menus of, for example, Special:Prefixindex, Special:Allpages, Special:Recentchanges, and Special:Contributions.
The aliases WP for Wikipedia, and WT for Wikipedia talk, work for page names in the search box, and making links as well as inclusions. See Aliases below for other aliases. (The pseudo-namespaces such as H for Help, and CAT for Category, are extremely limited. See Pseudo-namespaces below.)
The table on the right shows what number to use when you want to hide pages that are on your watchlist. See: Wikipedia:Hide Pages in Watchlist for details.
Previously, the Topic namespace was available for the Flow project but it has since been turned off on this wiki.
Namespaces allow for the organization and separation of content pages from administration pages. Namespaces separate data into core sets, those intended for public viewing, and those intended for the editing community. Wikipedia's subject namespaces and their functions are listed below. A brief description is provided, but see the link for more information.
A namespace is sometimes called a space, for short, as in "Project space". A subject page and its talk page form a pair.
On MediaWiki installations other than the English Wikipedia, additional namespaces may be installed by MediaWiki extensions; the list of default IDs for these namespaces is at Extension default namespaces.
An alias of a namespace is its namespace. For example, WP: is Wikipedia:, and so
[[Wikipedia:Page name]] can be abbreviated
See Aliases below, for a list of aliases, such as WT: for Wikipedia talk:.
A pseudo-namespace is an agreement to create redirect pages named that way, each of which
is a shortcut from mainspace to a single page in its namespace.
So an alias refers to any page in its namespace, but a pseudo-namespace has far fewer pages than its real namespace.
There are a few pseudo-namespace names like H: for Help:, and CAT: for Category:, and these can be discovered below in the section Pseudo-namespaces.
Each of the above namespaces (but not the virtual namespaces and the former Topic: namespace) has an associated talk namespace—these are also known as discussion pages. The talk namespaces are designated by appending the word
talk to the namespace name. For example, the talk namespace associated with the user namespace has the prefix User talk:. The talk namespace associated with the article namespace is Talk:.
Most of the pages in the talk namespaces are used to discuss changes to the corresponding page in the associated namespace. Pages in the user talk namespace are used to leave messages for a particular user. The user talk namespace is special in that, whenever a user's talk page is edited, that user will see an orange box saying "You have new messages" on the top of every page that they view until they visit their talk page. By default, logged-in users will see a red notification square and a small orange box on the top right hand corner of the page; IP users will only see a wide orange box spanning the top of the page. (Minor edits made by bots no longer set off the new message bar. For logged-in users, the new-message bar may be disabled in Special:Preferences.)
In addition to subject namespaces, and their corresponding talk pages, there are two virtual namespaces (without corresponding talk pages) for specialist purposes:
The Special: namespace consists of pages (called special pages) that are created by the software on demand, such as Special:RecentChanges. These pages can be linked as usual, as with [[Special:RecentChanges]], except when they have parameters. To use parameters, the full URL must be given as an external link. For example, , which returns the last ten changes in the last three days.
You can create a redirect to a Special page, but the redirect will not be followed automatically.
The Media: namespace can be used to link directly to a file, rather than to the file description page.
Aliases and pseudo-namespaces are not namespaces in themselves; their main role is to provide handy ways to link to actual namespaces, by providing shortened links.
The main difference between them being the way they work for this purpose; while aliases directly link to namespaces, pseudo-namespaces can only link to other namespaces by using specialist redirect pages in the main namespace called shortcuts. While aliases are also used for shortcuts, this isn't necessary if the pagename is not shortened.
Pseudo-namespaces all actually reside in main namespace; but a pseudo-namespace called Transwiki: exists as a pseudo-namespace before being moved to another namespace.
There are six aliases defined for namespaces, all of which are case-insensitive:
These aliases are automatically translated by the Wikipedia servers to the proper namespace prefix. So if a link is made to a page title beginning with one of these aliases, or else entered in the search box or used in a URL in a browser address bar, the alias links to the page with the corresponding true namespace prefix. Hence entering WP:External links or Project:External links is equivalent to entering Wikipedia:External links; and entering WT:External links or Project talk:External links is equivalent to entering Wikipedia talk:External links.
An alias cannot be used as the actual namespace in a page title. For example, you cannot create page WP:123; if tried, the page name is instantly converted to Wikipedia:123. It is, however, possible to change the displayed title on page Wikipedia:123 to make it WP:123 or Project:123.
Apart from Wikipedia's 32 regular namespaces and their aliases, and 2 virtual ones, there are several title prefixes appearing in shortcut redirects pointing to frequently-referred-to Wikipedia pages. These prefixes are referred to as pseudo-namespaces and include the following:
A more complete list is available at Wikipedia:Shortcut#List of prefixes.
Pseudo-namespaces are not in any way recognised by the wiki software; they are purely a community custom. Titles in pseudo-namespaces actually belong technically in the main (article) namespace and are treated as such by the software: they are case-sensitive and appear in search results restricted to the main namespace. An alias is treated like a real namespace, resulting in a search for the pagename in its namespace, but the "pseudo-namespace:pagename" search is in mainspace, not its pseudo-namespace. For example, searching for "H:S" will not search Help.
To understand the appropriateness of redirects of this type, see Wikipedia:Cross-namespace redirects. All shortcuts are discoverable by searching for redirects. There is also the category Wikipedia redirects.
As a final example, every Wikimedia Foundation project has a "Transwiki:" pseudo-namespace (sometimes a real namespace) for importing articles manually. A wiki project that would manually move many pages between sister projects uses this tag. Redirects/shortcuts are not directly involved here, as described above. Instead, the page title is moved to "Transwiki:namespace:pagename", and that content is then copied and pasted into a new page name of that temporary title on the target wiki. When it is accepted, the title is then moved out of the Transwiki pseudo-namespace there and becomes a real page name in its respective namespace.
Interwiki and interlanguage prefixes do not define namespaces, but point to pages in other Wikimedia projects, outside the en.wikipedia.org website. They are mentioned here because they use a namespace-like prefix technique for linking. Examples of interwiki prefixes include w: for Wikipedia; m: (or meta:) for Meta-Wiki, mw: for MediaWiki, and wikt: for Wiktionary. Examples of interlanguage prefixes include en: for English language, fr: for French language, and de: for German language.
When making links to other language Wikipedias, add an initial colon if you want the link to appear inline rather than in the skin's sidebar under "Languages"; see Help:Colon trick for an explanation. So
[[:de:Internet]] is an inline link to "Internet" in the German Wikipedia; but if using an interwiki prefix this is unnecessary, for example
[[w:de:Internet]] is the same inline link.
Interwiki prefixes are not just for Wikimedia projects. For example, Dictionary: is the interwiki link for dict.org (the DICT Development Group). For a complete list of interwiki prefixes, see the interwiki map and interwiki table.
As with aliases, it is not possible to create a page with a title beginning with an interwiki or interlanguage prefix. It is also not possible to create redirects to interwiki pages, unless it is a soft redirect.
Standard namespace names, aliases and interwiki prefixes are case insensitive. The same applies to the first character after the colon. Hence the following all link to the same page:
The namespace name is a useful variable for searching in and reporting on sets of pages. It is also used to apply features that configure the sets of pages in one namespace differently from another namespace. Using the namespace name MediaWiki can:
The namespace functionality is often visible in the URL, where you will see a namespace number. These are given in the table below.
Subpages are configured for all namespaces except Main, File, MediaWiki and Category namespaces. Subpages are configured in the software by enabling or disabling the subpage feature per namespace. This further extends the function of a namespace by extending the types of pages or topics of pages a namespace can home. For example, talk page /archives are subpages, and they are both namespace searchable and page name searchable from the search box, unlike history pages, which are in no namespace. Another example is in the Template namespace where it is routine to put the documentation in a subpage called /doc.
Random pages are enabled, in the default software configuration, only for the mainspace.
Searching and reporting can operate over the entire database, or they can be limited to a namespace, and so they will offer a list of all the namespaces currently configured. Special:WhatLinksHere also offers a list of namespaces.
All namespaces with a positive number or zero in this list are searchable. Specifically, the Media and Special namespaces are not searchable.
For information on changing the appearance of a page or template by namespace based on CSS, see CSS-based namespace detection on the Meta help page.