Help:Namespaces and User Rights
Pages on a MediaWiki wiki are grouped into collections called "namespaces", which differentiate between the purpose of the pages at a high level. Pages in certain namespaces can also have special properties or behave differently when they interact with other pages.
Namespaces are indicated in page titles by prefixing the page name with "namespace:", so the prefix "Help:" in this page's title ("Help:Namespaces and User Rights") indicates that this page is in the Help namespace. Note, however, that colons and prefixes can also appear in page titles without indicating a namespace: The page Foo:Namespaces and User Rights is a page located in the mainspace because the namespace "Foo" does not exist. Similarly the page Help:Foo:Namespaces and User Rights is in the "Help" namespace.
Contents
Standard namespaces
The standard MediaWiki installation has sixteen namespaces which can contain user-generated content; there are also two special namespaces which contain pages created 'on the fly' by the MediaWiki software. The standard namespaces are organised in pairs, with each pair containing a 'subject namespace' and a 'discussion namespace'. The namespaces are numbered from zero such that all subject namespaces have even indices, and all talk namespaces have odd indices.
-2: Media
This namespace is an alias used for direct linking to media files: the link Media:Wiki.png links to just the image rather than the image description page, which would be File:Wiki.png.
-1: Special
This namespace is used to group special pages, reports and interfaces that are generated 'on demand' by MediaWiki and which are not directly editable. It is not possible to create pages in this namespace except by modifying or extending the MediaWiki software.
0: (Main)
Namespace zero is the 'null' namespace, commonly called the "main namespace" or "mainspace". This namespace typically contains the bulk of the content pages in a wiki. This namespace generally has no special properties.
2: User
Each user has a corresponding page in the User namespace, which is linked to from edit histories, watchlists, recent changes, etc; wherever an individual user is uniquely identified. This page, and subpages of it, can be used by users to record information about themselves or to test and draft new content. Pages of the form "User:UserName/Foo.js" or "User:UserName/Foo.css" can only be edited by the user themselves or by administrators.
4: SoftMC-Wiki
This is a content namespace that is normally used for meta-discussions related to the operation and development of the wiki. It has no special properties.
6: File
The File namespace is used to store metadata for images, videos, sound files and other media accessed via the Media namespace. Each file has a corresponding page in the File namespace which is often used to hold licensing data. Linking directly to a page in this namespace instead includes the media file inline in the page: [[File:Wiki.png|right]] produces the image to the right. See Help:Images for more details of this link syntax. To create an internal link to the file page, you need to add a colon to the front of the namespace: [[:File:Wiki.png|right]] produces File:Wiki.png. The standard MediaWiki installation has alias "Image" for File namespace - See Namespace aliases.
8: MediaWiki
The MediaWiki namespace is used to hold system messages and other important content. For instance, the page MediaWiki:Edit contains the text that fills the "Edit" tab at the top of every page. If that page exists, it overrides the default content, which is "edit this page". Similarly, MediaWiki:Common.css is the system message which holds the CSS code that is loaded for all users for each page. It has the special property that the entire namespace is fully protected and can only be edited by administrators.
10: Template
The Template namespace is used to hold templates, blocks of text or wikicode that are intended to be transcluded in several other pages. To facilitate this it has the special property that it is the default namespace for transclusions: the wikicode {{Foo}} is equivalent to {{Template:Foo}}.
12: Help
The Help namespace is usually used to hold help files, instructions and 'how-to' guides. It has no special properties.
14: Category
The Category namespace contains categories, dynamic lists of other pages. To facilitate this, linking directly to a category page does not output an inline link, but instead includes the page into the associated category page. So the code [[Category:Help]] causes a category link to appear at the bottom of the page (at the bottom in the box marked "Categories"). Clicking on that link takes you to the category page, where this page is visible in the category list. To create an inline link to a category page, you need to add a colon to the front of the namespace: [[:Category:Help]] produces Category:Help. See Help:Categories for more details on category link syntax.
Custom namespaces
Some wikis may wish to organise their content in ways that do not fit into this standard set of namespaces. A wiki may define additional namespaces to facilitate this; these namespaces behave exactly like normal namespaces, and generally have indices greater than or equal to 100. These custom namespaces generally have no special properties.