Manual:$wgNamespaceContentModels

Content Models and Handlers
MediaWiki allows for page content types other than wikitext. It offers built-in support for JavaScript, CSS, JSON and plain text. Extensions can use MediaWiki's ContentHandler mechanism to add new content models for accepting different formats and controlling how they are rendered, stored and edited.
About
About the ContentHandler Content handlers and their implementation
Usage
Changing the content model of a page Changing the content model of a namespace Extensions using the ContentHandler Adding content models with an extension Examples: includes (part of Examples ) Markdown
Configuration settings
$wgContentHandlers $wgNamespaceContentModels $wgContentHandlerTextFallback $wgContentHandlerUseDB
Support and development Latest technical documentation (Git) Phabricator

Content handlers and storage: $wgNamespaceContentModels
Content types defined for a given namespace
Introduced in version:	1.21.0
Removed in version:	Still in use
Allowed values:	Unspecified
Default value:	[]
Other settings: Alphabetical | By function

Details

Associative array mapping namespace IDs to the name of the content model pages in that namespace should have by default (use the CONTENT_MODEL_XXX constants). If no special content type is defined for a given namespace, pages in that namespace will use the CONTENT_MODEL_WIKITEXT (except for the special case of JavaScript and CSS pages).

Example

JSON

Suppose you have created a new custom namespace NS_JSON and you want all new pages in this namespace to have JSON content and to be supported by the appropriate content handler. Add the following to your LocalSettings.php file.

$wgNamespaceContentModels[NS_JSON] = CONTENT_MODEL_JSON;

If you already created pages in this namespace, see the talk page.