Manual:Parser cache

The parser cache is responsible for caching the rendered output of a wiki page. It is (in the absence of a web-cache layer in front of MediaWiki) the primary caching mechanism for serving page views in MediaWiki.

See also:
 * The case is split (varied) based on ParserOptions. This uses a two-tiered system
 * The Parser cache is semi-permanent. A ParserCache based on "canonical" ParserOptions entry is pre-generated upon save, and re-generated using the LinksUpdate mechanism.
 * Parser cache entries can be invalidated individually by bumping the page_touched field, or collectively by bumping the $wgCacheEpoch setting.
 * The cache includes meta-data extracted by core and defined by extensions
 * Since 1.36, the cache uses JSON serialization. Before that, it relied on PHP serialization.
 * Since 1.36, it is possible to have multiple ParserCache instances side by side. ParserCache instances are managed by the ParserCacheFactory which can be obtained from MediaWikiServices.
 * The main ParserCache covers the latest revision of a page. Since 1.36, a similar cache exists for old revisions of a page, the RevisionOutputCache. Instances of RevisionOutputCache are managed by the ParserCacheFactory which can be obtained from MediaWikiServices. The intent of RevisionOutputCache is to protect against load spikes caused by certain old revisions of a page being viewed by a large number of users, typically due to an external "deep" link to that revision. As such, this cache is usually configured with a short expiry time (per default, one hour), and typically have a low it rate.
 * Configuration: ...


 * Parser_cache for the parser cache configuration used on the Wikimedia cluster
 * Manual:Object cache
 * Manual:Architectural modules/Cache
 * Manual:Configuration_settings