View source for Help:Cache

'''Caching''' is a system for optimizing the performance of websites like the Terraria Wiki. It is implemented both client-side (in the user's internet browser) and server-side (on wiki.gg's servers). Occasionally this caching scheme goes awry, making it necessary to ''bypass'' the cache.

== Server-side cache ==
Constructing a wiki page from its source code consumes processing power on wiki.gg's servers, where this takes place. In order to minimize the consumption, the servers do not build a page every time it is visited by a user. Instead, it is only constructed once, and the result is stored ("cached") and displayed to users. It is then usually only re-built if its source code changes, i.e. after an edit. This can sometimes cause issues, however, e.g. where a page needs to be re-built a second time to display its content correctly.

There are two methods to clear a page's cached version and force a re-build: '''purging''' and '''null-editing'''. Both do not modify any content at all and can be executed safely at any time.

=== Purge ===
A purge often fixes most display problems caused by server-side caching issues. It can be performed in several ways:

* Button: There is a "{{int:cargo-purgecache}}" button in the "{{int:cactions}}" dropdown in the top right of the page. The [[Special:Preferences#mw-prefsection-gadgets|gadgets]] "Purge Link" and "UTC Clock" also provide buttons to purge a page (note that gadgets are only available to logged in users).
* Manually: Modify the URL of the page in question by appending <code>?action=purge</code> (or, if the URL already contains a question mark, <code>&action=purge</code>) and go to that URL.
* Link: Some pages provide a direct link to purge the page (the {{tl|purge}} template can be used to easily implement one).

All of these methods lead to an interface where the purge has to be confirmed by clicking the "OK" button.

=== Null-edit ===
A null-edit, null edit, or blank edit is more "powerful" than a purge. It imitates an actual edit and thus forces a complete re-build of the page, including an update in various listings like categories and [[Special:WhatLinksHere|{{int:whatlinkshere}}]]. It is performed by clicking the "{{int:skin-view-edit}}" (or "Edit source") tab at the top of the page and saving the page ''without making any changes''.

== Local cache ==
{{float file box|style=font-size:100%|width=23em|title=Clearing the browser cache
|Most '''Windows''' and '''Linux''' browsers:
|Hold down {{key|Ctrl}} and press {{key|F5}}.
|title3=<nowiki/>
|'''Apple Safari''':
|Hold down {{key|Shift}} and click the '''Reload''' toolbar button.
|title5=<nowiki/>
|'''Chrome and Firefox for Mac''':
|Hold down {{key|Cmd}} and press {{key|R}}.
}}

To speed things up and conserve communications bandwidth, browsers attempt to keep local copies of pages, images, and other content, so that it need not be downloaded again later. If this causes issues, the browser has to clear a page's cache and re-download its complete, up-to-date content. The browser cache can be cleared using the instructions shown to the right.

Three common problems that can be attributed to browser caching are:
* Images not changing after uploading a new version.
* Item linking template not updating the exclusivity icons.
* [[mw:Extension:Cargo|Cargo]] queries (e.g. on weapon group pages, such as [[Guns]]) missing certain entities.

== Notes ==
* Images at the Terraria Wiki operate on a separate caching system that cannot be updated manually, and no method described on this page will have any effect on them. In order for images to properly update, the caching period must expire on its own, which generally occurs after 5–15 minutes – but can occasionally take even hours.

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