Community Central
Community Central

Creating some custom code for your community or for your own account? This page goes a little further than our overview page to give you some helpful details.

Before you get started, though, you'll want to check out which pages can be used for customization. If you're planning to write some JavaScript for your community, you'll need to ask for it to be turned on by contacting Fandom Support, and familiarize yourself with the JavaScript review process.

Page-specific customization[]


The <body> HTML element on articles includes a unique identifier based on the name of the page. For example, on this help page, the class is .page-Help_Advanced_CSS_and_JS

The general format is .page-[article name], where spaces, colons, and other special characters are replaced by underscores.


In MediaWiki:Common.js, use a switch to apply JavaScript to certain pages:

switch (mw.config.get('wgPageName')) {
    case 'page name':
        // JS here will be applied to "page name"
    case 'some other page':
        // JS here will be applied to "some other page"

Applying CSS and JS to specific communities[]

In your personal CSS, you can add a class to the front of any other CSS selectors that will let you style the way your account looks at specific wikis.

This class is based on the database name of a community, not the URL — which are usually, but not always, the same. The format is:

.wiki-[database name]

or, if a non-English wiki:

.wiki-[language code][database name]

For instance, if you wanted to make part of the background of Wookieepedia appear red to you, add this to your global.css file:

.wiki-starwars #WikiaMainContent { background-color:red; }

For JavaScript, wgDBname can be used to identify a specific community.

Load order[]

The general load order for both CSS and JS is:

  1. Fandom's core code
  2. local community code
  3. personal code

Within each level, the load order is Common first, then Fandomdesktop. This means that if you've said .class { color: red; } in Common.css, but .class { color: green; } in Fandomdesktop.css, the .class will be green. And because personal CSS is last, whatever you put there always overrides the local wiki's choices.

It also critically means that if you're importing CSS or fonts — and your wiki has both Common.css and Fandomdesktop.css — those imports need to be at the very top of Common.css.

For JS, load order is especially important when considering how to best use MediaWiki:ImportJS. Because ImportJS loads last, you can put your customization of a Dev Wiki script in Common.js or Fandomdesktop.js, but have the import of the script itself in ImportJS. The full JS load order is:

  1. Common.js
  2. Fandomdesktop.js
  3. Imported scripts through Common.js
  4. Imported scripts through Fandomdesktop.js
  5. ImportJS

Finally, remember the obvious: pages load from top to bottom. That means that declarations made at the top of a page can be overridden by ones at the bottom.

!important in CSS[]

Due to CSS load orders, you may sometimes need to make use of the !important property to ensure a CSS rule is applied. But !important should be avoided when possible by use of specific (even overly specific) CSS selectors.

Caching issues[]

Every file you download from the internet gets cached. Normally that's great because it reduces traffic both for your own device and for Fandom's servers, but it can be a problem when it comes to testing design changes. It may take a while before your changes to take effect unless you bypass your cache.

If bypassing your cache doesn't work, you can try debugging your code by adding ?debug=1 at the end of the URL of any page. Debugging your code means that the code will almost 100% guarantee the load of the recently added script(s) and/or stylesheet(s).

Popular JavaScript snippets[]

To get an idea of some scripts others have written that you might find useful or would like to try, take a look at the list of JS Enhancements on the Fandom Developers Wiki.

Duplicate JavaScript[]

Many scripts can have problems if they are run multiple times on the same page. Make sure to write the code in such a fashion that a particular piece of code runs only once. Avoid pasting the same JS in multiple files as it will likely conflict and cause confusing errors for you and other visitors.

Temporarily disabling CSS/JS[]

Custom CSS and JS can be temporarily disabled using the following commands.

The command(s) should be added at the end of the URL (example: [The following example disables site CSS]).

If more than one command is needed, instead of question mark (?), put an ampersand (&) for the second, third and fourth commands (in case if there are) (example: [The following example disables site CSS and personal JS]).

Here's a table of all the CSS/JS commands.

Command Role
?useusercss=0 Disables all CSS that was added into your personal CSS pages.
?useuserjs=0 Disables all JS that was added into your personal JS pages.
?usesitecss=0 Disables all CSS that was added into the wiki's locally-defined CSS.
?usesitejs=0 Disables all JS that was added into the wiki's locally-defined JS.
?safemode=1 Disable all custom CSS and JS, sitewide and personal.

CSS and JS editor error checking[]

The CSS and JS editors have active error checking ("linting") and syntax highlighting:

  • As you type code, the page will let you know about any errors in the syntax that might have occurred.
  • Note that not every flagged issue has to be solved; CSS (and even JS) technology is ever evolving, and browsers do not all behave identically: some messages may not require action.

Common issues[]

CSS issues
Issue Explanation
@import prevents parallel downloads, use <link> instead Link tags are normally used to import CSS. However, MediaWiki does not support adding your own link tags without use of JS, so this error can normally be ignored. Using @import is the preferred method.
Expected X but found Y This means you have entered an invalid value for a property. For example, in color: foo; foo is an invalid value for the color property because it is not a color. This may be sometimes a false positive, as sometimes it doesn't accept unset or etc as valid values.
Use of !important !important should generally be avoided in CSS as it can make it harder to maintain, and also makes it harder for users to override settings in their personal CSS. Most of the time, using the correct and specific selector will help you avoid using !important.
Unknown property 'codename' Although not all CSS code is recognized by the tool (as CSS itself is a frequently updated artform), certain CSS codes can still be read when they are implemented for a certain object on the page (For example, mix-blend-mode: color-dodge;).
Expected (<color> | inherit) but found 'var(--theme-accent-color)'. This is often shown when using CSS Variables to color borders, backgrounds, and other HTML tags. CSS Lint, which CodeEditor uses for CSS syntax error checking, does not yet support usage of variables.[1] This error can be safely ignored.
Error: Expected RBRACE at line 4, col 5. Again, this will happen if you are using CSS variables. Since CSS Lint doesn't support them yet, the -- preceeding the variable definition will make it throw that error. Note: Saving will show an annoying prompt:
The document contains errors. Are you sure you want to publish?

You can safely ignore this error and press OK, or disable syntax highlighting to stop the error altogether.

See also[]


  1. CodeEditor uses Ace as it's editor. Ace uses CSS Lint for CSS error checking, in which CSS Variables are not supported yet as detailed in this GitHub issue.

Further help and feedback[]