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Over time, MediaWiki core JavaScript functions and HTML outputs have improved in functionality, introduced new methods, been deprecated, or changed in other ways. This document intends to highlight the most common problems that need to be fixed.

  • For an overview of the modules that are available in MediaWiki core, see ResourceLoader/Core modules .
  • Problems with gadgets? Check if it's listed below. If so, ask an interface administrator to update it on your wiki.


The jquery.cookie module provides an API to read and write raw browser cookies via $.cookie. This functionality has been merged into the mediawiki.cookie module.

The jquery.cookie module name is now a deprecated alias for mediawiki.cookie. The module name alias was removed in MediaWiki 1.42.

Both $.cookie and mw.cookie are now provided directly by the mediawiki.cookie module.


The jquery.hoverIntent module provides a helper method to run some code after an element was hovered for a minimum period of time. It does this by delaying your callback, such that very brief of accidental hovers don't cause a potentially "unintended" visual effect. This module is now deprecated (T311194).

There are two migration paths:

  1. Use the built-in jQuery on() function instead (with events mouseenter and mouseleave), or
  2. Re-create a similar effect using setTimeout.

Firstly, consider whether you still need the hoverIntent logic. When we introduced hoverIntent in 2010 (with MediaWiki 1.16 ), there are a number of notable differences compared to today. Mobile was much less significant for gadgets and user scripts, the design and behaviour expectations were different, and performance was balanced based on different trade-offs between CPU and network cost than today. Try converting to the built-in on() and interact with your gadget.


var $btn = $( '.tpl-mybutton' );

// Old code (deprecated)
$btn.hoverIntent( function () {
    $btn.addClass( 'tpl-my-button--active' );
}, function () {
    $btn.removeClass( 'tpl-my-button--active' );
} );

// Old code (deprecated)
$btn.hoverIntent( {
    interval: 300,
    over: function () {
        $btn.addClass( 'tpl-my-button--active' );
    out: function () {
        $btn.removeClass( 'tpl-my-button--active' );
} );

// New code, with on()
    .on( 'mouseenter', function () {
        $btn.addClass( 'tpl-my-button--active' );
    } )
    .on( 'mouseleave', function () {
        $btn.removeClass( 'tpl-my-button--active' );
    } );

Does it get better without the delay? If you prefer to keep the previous behaviour, you can create a similar delaying effect with a setTimeout call and two local varables:

var pending, done;
    .on( 'mouseenter', function () {
        if ( pending ) {
        pending = setTimeout( function () {
            $btn.addClass( 'tpl-mybutton--active' );
            done = true;
        }, 300 ); // delay
    } )
	.on( 'mouseleave', function () {
        if ( done ) {
            $btn.removeClass( 'tpl-mybutton--active' );
        clearTimeout( pending );
        pending = done = null;
    } );

To compare the examples side-by-side refer to https://codepen.io/Krinkle/pen/VwGWgqN.


The jquery.jStorage module was deprecated in 2016 (MediaWiki 1.28). It has been removed in 2021 (MediaWiki 1.38). Use mw.storage from the mediawiki.storage module instead (T143034). See also: mw.storage

// Old (deprecated)
$.jStorage.set( 'mygadget-example', simple ); // simple = 'Hello'
$.jStorage.set( 'mygadget-example', object ); // object = { sub: 'Hello' }

simple = $.jStorage.get( 'mygadget-example' );
object = $.jStorage.get( 'mygadget-example' );

// New (replacement)
mw.storage.set( 'mygadget-example', simple );       // simple = 'Hello'
mw.storage.setObject( 'mygadget-example', object ); // object = { sub: 'Hello' }

simple = mw.storage.get( 'mygadget-example' );
object = mw.storage.getObject( 'mygadget-example' )

Package Gadgets[edit]

Gadgets could always have multiple files, but these were simply merged and executed as one script. MediaWiki 1.33 introduced the "Package files" feature, which allows for a more modular JavaScript design, with the require() function and module.exports pattern to refer to additional files. Additionally, this allows you to include data from JSON files. This feature was limited to modules in MediaWiki core and extensions.

Since MediaWiki 1.38 this feature is also supported in ResourceLoaderWikiModule, and the Gadgets extension was updated to make use of this through a new definition option called "package".

Administrators (eg. Interface administrator on WMF wikis) should take care when writing or reviewing JavaScript code that creates HTML based on text from JSON pages, to escape these to avoid security problems.

For example:

* mygadget[ResourceLoader|package]|mygadget-main.js|mygadget-Foo.js|mygadget-data.json|mygadget.css

Where MediaWiki:Gadget-mygadget-Foo.js exports:

function Foo( config ) {
    // ...

Foo.prototype.format = function () {
    // ...

module.exports = Foo;

and MediaWiki:Gadget-mygadget-data.json:

    "setting": [
    "flag": true

From MediaWiki:Gadget-mygadget-main.js you can then use:

var Foo = require( './mygadget-Foo.js' ); // class Foo
var flag = require( './mygadget-data.json' ).flag; // true

Gadgets may also use module.exports in the main file to define a public interface that can be accessed by other gadgets with require( 'ext.gadget.mygadget' ), just like any other ResourceLoader module.

jQuery Migrate 3[edit]

JQuery was upgraded to version 3 in MediaWiki 1.29 (released in 2017). In jQuery 3.0, several deprecated features were removed by upstream. We temporarily added these back through the jQuery Migrate layer to allow for a gradual transition (T280944).

In the developer console, you may find warnings like the following:

JQMIGRATE: jQuery.fn.size() is deprecated and removed; use the .length property.

JQMIGRATE: Attribute selector with '#' must be quoted

You may also find warnings that only say that something "is deprecated" without "and removed", such as:

JQMIGRATE: jQuery.fn.bind() is deprecated

Warnings that only say "deprecated" are for features that will continue to work even after the jQuery 3 migration layer is removed.

To understand how to update your code, use the following manuals:

The following three issues may be difficult to find and have some extra tips:

  • HTML tags must be properly nested: This means you have used an invalid shortcut like <div/><p/>. In older jQuery versions, this invalid HTML was automatically corrected to <div>, followed by <p>. In jQuery 3 the browser standard behaviour is followed, which means this becomes a <p> inside a <div> like <div><p>..</p></div>. To preserve the old behaviour, explicitly open and close your HTML. Like <div> </div> <p> </p>.
  • Cross-domain AJAX request with JSON-P: If you may cross-domain requests with $.ajax() or $.get() to APIs that returns executable JSON-P scripts (instead of plain JSON), then you must add the { dataType: "script" } option. In previous versions, jQuery would guess between secure JSON and insecure JSON-P scripts.
  • Calling .load() as event method: It is no longer possible to call $img.load(function). Use $img.on("load", function) instead.


As site administrator running MediaWiki 1.35.3 or later, you can choose to turn off migrate layer today already by setting $wgIncludejQueryMigrate to false. Turning off the migration layer improves page load performance, and helps you to verify whether your extensions and gadgets are ready for the upgrade. For example, if you have old code still using methods that were removed in jQuery 3, this may fail as follows.

Uncaught TypeError: $elem.size is not a function.

In MediaWiki 1.37, the migration layer will be off by default. A site administrator may temporarily turn it back on until problems like the above are resolved.

In MediaWiki 1.38, the migration layer will be permanently removed.

This version is not supported.

user.tokens module[edit]

The user.tokens module has been merged into the user.options module bundle. The old module name is now an alias and has been deprecated in MediaWiki 1.35. It will be removed in MediaWiki 1.36 sometime later in 2020. – T235457

To remain compatible, update dependency lists or loader statements from "user.tokens" to "user.options".


The mediawiki.notify module has been merged into the MediaWiki base environment. This module was responsible for providing the mw.notify() function, which in turn lazy-loads the larger mediawiki.notification module. – T233676

To remain compatible, simply remove "mediawiki.notify" from any dependency lists or loader statements.

Module deprecations[edit]


jQuery UI has been deprecated for years, but remains available due to slow switching to alternatives. As a part of on-going efforts to reduce bandwidth cost, the 27 deprecated jQuery UI modules have been collapsed into a single, still-deprecated mega-module (Gerrit, T219604).

To remain compatible, update dependency lists and loader statements from "jquery.ui.*" to "jquery.ui".


The jquery.accessKeyLabel plugin has been available through mediawiki.util since 2014 (MediaWiki 1.24).

Depending on it directly is no longer supported as of MediaWiki 1.34 Update dependency lists and loader statements from "jquery.accessKeyLabel" to "mediawiki.util" to remain compatible.


The mediawiki.RegExp module has been available through mediawiki.util since 2015 (MediaWiki 1.25). – T218339

Depending on it directly is no longer supported as of MediaWiki 1.34. Update dependency lists and loader statements from "mediawiki.RegExp" to "mediawiki.util" to remain compatible.

The mw.RegExp.escape() function has also been deprecated (although kept as alias, shipping with "mediawiki.util"). Replace usage with mw.util.escapeRegExp().


The jquery.tabIndex module existed to help compute a low or high tab index on focusable elements on a page. In most cases this code was redundant. Lines of code involving firstTabIndex() or lastTabIndex() are often best removed entirely. The module is deprecated in MediaWiki 1.34.

// Simply remove
$thing.attr( 'tabindex', $( document ).lastTabIndex() + 1 );

If the effect of this code is still wanted, it can be achieved in a simpler way without this JavaScript plugin. For example, to set a low tabindex, use tabindex="0".

// Remove
$thing.attr( 'tabindex', $( document ).firstTabIndex() );
// Add
$thing.attr( 'tabindex', '0' );

Or, to set a high tabindex, use tabindex="999" instead, like so:

// Remove
$thing.attr( 'tabindex', $( document ).lastTabIndex() + 1 );
// Add
$thing.attr( 'tabindex', '999' );

If you do need the exact behaviour of the original lastTabIndex function, use the following:

// Remove
$thing.attr( 'tabindex', $( document ).lastTabIndex() + 1 );
// Add
var lastIndex = Math.max.apply(null, $.map($('[tabindex]'), function (el) { return +el.tabIndex; }));
$thing.attr( 'tabindex', lastIndex + 1 );

mw.user.tokens editToken[edit]

The editToken key of mw.user.tokens was deprecated in 2016 (MediaWiki 1.26). It has been removed in 2019 (MediaWiki 1.34). – T233442

The csrfToken key should be used instead. For example, change mw.user.tokens.get('editToken') to mw.user.tokens.get('csrfToken').

Note: The mw.Api class has not changed. Code like mw.Api.getToken('edit') will continue to work and should not be changed.

Api modules[edit]

All submodules mediawiki.api.* have been merged into the main module mediawiki.api, so you only have to require the main module, and requiring submodules emits deprecation warnings. These submodules were kept as deprecated aliases to "mediawiki.api", and removed in MediaWiki 1.33.


Method mw.util.wikiGetlink(), which was deprecated since MediaWiki 1.23, has been removed. Use mw.util.getUrl() instead.


The wgEnableAPI and wgEnableWriteAPI keys of mw.config are deprecated as of MediaWiki 1.32, and will be removed in MediaWiki 1.35 (change).

The value of these configuration keys is always true. Any check for them in JavaScript code is redundant and can be safely removed.

Internet Explorer 10 browser[edit]

With this version, we have stopped JavaScript support for IE10. See Compatibility for details.


Deprecated in MediaWiki 1.29 (change), removed in MediaWiki 1.31.

The shim for the native placeholder attribute became obsolete as all supported browsers for JavaScript support this natively. Simply remove the call to .placeholder().


The functionality was originally provided by a module called jquery.mwPrototypes in MediaWiki 1.17 (r76320). This was renamed to jquery.mwExtension in MediaWiki 1.19 (r94227).

The module was deprecated in MediaWiki 1.26, and removed in MediaWiki 1.30.

  • $.trimLeft, $.trimRight: These have native JavaScript methods available now.
  • $.ucFirst: No replacement, rarely used. Simple enough to do in plain JavaScript as str[0].toUpperCase + str.slice(1).
  • $.escapeRE: Moved to mediawiki.RegExp; later moved to mediawiki.util.
  • $.isDomElement: No replacement, rarely used. Use duck-type checks like !!obj.nodeType instead.
  • $.compareArray, $.compareObject, $.isEmpty: No replacement, rarely used.

Legacy removals[edit]

JavaScript functions and variables part of wikibits.js that had been deprecated since MediaWiki 1.17 or 1.18 have been removed:

User-Agent variables: is_gecko, is_chrome_mac, is_chrome, webkit_version, is_safari_win, is_safari, webkit_match, is_ff2, ff2_bugs, is_ff2_win, is_ff2_x11, opera95_bugs, opera7_bugs, opera6_bugs, is_opera_95, is_opera_preseven, is_opera, ie6_bugs, clientPC.

DOM manipulation: changeText, killEvt, addHandler, hookEvent, addClickHandler, removeHandler, getElementsByClassName, getInnerText.

Utilities: setupCheckboxShiftClick, addCheckboxClickHandlers, mwEditButtons, mwCustomEditButtons, injectSpinner, removeSpinner, escapeQuotes, escapeQuotesHTML, jsMsg, addPortletLink, appendCSS, tooltipAccessKeyPrefix, tooltipAccessKeyRegexp, updateTooltipAccessKeys.

How to migrate[edit]

Below is a table containing migration information for the wikibits functionality. Many of the replacements are part of the mediawiki.util module, which is not loaded by default. Please declare your dependency on this module if you refer to mw.util, as described in the development guide.

Gadget type[edit]

See also T42284.


Since early 2011, gadgets with styles (both "only styles" and "styles and scripts") had their styles loaded twice. T42284 and change 308096 fix this bug.

What's new[edit]

This bug was addressed by adding support in the Gadgets extension for the ResourceLoader "type" feature. This allows gadget developers to configure how the module should be loaded

  • type=styles: Load module styles via <link rel="stylesheet">, and completely omits loading any JavaScript files. (Loads styles early, applies styles before skin and page are ready, also works when JavaScript is disabled.)
  • type=general: Load module scripts and/or styles via mw.loader.load(). (Applies styles after the skin and page are ready, right before JS execution, has better caching.)

Gadgets with only styles, internally get type=styles by default. Gadgets with only scripts default to type=general.

Before MediaWiki 1.30, Gadgets with both scripts and styles defaulted to loading both ways, thus loading the styles portion twice. Before that, we sent a warning in the browser console in a transition period that asked developers to set the desired type. After the transition period, we made type=general the default for gadgets that have both scripts and styles.

To load styles through the type=styles system, while also loading JavaScript files, two separate gadget definitions need to be specified.

How to migrate[edit]

Gadget "mygadget" styles loaded twice. Migrate to type=general. See https://phabricator.wikimedia.org/T42284.

If you see this warning, that means your gadget contains both scripts and styles. Here are two ways to fix the warning:

  1. If the styles in your gadget are there to provide styling for things created by the gadget, add "type=general" to your gadget definition ("MediaWiki:Gadgets-definition").
  2. Or – If the styles in your gadget are there to provide styling for things that are part of the skin or on the page, then these styles should not be together with the scripts in the same gadget. Convert the gadget to two separate gadgets. One gadget that is styles-only, and the other with the scripts. If the scripts gadget also has its own styles, then also set "type=general" on the original gadget (per point 1). If you want to keep presenting the modules as one gadget on the Preferences page, use #Gadget peers.

As you can see, in most cases the solution is "type=general." And in the future, this will become the default and we will not load styles twice. Right now, loading twice remains the default for compatibility with older gadgets covered by point 2 above. Changing these mixed gadgets to type=general now would cause some styles to load too late and cause a "flash of unstyled content".

Gadget peers[edit]

See also T42284.

For a long time, gadget authors have been interested in being able to provide a visual enhancement for all pages and also accompanying some scripting logic to apply related changes to interactive interfaces created by other modules. This requires the gadget to have both scripts and styles, but most of the styles are not required by the scripts – rather, the styles should apply directly to the page without waiting for JavaScript. So far this required either creating two gadgets (and requiring users to enable both), or creating a single gadget with the downside of the styles applying slightly after the page loads.

To accommodate the use case of a single gadget providing both page styles (which don't depend on JavaScript) and JavaScript code with its own styles, a new setting was introduced: peers. This is similar to dependencies, except that where dependencies load before the main module (not before the page itself), peers will allow one to reference a separate gadget module that will be loaded regardless of whether JavaScript is enabled.

For example:

* example [ResourceLoader|dependencies=mediawiki.util|peers=example-pagestyles] | example.js | example.css
* example-pagestyles [hidden] | example-pagestyles.css

This will register a gadget named "Example" in the preferences which, if enabled, will load example-pagestyles before the page renders. And, once JavaScript is available, the example module will also be loaded with its own dependencies, styles and scripts.

Internet Explorer 9 and pre-ES5 browsers[edit]

With this version, we have stopped JavaScript support for IE9 and other browsers that do not support ES5. See Compatibility for details.

This version is not supported.

Legacy default: mediawiki.util[edit]

The $wgPreloadJavaScriptMwUtil option was removed. This option allowed third-party MediaWiki administrators to re-enable the unconditional preload of mediawiki.util by default for all users (for backwards compatibility). It was disabled by default since MediaWiki 1.26, and has been disabled on Wikimedia wikis since 2014. Extensions, skins, gadgets and scripts that use the mediawiki.util module must express a dependency on it.


The internal Wikimedia domain "bits.wikimedia.org" was deprecated sometime mid-2015. The following common paths should be migrated to avoid breakage once the domain is decommissioned (T107430).

  • bits.wikimedia.org/:domain/load.phphttps://:domain/w/load.php . Moved back to local domains, alongside /w/index.php and others.
  • bits.wikimedia.org/static-current/*https://:domain/static/current/: Moved to local domain, sharing a hostname-agonistic Varnish cache.
    • bits.wikimedia.org/skins/*https://:domain/static/current/skins
  • bits.wikimedia.org/static-1.xx-wmf.X/*https://:domain/w/*: Specific versions can now be accessed through the regular script path. Wikimedia's multiversion entry point automatically serves the file from to the wikis' current MediaWiki version. (T99096)
    • bits.wikimedia.org/static-1.xx/skins/* https://:domain/w/skins/*
    • bits.wikimedia.org/static-1.xx/extensions/* https://:domain/w/extensions/*
    • bits.wikimedia.org/static-1.xx/resources/* https://:domain/w/resources/*

Internet Explorer 8[edit]

Following the deactivation of JavaScript in Internet Explorer 6 and 7 in MediaWiki 1.24, JavaScript has been deactivated in Internet Explorer 8. See Compatibility for details.

Legacy gadgets[edit]

Gadgets are now required to use ResourceLoader. For many Gadgets, migrating to ResourceLoader will be as easy as adding [ResourceLoader] to its definition on MediaWiki:Gadgets-definition. If after adding that, the gadget is not working properly, consult the rest of this page to look for functionality that may have been removed since the gadget was last maintained. If you run into any issues or find features that don't work without a clear way of making it work, please reach out to MediaWiki developers and fellow gadget authors on the talk page, via IRC, or on the wikitech-l mailing list.

Global variables are not global[edit]

When ResourceLoader loads a gadget script, it is not executed in global context. This means that local variables you define in the script are actually local, and not assumed to be also global. They are local to the function your code is wrapped in. It's best to modularize your code to avoid using globals, see "Globals" in MediaWiki's JavaScript coding conventions. However, if you need to export a variable to the global scope, you can explicitly assign them as window properties. For example:

// This is a local variable
var foo;
// This is a local function
function bar() {

// This is a global variable (accessible from other scripts, and from legacy event handlers, e.g. onclick="javascript:Quux();"
window.Quux = function( width, height ) {

Code within your gadget can access foo and bar. Code outside the gadget (or code evaluated as separate programs, such as legacy onclick handlers), can only access Quux..

As of August 2015, ResourceLoader debug mode still executes scripts in global scope (phab:T64605), so your code may seem to work fine in debug mode but be broken in regular mode.

Font mw-geshi[edit]

The font-size of ‎<syntaxhighlight> was often too small by default due to a font-family CSS bug. This was fixed in MediaWiki 1.26 (see (phab:T28204).

The mw-geshi, source-css, source-javascript and related classes no longer exist. Related code such as the following can be safely removed:

/* Fix <syntaxhighlight> text size. [[phab:T28204]] */
div.mw-geshi div,
div.mw-geshi div pre,
pre.source-lua {
    font-family: monospace, Courier !important;

Inline scripts[edit]

To inject JavaScript inline, use ResourceLoader::makeInlineScript() to wrap the JavaScript code in an anonymous function that can access MediaWiki-related objects properly, and OutputPage::addScript() to add the results to the page source for execution.

For example:

$outputPage = RequestContext::getMain()->getOutput();

$js = 'alert("hello world");';
$wrappedJS = ResourceLoader::makeInlineScript($js);

Legacy removals[edit]

The jquery.delayedBind JavaScript module, deprecated in MediaWiki 1.23, has been removed. See phab:rMW8f2ebcbf6769.

Internet Explorer[edit]

Browser support for Internet Explorer 6 and 7 changed from Grade A to Grade C. This means JavaScript is no longer executed in these browser versions. See Compatibility for details.


This method has been deprecated in favour of mw.notify.

The jsMessage message was designed to be a drop-in replacement fully compatible with the legacy wikibits jsMsg function (deprecated since 1.17, removed in 1.29). The 2012 notification system on the other hand was designed with developer usability and security in mind.

For most cases, the new method is just as easy to use as the old one, and requires only a the same single parameter that represents the message. For example, with plain text:

// Deprecated (dependencies: mediawiki.util)
var msgText = 'Hello world';

// New, as of 2012 (dependencies: mediawiki.notify)
var msgText = 'Hello world';

And another example, with a DOM element, or a jQuery object:

// Deprecated (dependencies: mediawiki.util)
var $myWidget = ExampleWidget.create( {
    having: '2-buttons',
    toggle: '#sidebar'

// New, as of 2012 (dependencies: mediawiki.notify)
var $myWidget = ExampleWidget.create( {
    having: '2-buttons',
    toggle: '#sidebar'

If you're currently using raw HTML with mw.util.jsMessage(), the simplest way to migrate is to do what jsMessage used to do internally for you, which is to parse the HTML and place the node(s) in a jQuery object, as follows:

// Deprecated (dependencies: mediawiki.util)
var msgHtml = '<form><button>Click me</button></form>';

// New, as of 2012 (dependencies: mediawiki.notify)
var msgHtml = '<form><button>Click me</button></form>';
var $msg = $($.parseHTML(msgHtml));

New diff styles[edit]

This version introduces a new diff view, greatly improved in clarity especially for whitespace and other small changes and colour-blind users. If your wiki has custom CSS for the diffs, they may be in conflict with the new style (as happened on ptwiki and srwiki). You are recommended to remove the old code (or if still wanted by some users, update it to work with the new layout and create a gadget for it so that users can opt-in to it still).

wikitable style updates[edit]

As of MediaWiki 1.19 a few bugs have been fixed with the wikitable class (see phab:T32485 and phab:T35434 for more info). If your wiki maintains a legacy synonym of this class (e.g. "prettytable") you need to update its CSS to match the current style in core.

The current style as of 1.19 can be found here. Copy those rules to your wiki and replace "wikitable" with the synonym (example for nl.wikipedia).

If your wiki doesn't keep something like this, then no update is necessary and everything should take care of itself.

File page checkered background[edit]

The checkered background often applied to transparent file namespace pages is now part of the software. Local rules like the following should be removed (because they are redundant, and actually cause an additional unnecessary HTTP request for the image)

/* Put a checker background at the image description page.
   Only visible if the image has transparent background.
#file img {
	background: url("//upload.wikimedia.org/wikipedia/commons/5/5d/Checker-16x16.png") repeat;


Trackbacks were removed from MediaWiki core, so any styling targeting #mw_trackbacks can be removed.

Protocol-relative urls[edit]

This change only applies to Wikimedia Foundation wikis.

As of MediaWiki 1.18 there is native support for protocol-relative wiki installations. This means that a wiki could be accessible from both http://example.org/ and https://example.org./ To make it possible to a share a common cache for as much as possible, we make use of a technique called protocol-relative urls. Although browsers have supports this for ages, script writers generally aren't very familiar with it until fairly recently. Briefly explained, this means that <img src="//meta.wikimedia.org" /> when on "https://example.org" will be automatically expanded by the browser to https://meta.wikimedia.org./ This is much like (for example) <img src="foobar.jpg" /> or <img src="/w/foobar.jpg" />, which are are automatically expanded to "http://mediawiki.org/w/foobar.jpg".

Depending on how the scripts were written this may require some changes to be made to your scripts. If you use the following method to detect whether the script is executed on a certain wiki, this change will break your script:

if ( wgServer === 'http://en.wikipedia.org' ) {
	// Doesn't work anymore!

because wgServer is now "//en.wikipedia.org". For a few years there has been another config variable, called "wgDBname". You should use that instead to differentiate wikis, like:

if ( mw.config.get( 'wgDBname' ) === 'enwiki' ) {
	// English Wikipedia!

Alternatively, you can use wgServerName which is without the protocol or port:

if ( mw.config.get( 'wgServerName' ) === 'en.wikipedia.org' ) {
	// English Wikipedia!

"Enabled by default" (Gadgets extension)[edit]

As of the version of the Gadgets extension at the MW 1.18 branchpoint, there is a new feature that allows a gadget to be opt-out instead of opt-in based. By setting "[default]" (or adding "|default" to an existing section) the gadget will be enabled by default for everybody, unless a user has specifically opted out by unticking the checkbox on Special:Preferences#mw-prefsection-gadgets.

Note that this also loads it for all anonymous users. Gadgets that are only for logged-in users should be additionally restricted by, for example, requiring certain user rights.

See also Extension:Gadgets#Options.


The actual paths have not changed, but getting the path to the API and index.php has become a lot easier. This also makes the code more portable as it has no hardcoded wiki-specific paths.

This is how it used to go in many gadgets.

var foo = 'bar';
var apiUrl = '//www.mediawiki.org/w/api.php?foo=' + encodeURIComponent( foo ) + '&baz=quux';

$.ajax( { url: apiUrl, ... } );

Instead use something like one of the following:

// Behold, mw.util.wikiScript!
var foo = 'bar';
var apiUrl = mw.util.wikiScript( 'api' ) + '?foo=' + encodeURIComponent( foo ) + '&baz=quux';

$.ajax( {
	url: apiUrl,
} );

You may also want to use $.param to automatically escape and create things properly in the query string:

// $.param is also awesome. No need for encodeURIComponent that way :)
var foo = 'bar';
var apiUrl = mw.util.wikiScript( 'api' ) + '?' + $.param( {
	foo: foo,
	baz: 'quux'
} );

$.ajax( {
	url: apiUrl,
} );

You can even use the data option of $.ajax, that abstracts away the need to deal with the query string entirely:

// No longer needed to inject the '?' or '&' in the url
$.ajax( {
	url: mw.util.wikiScript( 'api' ),
	data: {
		foo: 'bar',
		baz: 'quux'
	}, ...
} );


See also jQuery

As of 1.17 the jQuery library is loaded by default on all MediaWiki pages. Each MediaWiki release will keep it up to date with the latest version of jQuery. If you used to load jQuery from within your script, (e.g. from ajax.googleapis.com), make sure you remove that. If you load jQuery more than once on a page, it overwrites the earlier version. Other scripts break because they may not work with an older version of jQuery.

Also, by overwriting the jQuery object, any plugins that were bound to that object are also lost.

Global identifier "$j" has been deprecated. Use jQuery or $ instead.

Tabs (vector)[edit]

In 1.17 the HTML construction for the navigation tabs has changed from <li><a><span /></a></li> to <li><span><a /></span></li>. The most common situation in which this causes problems is where scripts assume the presence of the span element when, for example, customizing the tab for "Main Page". Before 1.17 this usually meant that wikis had a different implementation for Monobook and one for Vector (or only one for each and the other was distorted).

Please use MediaWiki:Mainpage-nstab or refer to Snippets/Main Page tab for a script that will work in both Vector and Monobook for 1.17.

Adding portlet links[edit]

The legacy function addPortletLink has been rewritten as mw.util.addPortletLink. The syntax and argument order is fully backwards compatible. The differences

  • Support for all core skins now
  • Support for simple id-selector as 'nextNode' (see documentation for details).

Some wikis may have re-defined / overwritten the addPortlinkLink function to support a few extra skins. This is no longer needed. The function definition should be removed and calls adjusted to mw.util.addPortletLink.

The legacy version of addPortlinkLink has been preserved as-is in case some edge cases would behave differently (for that reason the addPortlinkLink does not redirect to mw.util.addPortlinkLink)


The legacy array mwCustomEditButtons has been refactored into the mw.toolbar library. The global array still exists in wikibits to avoid fatal errors but is no longer used due to race conditions. Code may run too late when the toolbar already exists. Using mw.toolbar.addButton will work always, even if the toolbar has already been created.

See mw.toolbar Documentation.

Note that mw.toolbar, just like the old mwCustomEditButtons array, are associated with the classic toolbar. The current default wikitext editor is WikiEditor, which has its own API. See Extension:WikiEditor/Toolbar customization for more information.


The legacy functions such as sajax_init_object have been deprecated. Instead, mw.Api from the mediawiki.api module, or jQuery.ajax.

Migration guide:

Client testing[edit]

Checking which browser, platform, layout engine etc. has should now be done with jQuery.client.

  • is_safari, is_chrome etc. are deprecated
  • No need to navigator.userAgent.indexOf("MSIE 6")==-1 etc.

Sysop script[edit]

New in MediaWiki 1.17 is a user groups module that can automatically load scripts and styles from the MediaWiki namespace for a particular user group. For example, if the wiki has MediaWiki:Group-sysop.js, this script is automatically loaded for all users in that group.

This should obsolete customisations wikis may have with regards to loading MediaWiki:Sysop.js with importScript inside Common.js.


If you need certain scripts like jQuery UI's dialog or datepicker, instead of doing something like:

importStylesheetURI( mw.config.get( 'wgExtensionAssetsPath' ) + '/Example/css/jquery-ui-1.7.2.css' );

$.getScript( mw.config.get( 'wgExtensionAssetsPath' ) + '/Example/js/jui.combined.min.js', function () {
} );

Instead use this:

mw.loader.using( ['jquery.ui.dialog', 'jquery.ui.datepicker'], MyTool.init );

Or if you need to delay initialization until document.ready:

mw.loader.using( ['jquery.ui.dialog', 'jquery.ui.datepicker'], function () {
	$( document ).ready( MyTool.init );
} );

When a script depends on another module, such as oojs or mediawiki.util, you will need to declare this as a "dependency". This is because modules are loaded on-demand and asynchronously (in consecutive order: all at the same time), so a script needs to make sure a module has been loaded before it can use its methods. On-site modules, like gadgets, have a registry to declare these dependencies. For user scripts, one has to wrap code with mw.loader.using() .

While this has been required since 2011, many scripts have continued to work without declaring their dependencies. Scripts may have worked before by accident as long as at least one user script (that used the same methods) did declare their dependencies and happened to load earlier.

With MediaWiki 1.19, page view performance has been optimised to use fewer modules by default. This makes it increasingly more important to declare the dependencies. Otherwise, your script may fail because any of the 1000+ modules you might refer to in your code would not be loaded yet. Loading everything all the time would be much too slow.

The only two base modules that are always present are mediawiki and jquery.

In practice[edit]

Use mw.loader.using() to declare any modules that you need before executing the contents of "function". You can pass multiple modules as an array of strings.

mw.loader.using( ['mediawiki.util', 'oojs', 'jquery.cookie'], function () {

	/* some other script that uses $.cookie */

	/* some other script that uses mw.util and OO.EventEmitter() */

} );

Global wg variables[edit]

As of MediaWiki 1.17, the global config variables are deprecated. Rationale to clear the global namespace, working towards a reality where most of the core libraries will be object oriented as part of the mw object. Configuration is managed through an instance of mw.Map in mw.config. It is also supporting the behaviour of more script executing in their own local/private scope as opposed to the global scope.

Legacy globals will be kept for backwards compatibility, but people should start migrating so that they may removed in a future version of MediaWiki (task T35837).

// One variable
if ( mw.config.get( 'wgCanonicalSpecialPageName' ) === 'Search' ) {
	// Example for Special:Search

if ( mw.config.get( 'wgGlobalGroups', [] ).indexOf( 'global-rollbacker' ) !== -1 ) {
	// Example for users in the global group "global-rollbacker".

// Multiple variables
var conf = mw.config.get( [
] );
if ( conf.wgAction === 'edit' ) {
	console.log( 'Example when editing a page', config.wgScript );

More info: ResourceLoader/Default modules#mw.config

Ready, onload, hook[edit]

Check JavaScript deprecation overview for "addOnloadHook". Use $( function ); instead, or $( fn ); for short.

New CSS declarations in core[edit]

Headings overflow hidden[edit]

overflow:hidden for any of h1, h2, h3, h4, h5 and/or h6 can be safely removed from stylesheets as this is now part of the core.

Italic redirects[edit]

Links to redirects now appear italicized by default on Special:AllPages, Special:PrefixIndex, Special:Watchlist/edit and in category listings. Overrides like the following are redundant and can be safely removed.

.watchlistredir {
 font-style: italic;


Per phab:T22276, input#wpSummary's width is now set in Vector as well (instead of just Monobook).

UsabilityInitiative no more[edit]

As of 1.17 the functionality developed by the UsabilityInitiative has been extracted to stand-alone extensions. Buttons like "#pt-optin-try" no longer exist. You can enable/disable these functions like other extensions via Special:Preferences.

Scripts and styles doing things like "HideUsabilityOptIn":

#pt-optin-try {
	display: none !important;

should therefore be deleted entirely as the button no longer exists.

Preformatted JS/CSS pages[edit]

It's no longer useful to wrap these pages in /* <pre> */ or // <syntaxhighlight lang="javascript"> etc. In newer versions of MediaWiki, these pages are rendered as code automatically (including syntax highlighting when available). See also task T6801.

Table sorter[edit]

The old table sorter in wikibits.js was removed in favour of jquery.tablesorter.

Variables such as ts_alternate_row_colors, and functions like ts_parseFloat and ts_dateToSortKey no longer exist.


As of 2008, the importScript function commonly defined by communities locally became a built-in part of MediaWiki ("wikibits.js"). Wikis that previously defined this function themselves, are able to remove that. The new built-in function is automatically used. The same also applies to importStylesheet, importStylesheetURI and importScriptURI.

Note that importStylesheetURI and importScriptURI were subsequently deprecated in 2011 with MediaWiki 1.17, and disabled on mobile sites like https://en.m.wikipedia.org/. Use mw.loader.load instead.


As of 2008, the function addPortletLink is part of MediaWiki. Many wikis and gadgets have created functions like addLink, addLiLink, addlilink etc. these should be removed as they most likely don't support different skins (ie. only Monobook, not Vector or older skins). Be sure to check the syntax as there is no way of knowing the creator of those local functions used the same parameter order.

Note: The global function was deprecated in 2012 and moved to the mediawiki.util module as mw.util.addPortletLink()


As of 2008, the function appendCSS is part of MediaWiki. Wikis that have defined this function themselves may remove that. It will automatically use the new function.

Note: The global function was deprecated in 2012 and moved to the mediawiki.util module as mw.util.addCSS()

HTML bugs in core[edit]

html lang[edit]

This bugfix is obsolete as MediaWiki does this correctly by default. (example)

var htmlE = document.documentElement;
htmlE.setAttribute('lang', mw.config.get('wgUserLanguage'));

CSS declarations new in core[edit]


The .wikitable CSS class is part of MediaWiki. Wikis that previously defined this class in their Common.css should remove it. Do check if the wiki has any customisations that should be retained (e.g. different background-color, or font-size).


The .plainlinks CSS class is part of MediaWiki. Wikis that previously defined this class in their Common.css should remove it.

Alternative names for this feature, that were in popular use on Wikimedia Foundation wikis, include: .plainlinksneverexpand and .nounderlines. Replace any usage on wiki pages "plainlinks", and afterward these alternate styles may also be removed. For example, use search and query for insource:plainlinksneverexpand.


The CSS classes .mw-plusminus-pos, .mw-plusminus-null, and .mw-plusminus-neg are now implemented by MediaWiki.

External URLs[edit]

Icons for protocols like HTTP, IRC, etc. and file types like PDF are now supported by MediaWiki.

Tooltip and accesskeys[edit]

Scripts like ta['pt-userpage'] = new Array('.','My user page'); are ignored. It was deprecated in 2009. The function akeytt() no longer exists. Tooltips and accesskeys are now supported from core. The most common values that wikis used with ta[] are the same that have now been integrated into the core (ie. "." for "my user page"). They can still be modified, if really needed, by sysops in MediaWiki-messages (no need for JavaScript workarounds anymore).

As of MediaWiki 1.19 the global dummy placeholder ta = new Object(); was removed from wikibits.js. Code trying to add members to it will likely emit an exception.

Best practices[edit]

The below are additional advices not related to a particular MediaWiki release, but rather general best practices.

Avoid document.write()[edit]

Do not use this method, as it can cause a page to become visually blanked. Instead, use jQuery to modify the document (adding elements, changing things etc.). To load external resources, use the import/loader functions instead.

Example: replace

document.write('<script type="text/javascript" src="'
             + 'https://commons.wikimedia.org/w/index.php?title=MediaWiki:Gadget-HotCat.js'
             + '&action=raw&ctype=text/javascript"></script>');



Event binding[edit]

Binding input events to callback functions can be hard to do in cross-browser compatible way for all browsers that MediaWiki supports.

It is recommended that you use jQuery for event binding. See the JavaScript deprecation overview on "addHandler" for examples.

Encoding and escaping[edit]

When working with regular expressions, user input and/or urls must always be encoded or escaped.


Do not extend native JavaScript constructors with non-standard methods (e.g. String.prototype.foobar, Regex.myMethod, Array.prototype.inArray etc.).

Such non-standard methods should be defined in your own namespace instead, for example MyThing.foobar, or using module.exports/require.


Before 2015, it was common for user scripts and gadgets to define fallback method for standard features of newer JavaScript engines. This is no longer needed in most cases, because the Base environment already ensures ES5 or later. This means ES5 methods such as String#trim and Array#forEach can be used directly.

Before MediaWiki 1.32, the es5-shim module was bundled with MediaWiki to automatically define polyfills if needed. It could be used like so:

// This using() command will immediately execute as "then()" in modern browsers.
// In older browsers, it loads es5-shim.js first, and then executes your "then()".
mw.loader.using( 'es5-shim').then( function () {
	console.log( '    bar    '.trim() ); // "bar"
	[ 'a', 'b' ].forEach( function ( val ) {
		/* .. */
	} );
} );

Getting URL parameter values[edit]

Functions like getURLParamValue, getParamVal, getParamValue, etc. are very common across wikis. Some are better than others (i.e. what if a parameter appears twice? (it should return the last one), does it ignore anything after the #tag?). As of 1.17 mw.util.getParamValue is available everywhere and takes these factors into account. Perform a full-text all-namespace search for these function names. If they are widely used perhaps make a note about it in the local village pump. Any site-wide scripts should be updated to use the mw.util function. If there are any serious problems with the local implementation (like not escaping the value for regex), it may be wise to redirect the function:

function getURLParamValue( p, url ) {
	return mw.util.getParamValue( p, url );

Avoid use of !important[edit]

CSS stands for Cascading Style Sheets. Cascading means what comes later overwrites what came earlier. In most cases there is no need to use !important. See the following example:

.my-element { color: blue; }
.my-element { color: green; }

Text inside <strong class="my-element"> will now be green.

Keep gadgets central[edit]

Use Meta.wikimedia.org or MediaWiki.org to store Gadgets' code, then import it into various local mediawiki.

Interface administrators: To update a gadget on your wiki:

  • Check MediaWiki:Gadgets-definition on your wiki and find the gadget in question.
  • The part after the pipe (|) is the scriptname (eg. "UTCLiveClock.js").
  • Go to MediaWiki:Gadget-<scriptname> (eg. MediaWiki:Gadget-UTCLiveClock.js)
  • Remove everything and replace with the code in they grey area below the scriptname in the list. For an example on how this is done, check out LiveClock on Simple Wikipedia.

Below is a list of gadgets that are :

  • centrally stored
  • compatible with 1.17
  • work in Monobook and Vector
  • can be loaded into any mediawiki, from WMF or external.


  • UTCLiveClock
  • contribsrange
  • modrollback
  • QPreview
  • ShortDiff
  • lastdiff Check Snippets/Last revision action
  • HotCat
 * This imports the latest version of HotCat from Commons.
 * HotCat is a gadget to make changes to categories much easier.
 * Full documentation can be found at https://commons.wikimedia.org/wiki/Help:Gadget-HotCat
  • WikiMiniAtlas
 * WikiMiniAtlas is a popup click and drag world map.
 * See [[meta:WikiMiniAtlas]] for more information.
 * Maintainers: [[w:User:Dschwen]]
  • Navigation Popups (MediaWiki:Gadget-popups.js and MediaWiki:Gadget-popups.css respectively)
@import url('https://en.wikipedia.org/w/index.php?title=MediaWiki:Gadget-navpop.css&action=raw&ctype=text/css');

jQuery optimization[edit]

Use API instead of index.php[edit]

XML retrieved by invoking GET and POST methods on index.php is incompatible with HTML 5, which is the default as of 1.16 (and WMF sites since 17th of September, 2012). You should update code to use api.php, JSON format and jQuery.ajax immediately. Use the ResourceLoader modules that do this for you to simplify interactng with the API, including mediawiki.api.

A temporary fix for problems with DOM parsing of XML retrieved via AJAX: For example the method getElementById("foobar") on a XML object from Mozilla's DOMParser stopped to work as before. Replacing the getElementById with $('#foobar', client.responseText).get(0) might work without many other changes to your code. Updating your script to the above mentioned methods is strongly recommended, however.


See also[edit]