Welcome to the gadget kitchen. This is a tutorial for how you can write and use gadgets and user-scripts in JavaScript.

What are user scripts and gadgets? edit

MediaWiki allows anyone to write public JavaScript code to immediately change the behavior of the software. This code can be shared with other users. This code is located in wiki pages.

If you're running your own copy of MediaWiki, $wgAllowUserJs needs to be enabled for user scripts to work, and the Gadgets extension needs to be installed to make it possible to promote individual scripts to gadget status. For a nicer development experience, ensure that the CodeEditor extension is installed on your wiki.

Write your first user script edit

In this section, you create an example user script which calculates the estimated reading time of a wiki page.

  1. Ensure you are logged in.
  2. Visit Special:MyPage/common.js. This page holds your personal JavaScript that is loaded on every page view (except for Special:Preferences).
  3. Either create the page or edit the page if it already exists.
  4. Copy the following six lines and paste these lines into the page:
    var numWords = $("#mw-content-text > div").text().split(" ").length;
    var headerWords = $("h1").text().split(" ").length;
    var totalWords = numWords + headerWords;
    var timeInMinutes = totalWords / 200;
    var header = $("h1").text();
    $("h1").text(header + " (it will take you " + timeInMinutes + " minutes to read this page)");
  5. Click "Publish changes".
  6. Go to any page. Look at the title.

This example user script is taken from ChickTech High School Kickoff 2017/Tasks . There are more examples for simple user scripts on that page.

In general, check out the JavaScript coding conventions to write JavaScript that complies with MediaWiki's style.

Developing user scripts and gadgets edit

This section lists resources which are either needed or helpful for non-simple user scripts.

ResourceLoader edit

Gadgets must use ResourceLoader. ResourceLoader is a core feature of MediaWiki that intelligently delivers JavaScript and CSS assets to users and readers. Because Gadgets are coded in JavaScript, as a Gadget coder you're bound to interact with ResourceLoader.

Your gadget should load useful ResourceLoader modules.

OOUI edit

OOUI is a JavaScript library with user interface elements (for example pop-up windows) specifically for use in MediaWiki. The library Using OOUI in MediaWiki#Gadgets can be used in gadgets.

MediaWiki Action API edit

See API for more information.

If your gadget uses the MediaWiki API, add the "?callback=?" parameter to the API URL if you are trying to make an API request that would violate the same-origin policy (e.g. making a request to the Commons API from Wikipedia). This triggers the use of JSONP and enforces certain restrictions.

VisualEditor edit

See VisualEditor/Gadgets for a tutorial specifically for VisualEditor gadgets.

Debugging user scripts and gadgets edit

Privacy and external content edit

You should not load external resources that may harm users privacy. In Wikimedia wikis, the following domains are considered safe:

  • *.wiktionary.org
  • *.wikimedia.org
  • *.wikibooks.org
  • *.wikisource.org
  • *.wikiversity.org
  • *.wikinews.org
  • *.wikiquote.org
  • *.wikidata.org
  • *.wikivoyage.org
  • www.mediawiki.org
There was a Jenkins job (job code) that automatically checked gadgets for this principle, but this job has not been actively run since 2022.

A more complex user script example edit

Check out MediaWiki:Tutorial-QuickRC.js which uses mw.loader, mw.util, mw.html, mw.user from ResourceLoader, the MediaWiki Action API, a jQuery UI dialog, jQuery AJAX, and jQuery event binding.

Copy and paste the contents of MediaWiki:Tutorial-QuickRC.js into your Special:MyPage/common.js.

The result should be the same as above, but now you can modify the script, play with it, and replace it with something else entirely.

Clicking "Preview" (or using the keyboard shortcut, typically Shift+Alt+P) in the editor will also execute the latest version of the script. This is a good way to iterate without saving the page. Remember, nothing is saved until you press "Publish page".

Load an existing user script edit

In the previous section, you copied the content of a user script. In this section, you will load the existing script MediaWiki:Tutorial-QuickRC.js instead.

  1. Ensure you are logged in.
  2. Visit Special:MyPage/common.js. This page holds your personal JavaScript that is loaded on every page view (except for Special:Preferences).
  3. Either create the page or edit the page if it already exists.
  4. Copy the following text and paste it into the page:
  5. Click "Publish changes". You should now have a link in the "Tools" section called "Quick changelog".
  6. Click "Quick changelog". You get a pop-up window. It shows you a subset of the recent changes on this website.

Use a script on another Wikimedia wiki edit

If you want to use a script on another Wikimedia website (for example English Wikipedia instead of MediaWiki.org), you perform the same steps as above: you tell ResourceLoader to load your code. Visit your common.js on English Wikipedia, and add the following:


You can also load the user script which you just created above, by changing MediaWiki:Tutorial-QuickRC.js in the previous line to User:YourName/YourScript.js (replace YourName and YourScript accordingly). This first requires that you do not store the code of your user script in Special:MyPage/common.js itself but instead in a separate sub page of your user page.

This also helps to keep code in one single place, so you have to update code in only one place.

Disadvantages and problems of gadgets edit

  • Gadgets are developed by community members. As of today, there is no formal code review required for gadgets on Wikimedia sites (see phab:T71445). Please follow the best practices listed on this page.
  • On Wikimedia sites, the process how to "promote" a user script to a gadget in the "Gadgets" tab of the user preferences is not always clear. You will have to find an interface administrator and might have to provide deployment instructions to them.
  • Wikimedia lacks a systematic process for re-using, modifying and contributing to existing user scripts and gadgets.

Ideas what to work on edit

Some Wikimedia community members may share their ideas what they would like to see implemented by someone else.

Deploying or enabling a gadget edit

If your user script should become a gadget (see the definitions above) on a wiki, the following steps are needed:

  • Steps for the user script author:
    • Recruit an experienced developer to review your gadget code. There is no formal process to do so.
    • Check with community members if there aren't any concerns with enabling the gadget on a wiki. For the website MediaWiki.org itself, this would be Project:Village Pump.
    • Recruit a site administrator with interface rights. See the page Special:ListUsers/interface-admin on your wiki.
  • Steps for the interface administrator:
    • Copy your JS & CSS files in the MediaWiki: namespace on your wiki, and make sure the page names have the prefix Gadget-.
      Example: MediaWiki:Gadget-userfeedback.js
    • Define the gadget on the MediaWiki:Gadgets-definition page of your wiki. That includes the modules used, dependencies, JS, and CSS file names, etc. This will allow users to enable the gadget on the Special:Preferences page of your wiki.
      Example: userfeedback[ResourceLoader|default|dependencies=ext.eventLogging]|userfeedback.js|userfeedback.css
    • Create a page for the gadget in the MediaWiki: namespace with prefix Gadget-. This will generate a label for the gadget on the Special:Preferences page of your wiki.
      Example: MediaWiki:Gadget-userfeedback

Contributing to user scripts edit

If a user script is made by another user you may be able to contribute to it. You can do this by making a copy of the user script as a subpage of your own user page. Then replace the original user script you had enabled with the one that is a user page in your common.js. Proceed to make edits as you please to your copy of the script. If you want the script to contain the changes you made to your copy of the script, you should ping the author of the script on the discussion page of the original user script with the page that contains your changes and ask them to add the changes. If the user is no longer active, then you should notify the community that your version of the script exists by linking the script on your wiki's list of scripts.

Related pages edit