In T108630#1567874, @matmarex wrote:

The problem with HotCat is that the code is extremely unmaintainable, written a long time ago using techniques which were good then but have better alternatives now, and tries to be compatible with ancient versions of MediaWiki – which has negative effects on modern versions of MediaWiki, especially because it keeps breaking when implementation details of core scripts or ResourceLoader are changed for this reason.

Please, do not convert HotCat in its current form to an extension. It would not improve its maintenance (I can guarantee that no one will step up to maintain it, because we value our sanity), and it will make it more difficult for gadget writers to maintain it.

@matmarex : Could it be re-written from scratch, and then be more maintainable? For that matter, could the main features of HotCat and/or Cat-a-lot be merged into MediaWiki core? These are key tools for Commons, and HotCat is used on all of the larger wikis.

The user interface resembling HotCat is already in core - mw.widgets.CategoryMultiselectWidget - and supports the different types of search offered by HotCat - mw.widgets.CategoryMultiselectWidget.SearchType.

VisualEditor offers this functionality with the ve.ui.MWCategoryWidget, and there is a task to T147811: Unify mw.widgets.CategorySelector and ve.ui.MWCategoryWidget.

The user interface resembling HotCat is already in core - mw.widgets.CategoryMultiselectWidget

This is the same widget that UploadWizard uses to let you add categories. Seems like this should be pretty straightforward to implement.

Note that if HotCat was extensionized, it would probably need to be an opt-in feature since the main reason most wikis don't make it a default gadget is that they're worried about mis-use by newbies. Of course this could be left up to the consensus of each wiki community.

Just wanted to note that VE already has this functionality in VE → Page options → Categories, but without using mw.widgets.CategoryMultiselectWidget.

These two existing interfaces are missing a bunch of features of HotCat, e.g. navigating over parent categories and subcategories, setting sortkeys, or following category redirects. (They also obviously have no ability to save the changes, it's just a selector for categories.) This is actually a pretty nice description of HotCat's features: https://commons.wikimedia.org/wiki/Help:Gadget-HotCat#User_interface

Rather than add all the advanced features of HotCat, I would suggest retaining the HotCat gadget as a tool for power-users, and disabling the simple Beta Feature version if they have HotCat enabled. This is similar to how Page Previews interacts with Navigation pop-ups.

In T104394#3901925, @Prtksxna wrote on 16 Jan 2018,:

Just wanted to note that VE already has this functionality in VE → Page options → Categories, but without using mw.widgets.CategoryMultiselectWidget.

This VisualEditor functionality is now integrated with the category links footer on pageviews by default (T291691). This was deployed to WMF wikis in Oct 2025, and released as part of MediaWiki 1.45. It works from the same place as where HotCat has its interface, but instead of opening HotCat, it opens the VisualEditor category widget.

VisualEditor is deployed on all WMF wikis, and VisualEditor has been bundled with MediaWiki since 2019 (MW 1.35).

This means the general problem of "category editing is hard" has been solved for content pages (e.g. articles) and most wikitext pages (Help pages, Project pages, Category pages, etc).

A notable caveat is that the VisualEditor category edit link, does have a few intentional conditions:

• The implict condition is that it is only available where VisualEditor is available. While VE is deployed on all WMF wikis, it is not available for all pages on a wiki. Notably we don't enable VE on Talk-pages, User-pages, Template-pages, and Lua modules.
• Wiktionary entries are a notable case where the main namespace of a wiki is not VE-enabled. Ref https://en.wiktionary.org/wiki/banana#catlinks. Ref T52000.
• File description pages on Wikimedia Commons are not VE-enabled. Commons is a heavy consumer of the category system.

39 WMF wikis enable the HotCat gadget by default for all users (Global Search).

It is no surprise then these 39 wikis includes Commons, and 10 Wiktionaries.