Catwatch is a new MediaWiki feature that tracks category membership changes. It is possible to view these changes in the recent changes and watchlists.
Enabling the feature on a wiki
The feature is currently controlled using the
$wgRCWatchCategoryMembership global which is by default set to false.
To enable the feature set this to true.
Even when enabled on a wiki the default settings hide the category membership changes from users.
Showing the changes
To show the changes on recent changes click "Show page categorization". To see them on a watchlist disable the checkbox for hiding "page categorization".
Showing the feature by default (per user)
There are 2 user preferences that currently hide the feature by default.
To show the changes by default go to your user preferences and change the setting "Hide categorization changes" for recent changes and for your watchlist.