This is the {{category handler}} meta-template.

It helps other templates to automate both categorization and category suppression.

Already when used with its default settings this template prevents auto-categorization in some namespaces and on some pages where we usually don't want categorization. Thus even the most basic usage like "{{category handler|[[Category:Somecat]]}}" sees to that templates don't auto-categorize in the wrong places.

This template makes it easy to choose in what namespaces a template should and should not categorize. And it makes it easy to use different categories in different namespaces. And this template uses a central blacklist where we can add pages and page types where templates should not auto-categorize.