This template is used on 3,430,000+ pages, or roughly 1253% of all pages. To avoid major disruption and server load, any changes should be tested in the template's /sandbox or /testcases subpages, or in your own user subpage. The tested changes can be added to this page in a single edit. Consider discussing changes on the talk page before implementing them.
This hook allows you to add up to ten optional categories, that will be added to a page if a particular parameter is defined. Each category will be added if the corresponding parameter is non-empty. This template displays no visible output, so it can be put anywhere in the template code; common practice is to put it attached to a task force hook, such as |TF_n_HOOK=.