Filters the categories before building the category list.

$categories WP_Term[]

An array of the post's categories.

$post_id int|false

ID of the post to retrieve categories for.
When false, defaults to the current post in the loop.

File: wp-includes/category-template.php. View all references

$categories = apply_filters( 'the_category_list', get_the_category( $post_id ), $post_id );